- Email: [email protected]
Memantine prevents aluminum-induced cognitive deficit in rats
Behavioural Brain Research 225 (2011) 31–38
Contents lists available at ScienceDirect
Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr
Research report
Memantine prevents aluminum-induced cognitive deficit in rats Raafat A. Abdel-Aal ∗ , Abdel-Azim A. Assi, Botros B. Kostandy Department of Pharmacology, Faculty of Medicine, University of Assiut, Egypt
a r t i c l e
i n f o
Article history: Received 16 March 2011 Received in revised form 21 June 2011 Accepted 26 June 2011 Available online 2 July 2011 Keywords: Memantine Aluminum Memory Neuroprotection
a b s t r a c t Memantine, a noncompetitive NMDA receptor blocker, has been demonstrated to be neuroprotective against various neurotoxins. Aluminum, a well-known neurotoxin, has been suggested to be a contributing factor in Alzheimer’s disease. In this study we investigated the possible effect of memantine on aluminum-induced cognitive impairment in rats. Rats were exposed to aluminum chloride (100 mg/kg/day) and memantine (5, 10 and 20 mg/kg/day) for 60 days. Cognitive functions were evaluated using three tests: Morris water maze, radial arm maze and passive avoidance tests. Results showed that memantine failed at low doses to have any significant influence on aluminum-induced memory deficit, but the 20 mg/kg dose was found to cause significant enhancement of memory in the aluminum-exposed rats. This is the first study to demonstrate the protective role of memantine against aluminum-induced neuronal dysfunction. Biochemical and histological investigations are highly indicated to clarify the possible pharmacodynamic basis. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Memantine is a low to moderate uncompetitive N-methylD-aspartate (NMDA) receptor antagonist. It enhances memory in patients with Alzheimer’s disease [1] and offers neuroprotection without eliciting the behavioral or locomotor disturbances produced by NMDA antagonists [2]. In experimental animals, memantine enhanced the cognitive performance in transgenic mouse models of Alzheimer’s disease [3,4] and protected against memory impairment and neurodegeneration induced by beta amyloid protein [5–7]. Memantine ameliorated the memory impairment caused by okadaic [8], quinolinic acids [9] and methamphetamine [10]. Moreover, memantine treatment was found to reduce age-related memory deficits in rats [11], changes caused by bilateral carotid artery occlusion [12] and lipopolysaccharide-induced neuroinflammation [13]. Aluminum, a well-known neurotoxin [14–16], has been implicated in the pathogenesis of Alzheimer’s disease [17–21]. Exposure to aluminum caused neuronal degeneration affecting mainly the cholinergic cells in the brain [22,23]. Various animal studies have shown that aluminum exposure causes neurobehavioral changes resulting in impaired learning and memory ability [24,25]. Here, we investigated the possible protective effect of memantine (if any) on aluminum-induced behavioral changes in rats. Three tests were used to evaluate cognitive functions; Morris water maze,
∗ Corresponding author. Tel.: +20 113591891; fax: +20 882332278. E-mail addresses: raafat [email protected], [email protected] (R.A. Abdel-Aal). 0166-4328/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2011.06.031
radial arm maze and passive avoidance tests. The locomotor functions in animals were assessed using the open field test. Motor coordination was assessed by the rota-rod test. 2. Materials and methods 2.1. Animals Male Wistar rats of 90–100 days old were used. Their weights ranged from 190 to 230 g at the start of treatments. They were supplied from the Assiut Faculty of Medicine Centre of Experimental Animals. They were kept in groups of four in stainless steel cages, in a well-ventilated room under normal dark–light cycle and temperature 22–26 ◦ C with food and water ad libitum. The research design was accepted by the Assiut Faculty of Medicine Scientific Committee. All the experiments were carried out according to the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals. The animals were weighed at the beginning of the experiment, and then weighed on daily basis before treatment until the end of the behavioral evaluation.
2.2. Drugs and treatment schedule Aluminum chloride (AlCl3 ) solution (25 mg/ml) was prepared by dissolving AlCl3 -hexahydrate (Oxford lab. reagents) in sterile water. Rats were injected with AlCl3 intraperitoneally (i.p.) at a dose of 100 mg/kg/day for 60 days before the behavioral tests were started. The dose of aluminum was selected based on our previous trials [25]. Memantine solutions were prepared by dissolving memantine hydrochloride (Sigma–Aldrich, St. Louis, MO, USA) in sterile water in concentrations of 2.5, 5 and 10 mg/ml. Memantine solutions were used for administration of memantine i.p. in doses of 5, 10 and 20 mg/kg/day, respectively. AlCl3 and memantine solutions were freshly prepared before administration. Memantine injections started on the first day of aluminum administration. Injections were given daily at 8:00 AM while behavioral tests were performed at 1:00 PM. The injections of aluminum and memantine were continued throughout the experimental procedures. Control rats received equal volumes of saline i.p.
32
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 2. Pattern of food distribution in the radial arm maze. (
Fig. 1. Schematic representation of different animal groups. ( ) C group, ( ) Al + S, ( ) Al + MEM5, ( ) Al + MEM10, and ( ) Al + MEM20. The numbers inside boxes indicate the number of animals in each group.
2.3. Animal groups (Fig. 1) We utilized 120 animals divided into five groups each containing 24 animals. Group I: control group (C) which received saline i.p. in equal volumes and regimens to aluminum and memantine; Group II: aluminum-intoxicated group (Al + S) which received AlCl3 (100 mg/kg/day i.p.) for 60 days and saline i.p. with equal volumes and regimens to memantine; and Groups III–V: aluminum and memantine-treated groups, which received AlCl3 (100 mg/kg/day i.p.) and memantine for 60 days. Memantine was given in the following doses—Group III: 5 mg/kg/day (Al + MEM5); Group IV: 10 mg/kg/day (Al + MEM10); and Group V: 20 mg/kg/day (Al + MEM20). After 60 days, the animal groups were divided into three subgroups (each containing eight rats) which were evaluated in Morris water maze, radial arm maze and passive avoidance tests, i.e. the animals utilized in a certain cognitive test were not evaluated in any other one (to avoid any contribution of the animals’ experience or training in results of other tests). Eight rats were randomly selected from each animal group and evaluated in open field and rota-rod tests before the start of cognitive tests. 2.4. Behavioral tests 2.4.1. Open field test The test depended on examining the activity of rats when placed in a new environment. The apparatus consisted of a square based wooden box open from above (70 cm × 70 cm base, 25 cm height). The base was divided into 49 equal squares (10 cm × 10 cm). Each rat was placed separately in the apparatus in a fixed corner facing the wall and evaluated for 5 min. The number of squares crossed (floor units which rats crossed with both feet) was regarded as a measure of locomotor activity and the number of rearings (standing on hind limbs) was regarded as a measure of exploratory activity. 2.4.2. Morris water maze The maze consisted of circular stainless steel tank, 160 cm in diameter and 35 cm in height filled with water. The tank was divided by four fixed points on its perimeter into four quadrants. It contained an escape platform (10 cm × 10 cm × 10 cm) kept in a constant quadrant of the pool throughout the trials at a level 1.5 cm below the water surface. The platform was of the same color as tank and the water was rendered opaque with nontoxic white paint (to eliminate any false positive results due to vision). Rats were placed gently at a start point in the middle of the rim of a quadrant not containing the escape area with their face to the wall. If the rat failed to find the escape platform within 90 s, it was gently guided to the platform and allowed to stay on it for 30 s. Each rats had four trials per day separated by 10 min for 5 successive days (acquisition trials) during which three parameters were eval-
) Food particle.
uated; the latency to reach the platform, the distance traveled and the swimming speed. In the 6th day, 24 h after the previous trails, probe trials were started in which the escape platform was removed and the animals were allowed to swim freely for 90 s before the end of the session. In the probe trials, the latency to reach the target quadrant and the time each rat spent in it were calculated. During the different versions of the maze, the animals were monitored by a digital camera fixed 80 cm above the maze and different parameters were analyzed using computer based software (VideoMot2, TSE Systems, Germany). 2.4.3. Radial arm maze test (Fig. 2) This test was conducted in an eight-arm maze made of wood, light brown in color. Each arm of the maze was 15 cm × 15 cm × 70 cm. The arms extended from an octagonal centre compartment that was 30 cm in diameter and of the same level as the arms. The maze was placed on a table in the laboratory 100 cm above the floor with many fixed extra-maze visual cues. Four fixed arms were baited with food pellets (sweetened cereals) in grooves that were located 2 cm from the ends of the arms. Four food pellets were placed just outside the unbaited arms to provide symmetrical food odor all around the maze. This might ensure that arm selection would not be directed by the smell of the food reward. Before the actual training, rats were shaped to run to the ends of the radiating arms and the baits were gradually restricted to grooves. In each trial, after the rat was placed in the central area of the maze, timing had begun and the rat was free to explore. Arm choices were recorded after the rat entered at least half of the length of the arm. The trial was judged complete when the rat chose all baited arms or had spent 10 min. No arm was rebaited after the testing began. Each rat was given two daily trials, 6 days/week for a total of 2.5 weeks, i.e. each rat received 30 trials. Errors were calculated as the number of entries to unbaited arms or re-entering a baited arm. The following parameters were calculated: working memory (the number of repeated entries to baited arms) and reference memory (counting the number of entries to unbaited arms). The score was expressed as the mean number of reference and working memory errors for each group, with data averaged over five blocks, each of six trials. The mean latency required to complete the task in all trials was also calculated. 2.4.4. Passive avoidance test The apparatus consisted of two chambers (20 cm × 25 cm × 30 cm each) separated by a wall containing a communicating hole of 8 cm diameter. One chamber was kept illuminated by a 4 W fluorescent lamp. The test was performed on 2 consecutive days. In acquisition trials (conducted on first day), rats were placed individually in the illuminated chamber and once entered the dark chamber an electric shock (40 V, 0.5 A for 1 s) was delivered to their feet through the floor grid. The rats were immediately removed and returned to the cage. At retention trial, conducted 24 h later, the rats were placed again in the illuminated chamber and the interval between placement in the illuminated chamber and entry to the dark one was recorded (stepthrough latency). If animal did not enter the dark chamber within the 5 min test period, the test was terminated and the step-through latency was recorded as 300 s. 2.4.5. Rota-rod test The apparatus could be described as a treadmill consisting of a rotating drum 7 cm in diameter, 24 cm from the base separated by flanges, rotating in a constant speed of 4/min. rats were placed on the rotating drum up to 5 min. Motor integrity and coordination was assessed by the latency from placement of the animal on the rotating drum until the it fall.
