Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment

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Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment Shuang Shaoa, Man Lia, Wei Dua, Feng Shaoa,1, Weiwen Wangb,2 a

Department of Psychology, Peking University, Beijing 100871, China Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing 100101, China

b

art i cle i nfo

ab st rac t

Article history:

Adolescence is a critical period for neurodevelopment. MK-801 treatment and social

Accepted 12 September 2014

isolation are important animal models for various neurodevelopmental disorders. Dysfunctions in the central cholinergic system are involved in creating the cognitive deficits

Keywords:

observed in neurological diseases. In the present study, we aimed to investigate whether

Adolescence

the acetylcholinesterase inhibitor galanthamine could reverse pre-cognitive prepulse

MK-801

inhibition (PPI) deficits and spatial learning deficits of adult rats in the Morris water maze.

Social isolation

We induced these effects using either adolescent MK-801 treatment or social isolation from

Galanthamine

postnatal day (PND) 38–51. Our results showed that both adolescent social isolation and

Prepulse inhibition

MK-801 treatment impaired PPI in adult rats, but neither had an effect on spatial learning. Furthermore, galanthamine injections over 7 days significantly enhanced PPI of normal rats and improved PPI disruption induced by adolescent pharmacological and rearing interventions. The results suggest that acetylcholinesterase inhibitors, such as galanthamine, might have the potential to improve pre-cognition in neurodevelopmental diseases by improving auditory sensory gating. & 2014 Elsevier B.V. All rights reserved.

1.

Introduction

The cholinergic system is involved in learning and synaptic plasticity (André et al., 2011). Dysfunctions in the central cholinergic system or the degeneration of cholinergic cells are involved in the cognitive deficits that characterize a wide range of neurological disorders, including Alzheimer’s disease, Parkinson’s disease, and schizophrenia (André et al.,

2011; Barak, 2009; Ellenbroek, 2012). It has been demonstrated that cholinergic dysfunction is associated with the pathology of the memory and cognitive impairments observed in schizophrenia patients (Tracy et al., 2001). Recently, several reviews have indicated that therapy with muscarinic agonists and nicotinic agonists results in an improvement in positive symptoms as well as in cognitive function (Dome et al., 2010; Langmead et al., 2008; Raedler, 2008).

E-mail addresses: [email protected] (F. Shao), [email protected] (W. Wang). Department of Psychology, Peking University, 5 Yiheyuan Road, Beijing 100871, China. Fax: þ86 10 62761081. 2 Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, 4A Datun Road, Beijing 100101, China. Fax: þ86 10 64872070. 1

http://dx.doi.org/10.1016/j.brainres.2014.09.032 0006-8993/& 2014 Elsevier B.V. All rights reserved.

Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032

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The relationship between the cholinergic system and precognitive or cognitive function has also been demonstrated in animal experiments. For example, α7 neuronal nicotinic receptor agonists, such as TC-5619, might have potential effects on schizophrenia-like mouse models of pre-cognitive prepulse inhibition (PPI) dysfunction and on models of positive and negative symptoms (Hauser et al., 2009). A sustained depletion of cholinergic neurons in the Nucleus Accumbens (NAc) of rats induced a reduction in the PPI of the acoustic startle response (Laplante et al., 2011). PPI is thought to reflect sensorimotor gating mechanisms, and it is impaired in patients who suffer from schizophrenia (Li et al., 2009; Marsden et al., 2011). Experimental evidence in animal models of schizophrenia has demonstrated that the forebrain cholinergic system mediates cognitive symptoms such as attentional performance (Sarter et al., 2012). Non-competitive N-methyl-D-aspartate (NMDA) glutamate receptor antagonists such as dizocilpine (MK-801) produce PPI deficits in humans and animals (Gururajan et al., 2010; Oh et al., 2013; Pietraszek et al., 2005). Rearing rodents in social isolation from weaning to adulthood produces consistent, long-lasting pre-cognitive deficits related to neuropsychological disorders, including PPI and latent inhibition (LI) (Fone and Porkess, 2008). Several studies have indicated that adolescent environmental disturbances produce profound behavioral and neurochemical changes in adult rats (Adrian and Laviola., 2004; Laviola and Marco., 2011; Lukkes et al., 2009a,b; Marco et al., 2011; McCormick et al., 2008). Previous studies in our laboratory have found that adolescent social isolation impaired LI and reversal learning in adult rats (Han et al., 2012, 2011; Shao et al., 2009). Galanthamine is an alkaloid that inhibits acetylcholinesterase activity, augments central cholinergic transmission, and is commonly used to treat memory impairments in patients with Alzheimer’s disease (Harvey, 1995). Recent human studies have reported that acetylcholinesterase inhibitors may have a therapeutic role for memory dysfunction in schizophrenic patients (Gustavson and Cummings, 2003; Postma et al., 2006; Terry et al., 2005). It has also been demonstrated that acetylcholinesterase inhibitors may enhance PPI in rats (Hohnadel et al., 2007). In the current study, we wanted to determine whether long-term galanthamine injections had the potential to improve the PPI deficiencies induced by MK-801 and social isolation. In this study, we first investigated the effects of MK801 injections and social isolation during adolescence (from PND 38–51) on the function of PPI and spatial learning in the Morris water maze test of male Wistar rats. We then observed whether long-term galanthamine injections (from PND 56–62) could improve deficits in PPI and spatial learning.