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38 2.5. Statistical analysis Results of the tests were analyzed by one-way or two-way repeated measures ANOVA followed by Bonferonni method as a post-test. Results were represented as mean ± S.E.M. P value < 0.05 was considered significant.
3. Results 3.1. Body weight (Table 1) Repeated-measures ANOVA showed significant difference in the body weight among animal groups [F(4, 70) = 2.56, P < 0.05]. After 60 days, the body weights were significantly increased in all groups, with the exception of Al + S group, which showed non-significant decrease in body weight. Relative to Al + S group, the body weights of different groups were significantly higher. 3.2. Open field test (Fig. 3) One-way ANOVA showed significant differences between animal groups in the number of crossed squares [F(4, 35) = 11.58, P < 0.0001] and the number of rearings [F(4, 35) = 17.64, P < 0.0001]. Al + S group showed significant reductions in crossing and rearings relative to C group. Al + ME5 showed no significant difference from Al + S group, while crossing and rearings were significantly increased in Al + MEM10 and Al + MEM20 groups relative to Al + S group. 3.3. Morris water maze test (Fig. 4) 3.3.1. Acquisition trials Repeated-measures ANOVA showed significant differences among various groups in the time required to reach the platform [F(4, 175) = 29.94, P < 0.0001] and the swimming distance [F(4, 175) = 26.72, P < 0.0001]. No significant difference between different groups was observed regarding the swimming speed [F(4, 175) = 6.22, P = 0.085] (data not shown). Among the 5 successive days there were improvements in the time [factor day: F(4, 56) = 11.08, P < 0.0001] and the distance [factor day: F(4, 56) = 18.92, P < 0.0001] in the C group but not in Al + S group. Relative to Al + S group, significant reductions in the time and the swimming distance were observed in Al + MEM20 but not in Al + MEM5 or Al + MEM10 groups. 3.3.2. Probe trials One-way ANOVA showed significant differences among animal groups in the mean time required to reach the platform area [F(4, 35) = 8.14, P < 0.0001] and the mean time spent in target quadrant [F(4, 35) = 10.85, P < 0.0001]. Both parameters were significantly increased in Al + S group relative to C group. Relative to Al + S group, while Al + MEM5 and Al + MEM10 groups did not show any significant difference, Al + MEM20 group required significantly shorter latency to reach the hidden platform and spent more time in the target quadrant. 3.4. Radial arm maze test (Fig. 5) Repeated-measures ANOVA of the number of errors showed significant differences in the working memory [F(4, 175) = 19.65, P < 0.0001] and the reference memory [F(4, 175) = 29.65, P < 0.0001] among animal groups. The number of errors was significantly higher in Al + S group relative to C group and the number of errors decreased in C group (but not in Al + S group) among successive blocks in reference memory [factor block: F(4, 56) = 16.78, P < 0.0001] and working memory [factor block: F(4, 56) = 18.68, P < 0.0001]. While Al + MEM5 and Al + MEM10 groups did not show
33
any significant difference from Al + S regarding the number of errors, Al + MEM20 group showed significantly lower number of errors relative to Al + S group. One-way ANOVA showed significant difference in latency (time to consume all four rewards) to end the maze among animal groups [F(4, 35) = 12.17, P < 0.0001]. The latency was significantly increased in Al + S group relative to C group. No significant reduction in latency was observed in Al + MEM5 or Al + MEM10 groups relative to Al + S group. In Al + MEM20 group, the latency decreased significantly relative to Al + S group. 3.5. Passive avoidance test (Fig. 6) One-way ANOVA of the step-through latency showed significant differences among various groups [F(4, 35) = 24.51, P < 0.0001]. The step-through latency was significantly lower in C group relative to Al + S group. In Al + MEM5 and Al + MEM10 groups, the step-through latency was not significantly different from Al + S group. The stepthrough latency was significantly higher in Al + MEM20 relative to Al + S group. 3.6. Rota-rod test (Fig. 7) One-way AVOVA showed no significant differences in the latency among animal groups [F(5, 35) = 2.6, P = 0.881]. Al + S group showed no significant difference from C group and none of the memantine-received groups showed any significant difference relative to Al + S group. 4. Discussion Previous studies performed in our laboratory have demonstrated that chronic aluminum intoxication caused significant cognitive impairment in rats. Aluminum impaired the performance of the rats in Morris water maze, radial arm maze and passive avoidance tests. It also decreased exploratory and spontaneous locomotor activity in normal rats without causing any significant impact on motor coordination [25]. In this study, we tried to evaluate the effect of memantine, a well-known neuroprotective agent, on aluminum-induced cognitive deficit in rats. In Morris water maze, aluminum-intoxicated rats which received memantine showed significant reduction in escape latencies during both visible and hidden platform sessions relative to non-treated animals. Moreover, they traveled shorter distances to reach the platform and spent longer time in target quadrant during the probe trials. In the radial arm maze, they showed improvements in the working and reference memories and they ended their missions faster than non-treated animals. Consistent with these results, memantine improved the performance of the aluminum-intoxicated rats in the passive avoidance test as it significantly increased the step-through latency, which means that the aluminum-intoxicated animals were able to retain and retrieve information when they were treated with memantine (they remembered the punishment they experienced a day before). The data shown here demonstrate for the first time that memantine prevented the development of learning and memory deficits due to aluminum intoxication. Memantine also prevented the exploratory and locomotor deficits in the aluminum-intoxicated rats. Interestingly, aluminum-intoxicated rats failed to lose weight when they received memantine. We previously reported that the impaired performance of the aluminum-intoxicated rats in the selected cognitive tests were mostly due to negative effect on learning and memory, excluding any contribution of motor integrity or decreased food motivation in the results of the tests [25]. Here, it is also important to clarify that the observed positive effects of memantine were mostly
34
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Table 1 The body weight (grams) of rats in different groups at the start and after 60 days of treatment. Values are represented as mean ± S.E.M. a P < 0.05 relative to starting body weight. b P < 0.05 relative to Al + S group. Animal groups
Start After 60 days
C
Al + S
Al + MEM5
Al + MEM10
Al + MEM20
214 ± 4.31 241 ± 2.63a,b
218 ± 3.52 198 ± 6.10
213 ± 5.80 230 ± 6.40a,b
216 ± 6.09 233 ± 5.62a,b
211 ± 4.71 239 ± 6.10a,b
Fig. 3. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on crossings (panel a) and the number of rearings (panel b) in the open field test. Values represent mean ± S.E.M. ***P < 0.001 relative to C group. # P < 0.05 and ## P < 0.01 relative to Al + S group.
Fig. 4. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) in Morris water maze test. Acquisition trials; time (s) to reach platform (panel a) and swimming distance (meter) (panel b). Probe trials; time (s) to reach hidden platform quadrant in the probe trial (panel c) and the time spent in hidden platform quadrant (panel d). Values represent mean ± S.E.M. *P < 0.05, **P < 0.01 and ***P < 0.001 relative to C group. # P < 0.05, ## P < 0.01 and ### P < 0.001 relative to Al + S group.
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 5. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on the number of errors in measuring working memory (panel A), the number of errors in measuring reference memory (panel B) and the time required to end the task in radial arm maze (panel C). Values represent mean ± S.E.M. *P < 0.05, **P < 0.01 and ***P < 0.001 relative to C group. # P < 0.05, ## P < 0.01 and ### P < 0.001 relative to Al + S group.
35
due to its ability to enhance cognitive performance and not related to increased locomotor activity or motivation for food. No effect of memantine was found during the early sessions, when the rats had no information about the platform location or the sites of food, which suggests that it did not produce a general effect on the locomotor function or the search pattern itself. This is also consistent with a lack of memantine effect on swimming speed in Morris water maze test. The decreased latency observed in Morris water and radial arm mazes could not be related to increased spontaneous motor activity, as this was not observed in the passive avoidance test, in which memantine prolonged the step-through latency. Therefore, the effect of memantine in the selected tasks most likely represents an improvement in the animals’ spatial learning and memory. Although memantine caused a dose-dependent improvement in cognitive functions in aluminum-exposed rats, significant improvements were only observed at its large dose, i.e. 20 mg/kg/day, the dose previously shown to be neuroprotective in rats [26]. However, the locomotor and exploratory impairments caused by aluminum were evidently prevented by memantine at a dose as low as 10 mg/kg/day and all selected doses of memantine were able to restore weight gaining in rats exposed to aluminum. The effects of memantine on cognitive functions in experimental animals had been evaluated at different doses and durations and so the results were not straightforward. Acute administration of memantine at a dose of 5 mg/kg did not produce any behavioral or motor effects [27], while administration of 10 mg/kg has been shown to induce hyperlocomotion and impaired performance in food-motivated tasks [26,28]. Memantine produced ataxia after an acute dose of 20 mg/kg [26]. Memantine (10 and 20 mg/kg) injected 60 min before or immediately after trainingsession impaired acquisition and retention of aversive memory in the inhibitory avoidance task [29]. Post-training administration of memantine (10 and 20, but not 3 mg/kg) antagonized recognition memory deficits in the rat, suggesting that memantine modulated storage and/or retrieval of information [30]. These results might indicate that low doses of memantine would show the most consistent beneficial effects, whereas high doses might have unwanted detrimental effects on cognitive behavior [31], a hypothesis, our study did not match with. This might be explained that we investigated chronic rather than acute memantine therapy, because this is the mode adopted in the routine therapy of Alzheimer’s disease [32]. Acute administration of large doses of memantine (20–30 mg/kg) can produce very high plasma Cmax values (>10-fold higher than therapeutic) [33] and cause adverse effects such as ataxia, stereotypic behavior and learning impairment [28,34,35]. On the other hand, chronic memantine therapy provides a steady state plasma concentration of the drug
Fig. 6. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on step-through latency (s) in the passive avoidance test. Values represent mean ± S.E.M. ***P < 0.001 relative to C group. ## P < 0.01 relative to Al + S group.
36
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 7. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on the time (s) taken by the rats to fall in the rota-rod test. Values represent mean ± S.E.M.
and prevents the production of peak elevation of the drug level after acute doses [36]. Continuous subcutaneous infusion of memantine (20 mg/kg per day via osmotic pump for 7–14 days), which produces a steady state plasma drug level of approximately 1 M, improves radial maze learning in rats with a lesioned entorhinal cortex, without producing motor side effects observed in acute doses [36]. Chronic memantine treatment (5, 10 and 20 mg/kg) for 14 days did not affect spontaneous locomotor activity in the open field test [37]. Repeated i.p. dosing of memantine (30 mg/kg for 7 days) in mice did not produce any of the sensorimotor adverse effects that were observed following a single i.p. dose of 30 mg/kg [35]. These trials which used chronic memantine therapy mostly demonstrated the development of tolerance to the sensorimotor adverse effects of memantine. This raises the possibility that the positive cognitive functions obtained in our study were mainly due to neuroprotective effect of memantine against aluminum-induced cognitive deficit rather than being due to direct behavioral impacts. Memantine has been shown to exert beneficial effects against cognitive impairments caused by various neurotoxins. Acute memantine treatment (5 mg/kg) prevented methamphetamine induced memory and learning dysfunction [10]. Memantine (1 mg/kg) given for 10 days prevented memory deficit caused by scopolamine in the passive avoidance test [38]. Memantine (20 mg/kg) for 21 days reversed age-induced recognition and memory deficits [11]. Repeated administration of memantine prevented the development of amyloid -induced memory impairments [6], although it was found that memantine at a dose of 20 mg/kg enhanced memory deficits caused by beta amyloid injection with no effect on memory in naïve rats [39] and mild neurotoxic reactions in the rat brain were encountered with the same dose [26]. In our experimental design, AlCl3 was given in dose of 100 mg/kg for 60 days. Such dose and duration were selected to ensure chronic aluminum intoxication and establishment of aluminum-induced neuronal deficit [40–43]. Aluminum-induced behavioral changes had been extensively evaluated with different routes, doses and durations in different species and so the data obtained were generally inconclusive. In previous trials, rats exposed to lower doses or durations of aluminum did not show any behavioral impairment [28]. A methodological criticism that might be raised is that we adopted a dose of aluminum that was far higher than routine human exposure [21], but under certain conditions human may be subjected to extreme levels of aluminum exposure, e.g. occupational aluminum toxicity and dialysis encephalopathy [15,44,45]. Aluminum has long been known to be a neurotoxin. It has been shown to accumulate in all the regions of rat brain following chronic exposure, maximum being in hippocampus which is the site of memory and learning [46–48]. Aluminum exposure was associated with the development of oxidative stress-related damage to
lipids, membrane associated proteins and endogenous antioxidant enzyme activity [49], development of hyperphosphorylated tau [21] and neuronal apoptosis [41]. Aluminum is cholinotoxin [23]. It caused degeneration of cholinergic terminals in cortex and hippocampus [50]. In order to build a preliminary idea about the possible protective mechanism of memantine against aluminum-induced neurotoxicity, it is essential to understand the relationship between aluminum-induced neurotoxicity and glutamate, which is unfortunately, still unclear. On one side, it was found that aluminum increased glutamate release from astrocytes [51] and potentiated the increase in glutamate-induced intracellular calcium overload [52]. It enhanced the excitotoxic damage on rat hippocampal cells [53]. Rats injected with aluminum for 4 weeks showed significant increase in the level of glutamate in the many brain regions: cerebrum, thalamic area, midbrain-hippocampal region and cerebellum [54,55]. From previous data we may conclude that glutamate and its related excitotoxicity might act as a contributing factor in aluminum-induced neuronal dysfunction. On the other side, other studies did not match with this hypothesis. It had been shown that aluminum exposure was associated with increased glutamate uptake by astrocytes and increased conversion to glutamine [56,57]. Aluminum toxicity was found to be independent of calcium or glutamate receptor activation [58]. In another study, aluminum exposure in vitro was not associated with alteration in long term potentiation or glutamate release in rat hippocampal slices [59]. Aluminum also impaired the release of glutamate from transverse rat hippocampal neurons, a mechanism by which aluminum could induce impairment in learning and memory [60]. According to this hypothesis the use of NMDA receptor blockers would further impair glutamatergic transmission and add negative effect on memory, which is in contrast to our results. As this is a pure behavioral study, the dynamics of the protective effect of memantine against aluminum-induced behavioral deficit needs extensive biochemical and histological evaluation. But at least, this is the first study to demonstrate the potential protective effect of memantine against aluminum-induced neurotoxicity. The mechanism by which memantine could protect against aluminum-induced neurotoxicity and behavioral dysfunction might be explained by a variety of factors. Memantine partially normalize information processing in the hippocampus, and when it was given early during the development of the pathology, it conferred neuronal and cognitive protection while indirectly prevented pathological microglial activation [61]. Memantine protected the basal forebrain neurons releasing acetylcholine [62]. It reduced the oxidative damage to proteins in cortex and hippocampus [11] and improved attention and memory of beta amyloid-injected rats [63]. Memantine was able to preserve memory during neuroinflammation [13,61].
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Memantine delayed the progression of symptoms in Alzheimer’s disease patients [1]. The blockade of NMDA receptormediated excitotoxicity can help preserve neuronal structure and function [64–66]. The most significant problem being that at doses that exerted neuroprotective effects, NMDA antagonists caused adverse side effects ranging from memory dysfunction and psychotic reactions in humans [67–69] to acute injury and/or death of neurons in animal brain [70–72]. Memantine is rapidly displaced from the NMDA receptor, which may avoid prolonged receptor blockade and the detrimental effects on learning and memory associated with prolonged blockade of the NMDA receptor [64]. In conclusion, our study showed that memantine could prevent the development of aluminum-induced cognitive deficit if used in appropriate doses, but the possible pharmacological and molecular mechanisms should be fully explored.
References [1] Bullock R. Efficacy and safety of memantine in moderate-to-severe Alzheimer disease: the evidence to date. Alzheimer Dis Assoc Disord 2006;20:23–9. [2] Danysz W, Parsons CG. The NMDA receptor antagonist memantine as a symptomatological and neuroprotective treatment for Alzheimer’s disease: preclinical evidence. Int J Geriatr Psychiatry 2003;18:S23–32. [3] Minkeviciene R, Banerjee P, Tanila H. Memantine improves spatial learning in a transgenic mouse model of Alzheimer’s disease. J Pharmacol Exp Ther 2004;311:677–82. [4] Van Dam D, De Deyn PP. Cognitive evaluation of disease-modifying efficacy of galantamine and memantine in the APP23 model. Eur Neuropsychopharmacol 2006;16:59–69. [5] Miguel-Hidalgo JJ, Alvarez XA, Cacabelos R, Quack G. Neuroprotection by memantine against neurodegeneration induced by beta-amyloid (1-40). Brain Res 2002;958:210–21. [6] Yamada K, Takayanagi M, Kamei H, Nagai T, Dohniwa M, Kobayashi K, et al. Effects of memantine and donepezil on amyloid beta-induced memory impairment in a delayed-matching to position task in rats. Behav Brain Res 2005;162:191–9. [7] Watanabe T, Iwasaki K, Takasaki K, Yamagata N, Fujino M, Nogami A, et al. Dynamin 1 depletion and memory deficits in rats treated with Abeta and cerebral ischemia. J Neurosci Res 2010;88:1908–17. [8] Kamat PK, Tota S, Saxena G, Shukla R, Nath C. Okadaic acid (ICV) induced memory impairment in rats: a suitable experimental model to test anti-dementia activity. Brain Res 2010;1309:66–74. [9] Misztal M, Frankiewicz T, Parsons CG, Danysz W. Learning deficits induced by chronic intraventricular infusion of quinolinic acid—protection by MK-801 and memantine. Eur J Pharmacol 1996;296:1–8. [10] Camarasa J, Rodrigo T, Pubill D, Escubedo E. Memantine is a useful drug to prevent the spatial and non-spatial memory deficits induced by methamphetamine in rats. Pharmacol Res 2010;62:450–6. [11] Pietá Dias C, Martins de Lima MN, Presti-Torres J, Dornelles A, Garcia VA, Siciliani Scalco F, et al. Memantine reduces oxidative damage and enhances long-term recognition memory in aged rats. Neuroscience 2007;146:1719–25. [12] Heim C, Sontag KH. Memantine prevents progressive functional neurodegeneration in rats. J Neural Transm Suppl 1995;46:117–30. [13] Rosi S, Vazdarjanova A, Ramirez-Amaya V, Worley PF, Barnes CA, Wenk GL. Memantine protects against LPS-induced neuroinflammation, restores behaviorally-induced gene expression and spatial learning in the rat. Neuroscience 2006;142:1303–15. [14] Andrási E, Páli N, Molnár Z, Kösel S. Brain aluminum, magnesium and phosphorus contents of control and Alzheimer-diseased patients. J Alzheimers Dis 2005;7:273–84. [15] Wills MR, Savory J. Water content of aluminum, dialysis dementia, and osteomalacia. Environ Health Perspect 1985;63:141–7. [16] Xu N, Majidi V, Markesbery WR, Ehmann WD. Brain aluminum in Alzheimer’s disease using an improved GFAAS method. Neurotoxicology 1992;13:735–43. [17] Gauthier E, Fortier I, Courchesne F, Pepin P, Mortimer J, Gauvreau D. Aluminum forms in drinking water and risk of Alzheimer’s disease. Environ Res 2000;84:234–46. [18] Lukiw WJ. Alzheimer’s disease and aluminium. In: Yasui M, Strong MJ, Ota K, Verity MA, editors. Mineral and metal neurotoxicology. New York: CRC Press; 1997. p. 113–26. [19] Schnabel J. Alzheimer’s disease: arthritis of the brain? New Sci 1992;138:22–6. [20] Smith MA, Sayre LM, Monnier VM, Perry G. Radical AGEing in Alzheimer’s disease. Trends Neurosci 1995;18:172–6. [21] Walton JR. An aluminum-based rat model for Alzheimer’s disease exhibits oxidative damage, inhibition of PP2A activity, hyperphosphorylated tau, and granulovacuolar degeneration. J Inorg Biochem 2007;101:1275–84. [22] Bilkei-Gorzó A. Neurotoxic effect of enteral aluminium. Food Chem Toxicol 1993;31:357–61. [23] Gulya K, Rakonczay Z, Kása P. Cholinotoxic effects of aluminium in rat brain. J Neurochem 1990;54:1020–6.