Fig. 1 – PPI performance of adult rats individually housed during adolescence (n ¼ 6 per group, *** denotes po.001).

isolated-saline group was significantly decreased. This reflects the PPI deficiency induced by isolated rearing in adolescence (F(1,10)¼5.16, po0.001). In addition, there was a significant effect of galanthamine injections (F(1,20)¼82.10, po0.001). The PPI of the social-galanthamine group was significantly higher than in the social-saline group (F(1,10)¼ 7.27, po0.001). The PPI of the isolated-galanthamine group was also significantly higher compared to the isolated-saline group (F(1,10)¼5.55, po0.001). However, there was no significant difference between the PPI of the isolated-galanthamine and the social-saline rat groups, which suggests that galanthamine can increase the PPI of normal rats and improve the PPI deficiency induced by adolescent isolated rearing.

2.1.2. The effects of galanthamine on the spatial learning of isolated rats The average escape latency during spatial learning showed that the effects of rearing conditions and galanthamine injections were not significant (F(1,20)¼0.09, p¼ 0.77; F(1,20)¼0.89, p¼ 0.36). The effect of the test day was significant (F(3,30)¼56.24, po0.001), which reflected an overall cumulative learning process. The interactions between rearing conditions, galanthamine injections and the test day were not significant. The average distance traveled during spatial learning analysis revealed no significant main effects of rearing conditions (F(1,20)¼ 0.06, p¼ 0.80) or galanthamine injections (F(1,20)¼ 2.04, p ¼0.16), and no significant interaction between rearing conditions, galanthamine and the test day was found. This result was similar to the escape latency results. In contrast, the effect of the test day was significant (F(3,30)¼55.21, po0.001). When combined with the escape latency data, these results indicate that isolated rearing and galanthamine injections did not affect spatial learning ability.

2.2.

2.

Results

2.1.

Experiment 1

2.1.1.

The effects of galanthamine on the PPI of isolated rats

The PPI for each group is shown in Fig. 1. There was a significant main effect of rearing conditions (F(1,20)¼ 96.04, po0.001). Further analysis revealed that compared with the rats in the social-saline group, the PPI of the rats in the

Experiment 2

2.2.1. The effects of galanthamine on the PPI of MK-801injected rats The PPI for the four groups is shown in Fig. 2. The results showed that there was a significant main effect of MK-801 injections (F(1,20)¼ 190.06, po0.001) and galanthamine injections (F(1,20)¼ 186.99, po0.001). The interaction between MK801 and galanthamine was also significant (F(1,20)¼25.23, po0.001). Further analysis revealed that the PPI of the rats in

Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032

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Fig. 2 – PPI performance of adult rats injected with MK-801 during adolescence (n ¼6 per group, *** denotes po.001).

the MK-801-saline group was decreased significantly compared to the rats in the saline-saline group (F(1,10)¼ 14.69 po0.001). The PPI of the saline-galanthamine group was significantly increased compared to the saline-saline group (F(1,10)¼ 6.97, po0.001); compared with the rats in the MK-801-saline group, the PPI of the MK-801-galanthamine group significantly increased. (F(1,10)¼ 11.93, po0.001). However, there was no significant difference between the PPI of the rats in the MK-801-galanthamine and saline-saline groups. These results indicate that adolescent MK-801 injections induced PPI deficiency, galanthamine increased PPI, and, most importantly, galanthamine can improve the PPI impairment induced by adolescent MK-801 injections.