37
[24] Shuchang H, Qiao N, Piye N, Mingwei H, Xiaoshu S, Feng S, et al. Protective effects of gastrodia elata on aluminium-chloride-induced learning impairments and alterations of amino acid neurotransmitter release in adult rats. Restor Neurol Neurosci 2008;26:467–73. [25] Abdel-Aal RA, Assi AA, Kostandy BB. Rivastigmine reverses aluminum-induced behavioral changes in rats. Eur J Pharmacol 2011;659:169–76. [26] Creeley C, Wozniak DF, Labruyere J, Taylor GT, Olney JW. Low doses of memantine disrupt memory in adult rats. J Neurosci 2006;26:3923–32. [27] Van Dam D, Abramowski D, Staufenbiel M, De Deyn PP. Symptomatic effect of donepezil, rivastigmine, galantamine and memantine on cognitive deficits in the APP23 model. Psychopharmacology 2005;180:177–90. [28] Sukhanov IM, Zakharova ES, Danysz W, Bespalov AY. Effects of NMDA receptor channel blockers, MK-801 and memantine, on locomotor activity and tolerance to delay of reward in Wistar-Kyoto and spontaneously hypertensive rats. Behav Pharmacol 2004;15:263–71. [29] Réus GZ, Valvassori SS, Machado RA, Martins MR, Gavioli EC, Quevedo J. Acute treatment with low doses of memantine does not impair aversive, non-associative and recognition memory in rats. Naunyn Schmiedebergs Arch Pharmacol 2008;376:295–300. [30] Pitsikas N, Sakellaridis N. Memantine and recognition memory: possible facilitation of its behavioral effects by the nitric oxide (NO) donor molsidomine. Eur J Pharmacol 2007;571:174–9. [31] Yuedea CM, Dong H, Csernansky JG. Anti-dementia drugs and hippocampaldependent memory in rodents. Behav Pharmacol 2007;18:347–63. [32] Doody RS, Tariot PN, Pfeiffer E, Olin JT, Graham SM. Meta-analysis of six-month memantine trials in Alzheimer’s disease. Alzheimers Dement 2007;3:7–17. [33] Danysz W, Parsons CG, Kornhuber J, Schmidt WJ, Quack G. Aminoadamantanes as NMDA receptor antagonists and antiparkinsonian agents—preclinical studies. Neurosci Biobehav Rev 1997;21:455–68. [34] Danysz W, Essmann U, Bresink I, Wilke R. Glutamate antagonists have different effects on spontaneous locomotor activity in rats. Pharmacol Biochem Behav 1994;48:111–8. [35] Kos T, Popik P. A comparison of the predictive therapeutic and undesired side effects of the NMDA receptor antagonist, memantine, in mice. Behav Pharmacol 2005;16:155–61. [36] Zajaczkowski W, Quack G, Danysz W. Infusion of (+)-MK-801 and memantinecontrasting effects on radial maze learning in rats with entorhinal cortex lesion. Eur J Pharmacol 1996;296:239–46. [37] Réus GZ, Stringari RB, Kirsch TR, Fries GR, Kapczinski F, Roesler R, et al. Neurochemical and behavioural effects of acute and chronic memantine administration in rats: further support for NMDA as a new pharmacological target for the treatment of depression? Brain Res Bull 2010;81:585–9. [38] Garibova TL, Voronina TA, Litvinova SA, Kuznetsova AL, Kul’chikov AE, Alesenko AV. Features of memantine action profile in cholinergic deficit and intracerebral posttraumatic hematoma (hemorrhagic stroke) models in rats. Eksp Klin Farmakol 2008;71:8–13 [abstract]. [39] Nakamura S, Murayama N, Noshita T, Katsuragi R, Ohno T. Cognitive dysfunction induced by sequential injection of amyloid-beta and ibotenate into the bilateral hippocampus; protection by memantine and MK-801. Eur J Pharmacol 2006;548:115–22. [40] Kawahara M, Kato M, Kuroda Y. Effects of aluminum on the neurotoxicity of primary cultured neurons and on the aggregation of beta-amyloid protein. Brain Res Bull 2001;55:211–7. [41] Niu Q, Yang Y, Zhang Q, Niu P, He S, Di Gioacchino M, et al. The relationship between Bcl-gene expression and learning and memory impairment in chronic aluminum-exposed rats. Neurotox Res 2007;12:163–9. [42] Sun X, Liu Z, Zhang X, Zhang Z. Effects of aluminum on the number of neurons granulovacuolar degeneration in rats. Wei Sheng Yan Jiu 1999;28:164–6 [abstract]. [43] Connor DJ, Jope RS, Harrell LE. Chronic, oral aluminum administration to rats: cognition and cholinergic parameters. Pharmacol Biochem Behav 1988;31:467–74. [44] Flaten TP, Alfrey AC, Birchall JD, Savory J, Yokel RA. Status and future concerns of clinical and environmental aluminum toxicology. J Toxicol Environ Health 1996;48:527–41. [45] Schlatter C. Biomedical aspects of aluminium. Med Lav 1992;83:470–4. [46] Julka D, Vasishta RK, Gill KD. Distribution of aluminum in different regions and body organs of rat. Biol Trace Elem Res 1996;52:181–92. [47] Kaur A, Joshi K, Minz RM, Gill KD. Neurofilament phosphorylation and disruption: a possible mechanism of chronic aluminium toxicity in Wistar rats. Toxicology 2006;219:1–10. [48] Lal B, Gupta A, Gupta A, Murthy RC, Ali MM, Chandra SV. Aluminium ingestion alters behavior and some neurochemicals in rats. Indian J Exp Biol 1993;31:30–5. [49] Sethi P, Jyoti A, Singh R, Hussain E, Sharma D. Aluminium-induced electrophysiological, biochemical and cognitive modifications in the hippocampus of aging rats. Neurotoxicology 2008;29:1069–79. [50] Platt B, Fiddler G, Riedel G, Henderson Z. Aluminium toxicity in the rat brain: histochemical and immunocytochemical evidence. Brain Res Bull 2001;55:257–67. [51] Albrecht J, Simmons M, Dutton GR, Norenberg MD. Aluminum chloride stimulates the release of endogenous glutamate, taurine and adenosine from cultured rat cortical astrocytes. Neurosci Lett 1991;127:105–7. [52] Mundy WR, Freudenrich TM, Kodavanti PR. Aluminum potentiates glutamateinduced calcium accumulation and iron-induced oxygen free radical formation in primary neuronal cultures. Mol Chem Neuropathol 1997;32:41–57.
38
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
[53] Matyja E. Aluminum enhances glutamate-mediated neurotoxicity in organotypic cultures of rat hippocampus. Folia Neuropathol 2000;38:47–53. [54] El-Rahman SS. Neuropathology of aluminum toxicity in rats (glutamate and GABA impairment). Pharmacol Res 2003;47:189–94. [55] Nayak P, Chatterjee AK. Effects of aluminium exposure on brain glutamate and GABA systems: an experimental study in rats. Food Chem Toxicol 2001;39:1285–9. [56] Struys-Ponsar C, Guillard O, van den Bosch de Aguilar P. Effects of aluminum exposure on glutamate metabolism: a possible explanation for its toxicity. Exp Neurol 2000;163:157–64. [57] Zielke HR, Jackson MJ, Tildon JT, Max SR. A glutamatergic mechanism for aluminum toxicity in astrocytes. Mol Chem Neuropathol 1993;19:219–33. [58] Brenner SR, Yoon KW. Aluminum toxicity in rat hippocampal neurons. Neurosci Lett 1994;178:260–2. [59] Gilbert ME, Shafer TJ. In vitro exposure to aluminum does not alter long-term potentiation or glutamate release in rat hippocampal slices. Neurotoxicol Teratol 1996;18:175–80. [60] Provan SD, Yokel RA. Aluminum inhibits glutamate release from transverse rat hippocampal slices: role of G proteins, Ca channels and protein kinase C. Neurotoxicology 1992;13:413–20. [61] Rosi S, Ramirez-Amaya V, Vazdarjanova A, Esparza EE, Larkin PB, Fike JR, et al. Accuracy of hippocampal network activity is disrupted by neuroinflammation: rescue by memantine. Brain 2009;132:2464–77. [62] Wenk GL, Zajaczkowski W, Danysz W. Neuroprotection of acetylcholinergic basal forebrain neurons by memantine and neurokinin B. Behav Brain Res 1997;83:129–33. [63] Nyakas C, Granic I, Halmy LG, Banerjee P, Luiten PG. The basal forebrain cholinergic system in ageing and dementia, rescuing cholinergic neurons from neurotoxic amyloid-beta42 with memantine. Behav Brain Res 2010;221:594–603.
[64] Lipton SA. Paradigm shift in neuroprotection by NMDA receptor blockade: memantine and beyond. Nat Rev Drug Discov 2006;5:160–70. [65] Lipton SA. Pathologically-activated therapeutics for neuroprotection: mechanism of NMDA receptor block by memantine and S-nitrosylation. Curr Drug Targets 2007;8:621–32. [66] Wenk GL, Parsons CG, Danysz W. Potential role of N-methyl-d-aspartate receptors as executors of neurodegeneration resulting from diverse insults: focus on memantine. Behav Pharmacol 2006;17:411–24. [67] Grotta J, Clark W, Coull B, Pettigrew LC, Mackay B, Goldstein LB, et al. Safety and tolerability of the glutamate antagonist CGS 19755 (Selfotel) in patients with acute ischemic stroke. Results of a phase IIa randomized trial. Stroke 1995;26:602–5. [68] Herrling PL. D-CPPene (SDZ EAA 494), a competitive NMDA antagonist: results from animal models and first results in humans. Neuropsychopharmacology 1994;10:591S. [69] Krystal JH, Karper LP, Seibyl JP, Freeman GK, Delaney R, Bremner JD, et al. Subanesthetic effects of the noncompetitive NMDA antagonist, ketamine, in humans. Psychotomimetic, perceptual, cognitive, and neuroendocrine responses. Arch Gen Psychiatry 1994;51:199–214. [70] Fix AS, Horn JW, Wightman KA, Johnson CA, Long GG, Storts RW, et al. Neuronal vacuolization and necrosis induced by the noncompetitive N-methylD-aspartate (NMDA) antagonist MK(+)801 (dizocilpine maleate): a light and electron microscopic evaluation of the rat retrosplenial cortex. Exp Neurol 1993;123:204–15. [71] Olney JW, Labruyere J, Wang G, Wozniak DF, Price MT, Sesma MA. NMDA antagonist neurotoxicity: mechanism and prevention. Science 1991;254:1515–8. [72] Wozniak DF, Dikranian K, Ishimaru MJ, Nardi A, Corso TD, Tenkova T, et al. Disseminated corticolimbic neuronal degeneration induced in rat brain by MK801: potential relevance to Alzheimer’s disease. Neurobiol Dis 1998;5:305–22.
Contents lists available at ScienceDirect
Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr
Research report
Memantine prevents aluminum-induced cognitive deficit in rats Raafat A. Abdel-Aal ∗ , Abdel-Azim A. Assi, Botros B. Kostandy Department of Pharmacology, Faculty of Medicine, University of Assiut, Egypt
a r t i c l e
i n f o
Article history: Received 16 March 2011 Received in revised form 21 June 2011 Accepted 26 June 2011 Available online 2 July 2011 Keywords: Memantine Aluminum Memory Neuroprotection
a b s t r a c t Memantine, a noncompetitive NMDA receptor blocker, has been demonstrated to be neuroprotective against various neurotoxins. Aluminum, a well-known neurotoxin, has been suggested to be a contributing factor in Alzheimer’s disease. In this study we investigated the possible effect of memantine on aluminum-induced cognitive impairment in rats. Rats were exposed to aluminum chloride (100 mg/kg/day) and memantine (5, 10 and 20 mg/kg/day) for 60 days. Cognitive functions were evaluated using three tests: Morris water maze, radial arm maze and passive avoidance tests. Results showed that memantine failed at low doses to have any significant influence on aluminum-induced memory deficit, but the 20 mg/kg dose was found to cause significant enhancement of memory in the aluminum-exposed rats. This is the first study to demonstrate the protective role of memantine against aluminum-induced neuronal dysfunction. Biochemical and histological investigations are highly indicated to clarify the possible pharmacodynamic basis. © 2011 Elsevier B.V. All rights reserved.
1. Introduction Memantine is a low to moderate uncompetitive N-methylD-aspartate (NMDA) receptor antagonist. It enhances memory in patients with Alzheimer’s disease [1] and offers neuroprotection without eliciting the behavioral or locomotor disturbances produced by NMDA antagonists [2]. In experimental animals, memantine enhanced the cognitive performance in transgenic mouse models of Alzheimer’s disease [3,4] and protected against memory impairment and neurodegeneration induced by beta amyloid protein [5–7]. Memantine ameliorated the memory impairment caused by okadaic [8], quinolinic acids [9] and methamphetamine [10]. Moreover, memantine treatment was found to reduce age-related memory deficits in rats [11], changes caused by bilateral carotid artery occlusion [12] and lipopolysaccharide-induced neuroinflammation [13]. Aluminum, a well-known neurotoxin [14–16], has been implicated in the pathogenesis of Alzheimer’s disease [17–21]. Exposure to aluminum caused neuronal degeneration affecting mainly the cholinergic cells in the brain [22,23]. Various animal studies have shown that aluminum exposure causes neurobehavioral changes resulting in impaired learning and memory ability [24,25]. Here, we investigated the possible protective effect of memantine (if any) on aluminum-induced behavioral changes in rats. Three tests were used to evaluate cognitive functions; Morris water maze,
∗ Corresponding author. Tel.: +20 113591891; fax: +20 882332278. E-mail addresses: raafat [email protected], [email protected] (R.A. Abdel-Aal). 0166-4328/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2011.06.031
radial arm maze and passive avoidance tests. The locomotor functions in animals were assessed using the open field test. Motor coordination was assessed by the rota-rod test. 2. Materials and methods 2.1. Animals Male Wistar rats of 90–100 days old were used. Their weights ranged from 190 to 230 g at the start of treatments. They were supplied from the Assiut Faculty of Medicine Centre of Experimental Animals. They were kept in groups of four in stainless steel cages, in a well-ventilated room under normal dark–light cycle and temperature 22–26 ◦ C with food and water ad libitum. The research design was accepted by the Assiut Faculty of Medicine Scientific Committee. All the experiments were carried out according to the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals. The animals were weighed at the beginning of the experiment, and then weighed on daily basis before treatment until the end of the behavioral evaluation.
2.2. Drugs and treatment schedule Aluminum chloride (AlCl3 ) solution (25 mg/ml) was prepared by dissolving AlCl3 -hexahydrate (Oxford lab. reagents) in sterile water. Rats were injected with AlCl3 intraperitoneally (i.p.) at a dose of 100 mg/kg/day for 60 days before the behavioral tests were started. The dose of aluminum was selected based on our previous trials [25]. Memantine solutions were prepared by dissolving memantine hydrochloride (Sigma–Aldrich, St. Louis, MO, USA) in sterile water in concentrations of 2.5, 5 and 10 mg/ml. Memantine solutions were used for administration of memantine i.p. in doses of 5, 10 and 20 mg/kg/day, respectively. AlCl3 and memantine solutions were freshly prepared before administration. Memantine injections started on the first day of aluminum administration. Injections were given daily at 8:00 AM while behavioral tests were performed at 1:00 PM. The injections of aluminum and memantine were continued throughout the experimental procedures. Control rats received equal volumes of saline i.p.
32
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 2. Pattern of food distribution in the radial arm maze. (
Fig. 1. Schematic representation of different animal groups. ( ) C group, ( ) Al + S, ( ) Al + MEM5, ( ) Al + MEM10, and ( ) Al + MEM20. The numbers inside boxes indicate the number of animals in each group.
2.3. Animal groups (Fig. 1) We utilized 120 animals divided into five groups each containing 24 animals. Group I: control group (C) which received saline i.p. in equal volumes and regimens to aluminum and memantine; Group II: aluminum-intoxicated group (Al + S) which received AlCl3 (100 mg/kg/day i.p.) for 60 days and saline i.p. with equal volumes and regimens to memantine; and Groups III–V: aluminum and memantine-treated groups, which received AlCl3 (100 mg/kg/day i.p.) and memantine for 60 days. Memantine was given in the following doses—Group III: 5 mg/kg/day (Al + MEM5); Group IV: 10 mg/kg/day (Al + MEM10); and Group V: 20 mg/kg/day (Al + MEM20). After 60 days, the animal groups were divided into three subgroups (each containing eight rats) which were evaluated in Morris water maze, radial arm maze and passive avoidance tests, i.e. the animals utilized in a certain cognitive test were not evaluated in any other one (to avoid any contribution of the animals’ experience or training in results of other tests). Eight rats were randomly selected from each animal group and evaluated in open field and rota-rod tests before the start of cognitive tests. 2.4. Behavioral tests 2.4.1. Open field test The test depended on examining the activity of rats when placed in a new environment. The apparatus consisted of a square based wooden box open from above (70 cm × 70 cm base, 25 cm height). The base was divided into 49 equal squares (10 cm × 10 cm). Each rat was placed separately in the apparatus in a fixed corner facing the wall and evaluated for 5 min. The number of squares crossed (floor units which rats crossed with both feet) was regarded as a measure of locomotor activity and the number of rearings (standing on hind limbs) was regarded as a measure of exploratory activity. 2.4.2. Morris water maze The maze consisted of circular stainless steel tank, 160 cm in diameter and 35 cm in height filled with water. The tank was divided by four fixed points on its perimeter into four quadrants. It contained an escape platform (10 cm × 10 cm × 10 cm) kept in a constant quadrant of the pool throughout the trials at a level 1.5 cm below the water surface. The platform was of the same color as tank and the water was rendered opaque with nontoxic white paint (to eliminate any false positive results due to vision). Rats were placed gently at a start point in the middle of the rim of a quadrant not containing the escape area with their face to the wall. If the rat failed to find the escape platform within 90 s, it was gently guided to the platform and allowed to stay on it for 30 s. Each rats had four trials per day separated by 10 min for 5 successive days (acquisition trials) during which three parameters were eval-
) Food particle.
uated; the latency to reach the platform, the distance traveled and the swimming speed. In the 6th day, 24 h after the previous trails, probe trials were started in which the escape platform was removed and the animals were allowed to swim freely for 90 s before the end of the session. In the probe trials, the latency to reach the target quadrant and the time each rat spent in it were calculated. During the different versions of the maze, the animals were monitored by a digital camera fixed 80 cm above the maze and different parameters were analyzed using computer based software (VideoMot2, TSE Systems, Germany). 2.4.3. Radial arm maze test (Fig. 2) This test was conducted in an eight-arm maze made of wood, light brown in color. Each arm of the maze was 15 cm × 15 cm × 70 cm. The arms extended from an octagonal centre compartment that was 30 cm in diameter and of the same level as the arms. The maze was placed on a table in the laboratory 100 cm above the floor with many fixed extra-maze visual cues. Four fixed arms were baited with food pellets (sweetened cereals) in grooves that were located 2 cm from the ends of the arms. Four food pellets were placed just outside the unbaited arms to provide symmetrical food odor all around the maze. This might ensure that arm selection would not be directed by the smell of the food reward. Before the actual training, rats were shaped to run to the ends of the radiating arms and the baits were gradually restricted to grooves. In each trial, after the rat was placed in the central area of the maze, timing had begun and the rat was free to explore. Arm choices were recorded after the rat entered at least half of the length of the arm. The trial was judged complete when the rat chose all baited arms or had spent 10 min. No arm was rebaited after the testing began. Each rat was given two daily trials, 6 days/week for a total of 2.5 weeks, i.e. each rat received 30 trials. Errors were calculated as the number of entries to unbaited arms or re-entering a baited arm. The following parameters were calculated: working memory (the number of repeated entries to baited arms) and reference memory (counting the number of entries to unbaited arms). The score was expressed as the mean number of reference and working memory errors for each group, with data averaged over five blocks, each of six trials. The mean latency required to complete the task in all trials was also calculated. 2.4.4. Passive avoidance test The apparatus consisted of two chambers (20 cm × 25 cm × 30 cm each) separated by a wall containing a communicating hole of 8 cm diameter. One chamber was kept illuminated by a 4 W fluorescent lamp. The test was performed on 2 consecutive days. In acquisition trials (conducted on first day), rats were placed individually in the illuminated chamber and once entered the dark chamber an electric shock (40 V, 0.5 A for 1 s) was delivered to their feet through the floor grid. The rats were immediately removed and returned to the cage. At retention trial, conducted 24 h later, the rats were placed again in the illuminated chamber and the interval between placement in the illuminated chamber and entry to the dark one was recorded (stepthrough latency). If animal did not enter the dark chamber within the 5 min test period, the test was terminated and the step-through latency was recorded as 300 s. 2.4.5. Rota-rod test The apparatus could be described as a treadmill consisting of a rotating drum 7 cm in diameter, 24 cm from the base separated by flanges, rotating in a constant speed of 4/min. rats were placed on the rotating drum up to 5 min. Motor integrity and coordination was assessed by the latency from placement of the animal on the rotating drum until the it fall.