2.3. The effects of galanthamine on the spatial learning of MK-801 treated rats The average escape latency for the rats in the four groups during spatial learning is summarized in Fig. 3A. There were no significant main effects of MK-801 treatment and galanthamine injections, but the effect of the test day was significant (F(3,30)¼ 45.28, po0.001), which is similar to the results of experiment 1. The interactions between rearing conditions, galanthamine injections, and the test day were not significant. The distance is summarized in Fig. 3B. The main effects of galanthamine injections and MK-801 treatment were not significant, but the effect of the test day was significant (F(3,96)¼ 43.505, po0.001). The interactions between galanthamine injections and MK-801 treatment were also significant (F(1,32)¼ 9.420, po0.005). The posthoc test analysis indicated that compared to the rats in the MK801-saline group, the MK-801galanthamine rats traveled a significantly shorter distance (po0.003). Further analysis indicated that the significant difference was present on the first day (po0.01), and there was no significant difference between the saline–saline and salinegalanthamine groups or the saline–saline and MK-801-saline groups. Together, these results indicate that adolescent MK-801 treatment did not affect spatial learning in the Morris water maze, but galanthamine treatment could partially enhance the spatial learning ability of MK-801 injected rats.

3.

Discussion

In the current study, we found that MK-801 treatment and social isolation during adolescence (PND 38–51) induced PPI

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impairment in adult rats. This PPI impairment could be improved by galanthamine injections for 7 days. Galanthamine also increased the PPI of normal rats. However, spatial learning in the Morris water maze was not affected by adolescent MK-801 treatment and isolated rearing, and galanthamine could partially enhance the spatial learning ability of MK-801 injected rats. Previous studies have shown that both MK-801 treatment and isolated rearing disrupt PPI in adult rats. PPI disruption produced by MK-801 has been demonstrated in rats and mice (Curzon and Decker, 1998; Dean et al., 2010; Gururajan et al., 2010; Oh et al., 2013). In these studies, MK-801 was administered via a single injection 15 min (Curzon and Decker, 1998; Dean et al., 2010), 20 min (Gururajan et al., 2010), or 30 min (Oh et al., 2013) prior to PPI testing in adults. Several studies from Koch’s group have also revealed that acute MK-801 injections (10 min prior to PPI testing) (Schwabe and Koch, 2004), sub-chronic MK-801 treatment (for 11 days) (Schwabe et al., 2005) or stimulation of the ventral hippocampus with NMDA (Klarner et al., 1998) induced long-lasting PPI disruption of rats. Several previous studies have shown that a single MK-801 injection during adolescence can induce changes in motor activity (Pešića et al., 2010), social approach deficits (Moy et al., 2013), impaired consolidation and reconsolidation of passive avoidance conditioning (Flint et al., 2013) in adolescent animals. Furthermore, a recent study reported that a single injection per day of MK-801 (0.2 mg/kg) for 14 days during adolescence disrupted the spatial working memory in the Morris water maze in adolescent and young adult rats (Li et al., 2011). However, our study is the first to indicate that chronic treatment of MK-801 for 14 days during adolescence produced PPI impairment in adult rats. It has been demonstrated that isolation-reared mice and rats show a robust reduction in the PPI of acoustic startle (Fone and Porkess, 2008; Heidbreder et al., 2000; Weiss et al., 2001). In most of the previous studies, isolated rearing was conducted from weaning to adulthood. Several recent studies focused on the effects of adolescent social isolation indicated that brief isolation rearing during adolescence can also disrupt adult rat behaviors, including increased anxiety and conditioned fear behaviors (Lukkes et al., 2009a,b; McCormick et al., 2008), reduced social activity (Hol et al., 1999), and impaired spatial memory performance (McCormick et al., 2010). Recent studies from our group have shown that brief isolated rearing during adolescence can also disrupt cognitive, emotional and locomotor behaviors of adult rats (Han et al., 2012, 2011; Meng et al., 2010; Shao et al., 2009). However, the current data are the first to demonstrate that adolescent social isolation from PND 38 to 51 impaired PPI in adult rats. Spatial learning in the Morris water maze was not affected by adolescent MK-801 treatment and isolated rearing in the present study. In contrast, as we have mentioned previously, another study has reported that MK-801 injections over 14 days during adolescence (PND 28–41) disrupted the spatial working memory in the Morris water maze in adolescent (PND 42) and young adult SD rats (PND 56) (Li et al., 2011). This discrepancy may be due to the different rat species, the time window at which the MK-801 treatment and cognitive measurement were applied, and the different methods for testing

Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032

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Fig. 3 – Spatial learning performance of adult rats injected with MK-801 during adolescence: latency to escape (A) and distance traveled to escape (B). The results are expressed as the means7S.E.M. (n ¼ 6 per group, ** denotes po.001, MK-801-saline and MK-801-galanthamine groups).