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38 2.5. Statistical analysis Results of the tests were analyzed by one-way or two-way repeated measures ANOVA followed by Bonferonni method as a post-test. Results were represented as mean ± S.E.M. P value < 0.05 was considered significant.
3. Results 3.1. Body weight (Table 1) Repeated-measures ANOVA showed significant difference in the body weight among animal groups [F(4, 70) = 2.56, P < 0.05]. After 60 days, the body weights were significantly increased in all groups, with the exception of Al + S group, which showed non-significant decrease in body weight. Relative to Al + S group, the body weights of different groups were significantly higher. 3.2. Open field test (Fig. 3) One-way ANOVA showed significant differences between animal groups in the number of crossed squares [F(4, 35) = 11.58, P < 0.0001] and the number of rearings [F(4, 35) = 17.64, P < 0.0001]. Al + S group showed significant reductions in crossing and rearings relative to C group. Al + ME5 showed no significant difference from Al + S group, while crossing and rearings were significantly increased in Al + MEM10 and Al + MEM20 groups relative to Al + S group. 3.3. Morris water maze test (Fig. 4) 3.3.1. Acquisition trials Repeated-measures ANOVA showed significant differences among various groups in the time required to reach the platform [F(4, 175) = 29.94, P < 0.0001] and the swimming distance [F(4, 175) = 26.72, P < 0.0001]. No significant difference between different groups was observed regarding the swimming speed [F(4, 175) = 6.22, P = 0.085] (data not shown). Among the 5 successive days there were improvements in the time [factor day: F(4, 56) = 11.08, P < 0.0001] and the distance [factor day: F(4, 56) = 18.92, P < 0.0001] in the C group but not in Al + S group. Relative to Al + S group, significant reductions in the time and the swimming distance were observed in Al + MEM20 but not in Al + MEM5 or Al + MEM10 groups. 3.3.2. Probe trials One-way ANOVA showed significant differences among animal groups in the mean time required to reach the platform area [F(4, 35) = 8.14, P < 0.0001] and the mean time spent in target quadrant [F(4, 35) = 10.85, P < 0.0001]. Both parameters were significantly increased in Al + S group relative to C group. Relative to Al + S group, while Al + MEM5 and Al + MEM10 groups did not show any significant difference, Al + MEM20 group required significantly shorter latency to reach the hidden platform and spent more time in the target quadrant. 3.4. Radial arm maze test (Fig. 5) Repeated-measures ANOVA of the number of errors showed significant differences in the working memory [F(4, 175) = 19.65, P < 0.0001] and the reference memory [F(4, 175) = 29.65, P < 0.0001] among animal groups. The number of errors was significantly higher in Al + S group relative to C group and the number of errors decreased in C group (but not in Al + S group) among successive blocks in reference memory [factor block: F(4, 56) = 16.78, P < 0.0001] and working memory [factor block: F(4, 56) = 18.68, P < 0.0001]. While Al + MEM5 and Al + MEM10 groups did not show
33
any significant difference from Al + S regarding the number of errors, Al + MEM20 group showed significantly lower number of errors relative to Al + S group. One-way ANOVA showed significant difference in latency (time to consume all four rewards) to end the maze among animal groups [F(4, 35) = 12.17, P < 0.0001]. The latency was significantly increased in Al + S group relative to C group. No significant reduction in latency was observed in Al + MEM5 or Al + MEM10 groups relative to Al + S group. In Al + MEM20 group, the latency decreased significantly relative to Al + S group. 3.5. Passive avoidance test (Fig. 6) One-way ANOVA of the step-through latency showed significant differences among various groups [F(4, 35) = 24.51, P < 0.0001]. The step-through latency was significantly lower in C group relative to Al + S group. In Al + MEM5 and Al + MEM10 groups, the step-through latency was not significantly different from Al + S group. The stepthrough latency was significantly higher in Al + MEM20 relative to Al + S group. 3.6. Rota-rod test (Fig. 7) One-way AVOVA showed no significant differences in the latency among animal groups [F(5, 35) = 2.6, P = 0.881]. Al + S group showed no significant difference from C group and none of the memantine-received groups showed any significant difference relative to Al + S group. 4. Discussion Previous studies performed in our laboratory have demonstrated that chronic aluminum intoxication caused significant cognitive impairment in rats. Aluminum impaired the performance of the rats in Morris water maze, radial arm maze and passive avoidance tests. It also decreased exploratory and spontaneous locomotor activity in normal rats without causing any significant impact on motor coordination [25]. In this study, we tried to evaluate the effect of memantine, a well-known neuroprotective agent, on aluminum-induced cognitive deficit in rats. In Morris water maze, aluminum-intoxicated rats which received memantine showed significant reduction in escape latencies during both visible and hidden platform sessions relative to non-treated animals. Moreover, they traveled shorter distances to reach the platform and spent longer time in target quadrant during the probe trials. In the radial arm maze, they showed improvements in the working and reference memories and they ended their missions faster than non-treated animals. Consistent with these results, memantine improved the performance of the aluminum-intoxicated rats in the passive avoidance test as it significantly increased the step-through latency, which means that the aluminum-intoxicated animals were able to retain and retrieve information when they were treated with memantine (they remembered the punishment they experienced a day before). The data shown here demonstrate for the first time that memantine prevented the development of learning and memory deficits due to aluminum intoxication. Memantine also prevented the exploratory and locomotor deficits in the aluminum-intoxicated rats. Interestingly, aluminum-intoxicated rats failed to lose weight when they received memantine. We previously reported that the impaired performance of the aluminum-intoxicated rats in the selected cognitive tests were mostly due to negative effect on learning and memory, excluding any contribution of motor integrity or decreased food motivation in the results of the tests [25]. Here, it is also important to clarify that the observed positive effects of memantine were mostly
34
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Table 1 The body weight (grams) of rats in different groups at the start and after 60 days of treatment. Values are represented as mean ± S.E.M. a P < 0.05 relative to starting body weight. b P < 0.05 relative to Al + S group. Animal groups
Start After 60 days
C
Al + S
Al + MEM5
Al + MEM10
Al + MEM20
214 ± 4.31 241 ± 2.63a,b
218 ± 3.52 198 ± 6.10
213 ± 5.80 230 ± 6.40a,b
216 ± 6.09 233 ± 5.62a,b
211 ± 4.71 239 ± 6.10a,b
Fig. 3. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on crossings (panel a) and the number of rearings (panel b) in the open field test. Values represent mean ± S.E.M. ***P < 0.001 relative to C group. # P < 0.05 and ## P < 0.01 relative to Al + S group.
Fig. 4. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) in Morris water maze test. Acquisition trials; time (s) to reach platform (panel a) and swimming distance (meter) (panel b). Probe trials; time (s) to reach hidden platform quadrant in the probe trial (panel c) and the time spent in hidden platform quadrant (panel d). Values represent mean ± S.E.M. *P < 0.05, **P < 0.01 and ***P < 0.001 relative to C group. # P < 0.05, ## P < 0.01 and ### P < 0.001 relative to Al + S group.
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 5. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on the number of errors in measuring working memory (panel A), the number of errors in measuring reference memory (panel B) and the time required to end the task in radial arm maze (panel C). Values represent mean ± S.E.M. *P < 0.05, **P < 0.01 and ***P < 0.001 relative to C group. # P < 0.05, ## P < 0.01 and ### P < 0.001 relative to Al + S group.
35
due to its ability to enhance cognitive performance and not related to increased locomotor activity or motivation for food. No effect of memantine was found during the early sessions, when the rats had no information about the platform location or the sites of food, which suggests that it did not produce a general effect on the locomotor function or the search pattern itself. This is also consistent with a lack of memantine effect on swimming speed in Morris water maze test. The decreased latency observed in Morris water and radial arm mazes could not be related to increased spontaneous motor activity, as this was not observed in the passive avoidance test, in which memantine prolonged the step-through latency. Therefore, the effect of memantine in the selected tasks most likely represents an improvement in the animals’ spatial learning and memory. Although memantine caused a dose-dependent improvement in cognitive functions in aluminum-exposed rats, significant improvements were only observed at its large dose, i.e. 20 mg/kg/day, the dose previously shown to be neuroprotective in rats [26]. However, the locomotor and exploratory impairments caused by aluminum were evidently prevented by memantine at a dose as low as 10 mg/kg/day and all selected doses of memantine were able to restore weight gaining in rats exposed to aluminum. The effects of memantine on cognitive functions in experimental animals had been evaluated at different doses and durations and so the results were not straightforward. Acute administration of memantine at a dose of 5 mg/kg did not produce any behavioral or motor effects [27], while administration of 10 mg/kg has been shown to induce hyperlocomotion and impaired performance in food-motivated tasks [26,28]. Memantine produced ataxia after an acute dose of 20 mg/kg [26]. Memantine (10 and 20 mg/kg) injected 60 min before or immediately after trainingsession impaired acquisition and retention of aversive memory in the inhibitory avoidance task [29]. Post-training administration of memantine (10 and 20, but not 3 mg/kg) antagonized recognition memory deficits in the rat, suggesting that memantine modulated storage and/or retrieval of information [30]. These results might indicate that low doses of memantine would show the most consistent beneficial effects, whereas high doses might have unwanted detrimental effects on cognitive behavior [31], a hypothesis, our study did not match with. This might be explained that we investigated chronic rather than acute memantine therapy, because this is the mode adopted in the routine therapy of Alzheimer’s disease [32]. Acute administration of large doses of memantine (20–30 mg/kg) can produce very high plasma Cmax values (>10-fold higher than therapeutic) [33] and cause adverse effects such as ataxia, stereotypic behavior and learning impairment [28,34,35]. On the other hand, chronic memantine therapy provides a steady state plasma concentration of the drug
Fig. 6. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on step-through latency (s) in the passive avoidance test. Values represent mean ± S.E.M. ***P < 0.001 relative to C group. ## P < 0.01 relative to Al + S group.
36
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Fig. 7. Effects of aluminum and combined treatment by memantine (5, 10 and 20 mg/kg) on the time (s) taken by the rats to fall in the rota-rod test. Values represent mean ± S.E.M.
and prevents the production of peak elevation of the drug level after acute doses [36]. Continuous subcutaneous infusion of memantine (20 mg/kg per day via osmotic pump for 7–14 days), which produces a steady state plasma drug level of approximately 1 M, improves radial maze learning in rats with a lesioned entorhinal cortex, without producing motor side effects observed in acute doses [36]. Chronic memantine treatment (5, 10 and 20 mg/kg) for 14 days did not affect spontaneous locomotor activity in the open field test [37]. Repeated i.p. dosing of memantine (30 mg/kg for 7 days) in mice did not produce any of the sensorimotor adverse effects that were observed following a single i.p. dose of 30 mg/kg [35]. These trials which used chronic memantine therapy mostly demonstrated the development of tolerance to the sensorimotor adverse effects of memantine. This raises the possibility that the positive cognitive functions obtained in our study were mainly due to neuroprotective effect of memantine against aluminum-induced cognitive deficit rather than being due to direct behavioral impacts. Memantine has been shown to exert beneficial effects against cognitive impairments caused by various neurotoxins. Acute memantine treatment (5 mg/kg) prevented methamphetamine induced memory and learning dysfunction [10]. Memantine (1 mg/kg) given for 10 days prevented memory deficit caused by scopolamine in the passive avoidance test [38]. Memantine (20 mg/kg) for 21 days reversed age-induced recognition and memory deficits [11]. Repeated administration of memantine prevented the development of amyloid -induced memory impairments [6], although it was found that memantine at a dose of 20 mg/kg enhanced memory deficits caused by beta amyloid injection with no effect on memory in naïve rats [39] and mild neurotoxic reactions in the rat brain were encountered with the same dose [26]. In our experimental design, AlCl3 was given in dose of 100 mg/kg for 60 days. Such dose and duration were selected to ensure chronic aluminum intoxication and establishment of aluminum-induced neuronal deficit [40–43]. Aluminum-induced behavioral changes had been extensively evaluated with different routes, doses and durations in different species and so the data obtained were generally inconclusive. In previous trials, rats exposed to lower doses or durations of aluminum did not show any behavioral impairment [28]. A methodological criticism that might be raised is that we adopted a dose of aluminum that was far higher than routine human exposure [21], but under certain conditions human may be subjected to extreme levels of aluminum exposure, e.g. occupational aluminum toxicity and dialysis encephalopathy [15,44,45]. Aluminum has long been known to be a neurotoxin. It has been shown to accumulate in all the regions of rat brain following chronic exposure, maximum being in hippocampus which is the site of memory and learning [46–48]. Aluminum exposure was associated with the development of oxidative stress-related damage to
lipids, membrane associated proteins and endogenous antioxidant enzyme activity [49], development of hyperphosphorylated tau [21] and neuronal apoptosis [41]. Aluminum is cholinotoxin [23]. It caused degeneration of cholinergic terminals in cortex and hippocampus [50]. In order to build a preliminary idea about the possible protective mechanism of memantine against aluminum-induced neurotoxicity, it is essential to understand the relationship between aluminum-induced neurotoxicity and glutamate, which is unfortunately, still unclear. On one side, it was found that aluminum increased glutamate release from astrocytes [51] and potentiated the increase in glutamate-induced intracellular calcium overload [52]. It enhanced the excitotoxic damage on rat hippocampal cells [53]. Rats injected with aluminum for 4 weeks showed significant increase in the level of glutamate in the many brain regions: cerebrum, thalamic area, midbrain-hippocampal region and cerebellum [54,55]. From previous data we may conclude that glutamate and its related excitotoxicity might act as a contributing factor in aluminum-induced neuronal dysfunction. On the other side, other studies did not match with this hypothesis. It had been shown that aluminum exposure was associated with increased glutamate uptake by astrocytes and increased conversion to glutamine [56,57]. Aluminum toxicity was found to be independent of calcium or glutamate receptor activation [58]. In another study, aluminum exposure in vitro was not associated with alteration in long term potentiation or glutamate release in rat hippocampal slices [59]. Aluminum also impaired the release of glutamate from transverse rat hippocampal neurons, a mechanism by which aluminum could induce impairment in learning and memory [60]. According to this hypothesis the use of NMDA receptor blockers would further impair glutamatergic transmission and add negative effect on memory, which is in contrast to our results. As this is a pure behavioral study, the dynamics of the protective effect of memantine against aluminum-induced behavioral deficit needs extensive biochemical and histological evaluation. But at least, this is the first study to demonstrate the potential protective effect of memantine against aluminum-induced neurotoxicity. The mechanism by which memantine could protect against aluminum-induced neurotoxicity and behavioral dysfunction might be explained by a variety of factors. Memantine partially normalize information processing in the hippocampus, and when it was given early during the development of the pathology, it conferred neuronal and cognitive protection while indirectly prevented pathological microglial activation [61]. Memantine protected the basal forebrain neurons releasing acetylcholine [62]. It reduced the oxidative damage to proteins in cortex and hippocampus [11] and improved attention and memory of beta amyloid-injected rats [63]. Memantine was able to preserve memory during neuroinflammation [13,61].
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
Memantine delayed the progression of symptoms in Alzheimer’s disease patients [1]. The blockade of NMDA receptormediated excitotoxicity can help preserve neuronal structure and function [64–66]. The most significant problem being that at doses that exerted neuroprotective effects, NMDA antagonists caused adverse side effects ranging from memory dysfunction and psychotic reactions in humans [67–69] to acute injury and/or death of neurons in animal brain [70–72]. Memantine is rapidly displaced from the NMDA receptor, which may avoid prolonged receptor blockade and the detrimental effects on learning and memory associated with prolonged blockade of the NMDA receptor [64]. In conclusion, our study showed that memantine could prevent the development of aluminum-induced cognitive deficit if used in appropriate doses, but the possible pharmacological and molecular mechanisms should be fully explored.
References [1] Bullock R. Efficacy and safety of memantine in moderate-to-severe Alzheimer disease: the evidence to date. Alzheimer Dis Assoc Disord 2006;20:23–9. [2] Danysz W, Parsons CG. The NMDA receptor antagonist memantine as a symptomatological and neuroprotective treatment for Alzheimer’s disease: preclinical evidence. Int J Geriatr Psychiatry 2003;18:S23–32. [3] Minkeviciene R, Banerjee P, Tanila H. Memantine improves spatial learning in a transgenic mouse model of Alzheimer’s disease. J Pharmacol Exp Ther 2004;311:677–82. [4] Van Dam D, De Deyn PP. Cognitive evaluation of disease-modifying efficacy of galantamine and memantine in the APP23 model. Eur Neuropsychopharmacol 2006;16:59–69. [5] Miguel-Hidalgo JJ, Alvarez XA, Cacabelos R, Quack G. Neuroprotection by memantine against neurodegeneration induced by beta-amyloid (1-40). Brain Res 2002;958:210–21. [6] Yamada K, Takayanagi M, Kamei H, Nagai T, Dohniwa M, Kobayashi K, et al. Effects of memantine and donepezil on amyloid beta-induced memory impairment in a delayed-matching to position task in rats. Behav Brain Res 2005;162:191–9. [7] Watanabe T, Iwasaki K, Takasaki K, Yamagata N, Fujino M, Nogami A, et al. Dynamin 1 depletion and memory deficits in rats treated with Abeta and cerebral ischemia. J Neurosci Res 2010;88:1908–17. [8] Kamat PK, Tota S, Saxena G, Shukla R, Nath C. Okadaic acid (ICV) induced memory impairment in rats: a suitable experimental model to test anti-dementia activity. Brain Res 2010;1309:66–74. [9] Misztal M, Frankiewicz T, Parsons CG, Danysz W. Learning deficits induced by chronic intraventricular infusion of quinolinic acid—protection by MK-801 and memantine. Eur J Pharmacol 1996;296:1–8. [10] Camarasa J, Rodrigo T, Pubill D, Escubedo E. Memantine is a useful drug to prevent the spatial and non-spatial memory deficits induced by methamphetamine in rats. Pharmacol Res 2010;62:450–6. [11] Pietá Dias C, Martins de Lima MN, Presti-Torres J, Dornelles A, Garcia VA, Siciliani Scalco F, et al. Memantine reduces oxidative damage and enhances long-term recognition memory in aged rats. Neuroscience 2007;146:1719–25. [12] Heim C, Sontag KH. Memantine prevents progressive functional neurodegeneration in rats. J Neural Transm Suppl 1995;46:117–30. [13] Rosi S, Vazdarjanova A, Ramirez-Amaya V, Worley PF, Barnes CA, Wenk GL. Memantine protects against LPS-induced neuroinflammation, restores behaviorally-induced gene expression and spatial learning in the rat. Neuroscience 2006;142:1303–15. [14] Andrási E, Páli N, Molnár Z, Kösel S. Brain aluminum, magnesium and phosphorus contents of control and Alzheimer-diseased patients. J Alzheimers Dis 2005;7:273–84. [15] Wills MR, Savory J. Water content of aluminum, dialysis dementia, and osteomalacia. Environ Health Perspect 1985;63:141–7. [16] Xu N, Majidi V, Markesbery WR, Ehmann WD. Brain aluminum in Alzheimer’s disease using an improved GFAAS method. Neurotoxicology 1992;13:735–43. [17] Gauthier E, Fortier I, Courchesne F, Pepin P, Mortimer J, Gauvreau D. Aluminum forms in drinking water and risk of Alzheimer’s disease. Environ Res 2000;84:234–46. [18] Lukiw WJ. Alzheimer’s disease and aluminium. In: Yasui M, Strong MJ, Ota K, Verity MA, editors. Mineral and metal neurotoxicology. New York: CRC Press; 1997. p. 113–26. [19] Schnabel J. Alzheimer’s disease: arthritis of the brain? New Sci 1992;138:22–6. [20] Smith MA, Sayre LM, Monnier VM, Perry G. Radical AGEing in Alzheimer’s disease. Trends Neurosci 1995;18:172–6. [21] Walton JR. An aluminum-based rat model for Alzheimer’s disease exhibits oxidative damage, inhibition of PP2A activity, hyperphosphorylated tau, and granulovacuolar degeneration. J Inorg Biochem 2007;101:1275–84. [22] Bilkei-Gorzó A. Neurotoxic effect of enteral aluminium. Food Chem Toxicol 1993;31:357–61. [23] Gulya K, Rakonczay Z, Kása P. Cholinotoxic effects of aluminium in rat brain. J Neurochem 1990;54:1020–6.
37
[24] Shuchang H, Qiao N, Piye N, Mingwei H, Xiaoshu S, Feng S, et al. Protective effects of gastrodia elata on aluminium-chloride-induced learning impairments and alterations of amino acid neurotransmitter release in adult rats. Restor Neurol Neurosci 2008;26:467–73. [25] Abdel-Aal RA, Assi AA, Kostandy BB. Rivastigmine reverses aluminum-induced behavioral changes in rats. Eur J Pharmacol 2011;659:169–76. [26] Creeley C, Wozniak DF, Labruyere J, Taylor GT, Olney JW. Low doses of memantine disrupt memory in adult rats. J Neurosci 2006;26:3923–32. [27] Van Dam D, Abramowski D, Staufenbiel M, De Deyn PP. Symptomatic effect of donepezil, rivastigmine, galantamine and memantine on cognitive deficits in the APP23 model. Psychopharmacology 2005;180:177–90. [28] Sukhanov IM, Zakharova ES, Danysz W, Bespalov AY. Effects of NMDA receptor channel blockers, MK-801 and memantine, on locomotor activity and tolerance to delay of reward in Wistar-Kyoto and spontaneously hypertensive rats. Behav Pharmacol 2004;15:263–71. [29] Réus GZ, Valvassori SS, Machado RA, Martins MR, Gavioli EC, Quevedo J. Acute treatment with low doses of memantine does not impair aversive, non-associative and recognition memory in rats. Naunyn Schmiedebergs Arch Pharmacol 2008;376:295–300. [30] Pitsikas N, Sakellaridis N. Memantine and recognition memory: possible facilitation of its behavioral effects by the nitric oxide (NO) donor molsidomine. Eur J Pharmacol 2007;571:174–9. [31] Yuedea CM, Dong H, Csernansky JG. Anti-dementia drugs and hippocampaldependent memory in rodents. Behav Pharmacol 2007;18:347–63. [32] Doody RS, Tariot PN, Pfeiffer E, Olin JT, Graham SM. Meta-analysis of six-month memantine trials in Alzheimer’s disease. Alzheimers Dement 2007;3:7–17. [33] Danysz W, Parsons CG, Kornhuber J, Schmidt WJ, Quack G. Aminoadamantanes as NMDA receptor antagonists and antiparkinsonian agents—preclinical studies. Neurosci Biobehav Rev 1997;21:455–68. [34] Danysz W, Essmann U, Bresink I, Wilke R. Glutamate antagonists have different effects on spontaneous locomotor activity in rats. Pharmacol Biochem Behav 1994;48:111–8. [35] Kos T, Popik P. A comparison of the predictive therapeutic and undesired side effects of the NMDA receptor antagonist, memantine, in mice. Behav Pharmacol 2005;16:155–61. [36] Zajaczkowski W, Quack G, Danysz W. Infusion of (+)-MK-801 and memantinecontrasting effects on radial maze learning in rats with entorhinal cortex lesion. Eur J Pharmacol 1996;296:239–46. [37] Réus GZ, Stringari RB, Kirsch TR, Fries GR, Kapczinski F, Roesler R, et al. Neurochemical and behavioural effects of acute and chronic memantine administration in rats: further support for NMDA as a new pharmacological target for the treatment of depression? Brain Res Bull 2010;81:585–9. [38] Garibova TL, Voronina TA, Litvinova SA, Kuznetsova AL, Kul’chikov AE, Alesenko AV. Features of memantine action profile in cholinergic deficit and intracerebral posttraumatic hematoma (hemorrhagic stroke) models in rats. Eksp Klin Farmakol 2008;71:8–13 [abstract]. [39] Nakamura S, Murayama N, Noshita T, Katsuragi R, Ohno T. Cognitive dysfunction induced by sequential injection of amyloid-beta and ibotenate into the bilateral hippocampus; protection by memantine and MK-801. Eur J Pharmacol 2006;548:115–22. [40] Kawahara M, Kato M, Kuroda Y. Effects of aluminum on the neurotoxicity of primary cultured neurons and on the aggregation of beta-amyloid protein. Brain Res Bull 2001;55:211–7. [41] Niu Q, Yang Y, Zhang Q, Niu P, He S, Di Gioacchino M, et al. The relationship between Bcl-gene expression and learning and memory impairment in chronic aluminum-exposed rats. Neurotox Res 2007;12:163–9. [42] Sun X, Liu Z, Zhang X, Zhang Z. Effects of aluminum on the number of neurons granulovacuolar degeneration in rats. Wei Sheng Yan Jiu 1999;28:164–6 [abstract]. [43] Connor DJ, Jope RS, Harrell LE. Chronic, oral aluminum administration to rats: cognition and cholinergic parameters. Pharmacol Biochem Behav 1988;31:467–74. [44] Flaten TP, Alfrey AC, Birchall JD, Savory J, Yokel RA. Status and future concerns of clinical and environmental aluminum toxicology. J Toxicol Environ Health 1996;48:527–41. [45] Schlatter C. Biomedical aspects of aluminium. Med Lav 1992;83:470–4. [46] Julka D, Vasishta RK, Gill KD. Distribution of aluminum in different regions and body organs of rat. Biol Trace Elem Res 1996;52:181–92. [47] Kaur A, Joshi K, Minz RM, Gill KD. Neurofilament phosphorylation and disruption: a possible mechanism of chronic aluminium toxicity in Wistar rats. Toxicology 2006;219:1–10. [48] Lal B, Gupta A, Gupta A, Murthy RC, Ali MM, Chandra SV. Aluminium ingestion alters behavior and some neurochemicals in rats. Indian J Exp Biol 1993;31:30–5. [49] Sethi P, Jyoti A, Singh R, Hussain E, Sharma D. Aluminium-induced electrophysiological, biochemical and cognitive modifications in the hippocampus of aging rats. Neurotoxicology 2008;29:1069–79. [50] Platt B, Fiddler G, Riedel G, Henderson Z. Aluminium toxicity in the rat brain: histochemical and immunocytochemical evidence. Brain Res Bull 2001;55:257–67. [51] Albrecht J, Simmons M, Dutton GR, Norenberg MD. Aluminum chloride stimulates the release of endogenous glutamate, taurine and adenosine from cultured rat cortical astrocytes. Neurosci Lett 1991;127:105–7. [52] Mundy WR, Freudenrich TM, Kodavanti PR. Aluminum potentiates glutamateinduced calcium accumulation and iron-induced oxygen free radical formation in primary neuronal cultures. Mol Chem Neuropathol 1997;32:41–57.
38
R.A. Abdel-Aal et al. / Behavioural Brain Research 225 (2011) 31–38
[53] Matyja E. Aluminum enhances glutamate-mediated neurotoxicity in organotypic cultures of rat hippocampus. Folia Neuropathol 2000;38:47–53. [54] El-Rahman SS. Neuropathology of aluminum toxicity in rats (glutamate and GABA impairment). Pharmacol Res 2003;47:189–94. [55] Nayak P, Chatterjee AK. Effects of aluminium exposure on brain glutamate and GABA systems: an experimental study in rats. Food Chem Toxicol 2001;39:1285–9. [56] Struys-Ponsar C, Guillard O, van den Bosch de Aguilar P. Effects of aluminum exposure on glutamate metabolism: a possible explanation for its toxicity. Exp Neurol 2000;163:157–64. [57] Zielke HR, Jackson MJ, Tildon JT, Max SR. A glutamatergic mechanism for aluminum toxicity in astrocytes. Mol Chem Neuropathol 1993;19:219–33. [58] Brenner SR, Yoon KW. Aluminum toxicity in rat hippocampal neurons. Neurosci Lett 1994;178:260–2. [59] Gilbert ME, Shafer TJ. In vitro exposure to aluminum does not alter long-term potentiation or glutamate release in rat hippocampal slices. Neurotoxicol Teratol 1996;18:175–80. [60] Provan SD, Yokel RA. Aluminum inhibits glutamate release from transverse rat hippocampal slices: role of G proteins, Ca channels and protein kinase C. Neurotoxicology 1992;13:413–20. [61] Rosi S, Ramirez-Amaya V, Vazdarjanova A, Esparza EE, Larkin PB, Fike JR, et al. Accuracy of hippocampal network activity is disrupted by neuroinflammation: rescue by memantine. Brain 2009;132:2464–77. [62] Wenk GL, Zajaczkowski W, Danysz W. Neuroprotection of acetylcholinergic basal forebrain neurons by memantine and neurokinin B. Behav Brain Res 1997;83:129–33. [63] Nyakas C, Granic I, Halmy LG, Banerjee P, Luiten PG. The basal forebrain cholinergic system in ageing and dementia, rescuing cholinergic neurons from neurotoxic amyloid-beta42 with memantine. Behav Brain Res 2010;221:594–603.
[64] Lipton SA. Paradigm shift in neuroprotection by NMDA receptor blockade: memantine and beyond. Nat Rev Drug Discov 2006;5:160–70. [65] Lipton SA. Pathologically-activated therapeutics for neuroprotection: mechanism of NMDA receptor block by memantine and S-nitrosylation. Curr Drug Targets 2007;8:621–32. [66] Wenk GL, Parsons CG, Danysz W. Potential role of N-methyl-d-aspartate receptors as executors of neurodegeneration resulting from diverse insults: focus on memantine. Behav Pharmacol 2006;17:411–24. [67] Grotta J, Clark W, Coull B, Pettigrew LC, Mackay B, Goldstein LB, et al. Safety and tolerability of the glutamate antagonist CGS 19755 (Selfotel) in patients with acute ischemic stroke. Results of a phase IIa randomized trial. Stroke 1995;26:602–5. [68] Herrling PL. D-CPPene (SDZ EAA 494), a competitive NMDA antagonist: results from animal models and first results in humans. Neuropsychopharmacology 1994;10:591S. [69] Krystal JH, Karper LP, Seibyl JP, Freeman GK, Delaney R, Bremner JD, et al. Subanesthetic effects of the noncompetitive NMDA antagonist, ketamine, in humans. Psychotomimetic, perceptual, cognitive, and neuroendocrine responses. Arch Gen Psychiatry 1994;51:199–214. [70] Fix AS, Horn JW, Wightman KA, Johnson CA, Long GG, Storts RW, et al. Neuronal vacuolization and necrosis induced by the noncompetitive N-methylD-aspartate (NMDA) antagonist MK(+)801 (dizocilpine maleate): a light and electron microscopic evaluation of the rat retrosplenial cortex. Exp Neurol 1993;123:204–15. [71] Olney JW, Labruyere J, Wang G, Wozniak DF, Price MT, Sesma MA. NMDA antagonist neurotoxicity: mechanism and prevention. Science 1991;254:1515–8. [72] Wozniak DF, Dikranian K, Ishimaru MJ, Nardi A, Corso TD, Tenkova T, et al. Disseminated corticolimbic neuronal degeneration induced in rat brain by MK801: potential relevance to Alzheimer’s disease. Neurobiol Dis 1998;5:305–22.