cognitive function in MWM. Further experiments are needed to investigate the effects of adolescent MK-801 treatment on the cognitive function of rats. Two previous studies from our group have also found that early social isolation (PND 21–34) did not impair spatial learning in the Morris water maze (Han et al., 2011), but it did disrupt LI in adult rats (Han et al., 2012). It is well known that PPI is a useful index of sensorimotor gating mechanisms and may reflect overload-induced cognitive fragmentation. LI represents the interaction of associative and non-associative learning for a specific stimulus, thereby modeling an attentional process. Impairments in PPI and LI have often been reported in patients with schizophrenia and other psychiatric disorders (Braff et al., 2001; Fone and Porkess, 2008; Keeler and Robbins, 2011; Weiner and Arad, 2009). Taken together, the current data and previous results from our group suggest that adolescent social isolation or NMDA receptor antagonist treatment can be used as an animal model of schizophrenia. The current finding also demonstrates that galanthamine can enhance PPI in normal rats and spatial learning in the Morris water maze of MK-801 injected rats, which is consistent with the previous studies. As a central-type acetylcholinesterase inhibitor, galanthamine can raise the level of the neurotransmitter acetylcholine (Bajgar et al., 2007) and upregulate nicotinic receptors in cortical neurons (Kume et al., 2005) to augment cognitive functions. More importantly, our present results revealed that after 7 days of galanthamine injections, the PPI of the MK-801galanthamine and isolation-galanthamine rats was significantly improved. This suggests that PPI deficiency in adult rats induced by adolescent isolation and MK-801 treatment can be enhanced by 7 days of galanthamine injections. Several previous studies have suggested that acetylcholinesterase inhibitors could be therapeutic for schizophrenia by improving PPI and cognitive function. For example, an animal study reported that galanthamine could improve PPI deficits in all three pharmacological models, including the dopamine receptor agonist apomorphine, the NMDA receptor antagonist MK801 and the muscarinic acetylcholine receptor antagonist scopolamine (Hohnadel et al., 2007). A previous clinical study indicated that galanthamine improves short-term memory and attention in schizophrenic patients (Schubert et al., 2006). Disruption of PPI, a well-characterized model of sensory information-processing deficits, has been clearly investigated in schizophrenic patients (Braff et al., 2001). It has recently been

shown that intra-accumbens cholinergic neurotransmission plays a particularly important role in sensorimotor gating. An impaired balance between striatal dopamine and acetylcholine activities may be related to the pathophysiology of schizophrenia (Laplante et al., 2011). However, the PPI enhancement caused by galanthamine in this study requires further investigation. It has been well established that both cholinergic and glutamatergic systems are involved in learning and memory, and there is some evidence that suggests the interaction between cholinergic and glutamatergic systems is an important factor in the regulation of some forms of cognitive processes (Aigner, 1995). For example, behavioral pharmacological studies have identified that the coadministration of MK-801 and a nonselective muscarinic receptor antagonist in small doses disrupts the performance of animals in the inhibitory avoidance task (Mahmoodi et al., 2010; Moreira et al., 2005) and the fear conditioning task (Figueredo et al., 2008). It has also been demonstrated that the administration of acetylcholine facilitates the “slow” component of the excitatory post-synaptic potential (EPSP) mediated by NMDA-receptor activation. This suggests that modulatory cholinergic functions are involved in synaptic plasticity, such as NMDA-dependent long-term potentiation (LTP) (Auerbach and Segal., 1994; Markram and Segal, 1990). The beneficial effects of galanthamine on PPI disruption induced by MK-801 may be related to the complex cholinergic-glutamatergic interactions. Further studies are required to determine the detailed underlying mechanisms. In conclusion, the present data indicated that adolescent social isolation or MK-801 treatment induced PPI deficits in adult rats, but did not affect spatial learning. Galanthamine injections over 7 days significantly increased PPI of normal rats and improved PPI disruption induced by adolescent MK-801 treatment and social isolation. These results suggest that some acetylcholinesterase inhibitors, such as galanthamine, might have the potential to improve pre-cognition in schizophrenia by improving auditory sensory gating.

4.

Experimental procedures

4.1.

Animals

Ninety-six male Wistar rats were obtained from the Academy of Chinese Military Medical Science (Beijing, China) on post-natal

Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032

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day (PND) 21. The rats were maintained under standard conditions (ambient temperature 22 1C, 12 h light/dark cycle, light on at 7:00 a.m.) with ad libitum access to food and water. The experiments were performed in accordance with the guidelines of the Beijing Laboratory Animal Center and the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publications No. 80-23).

4.2.

Drugs

All drugs were dissolved in vehicle (0.9% saline) and administered in a volume of 1.0 ml/kg. MK-801 (Sigma, USA) 0.2 mg/kg i.p. (Li et al., 2011) was administered from PND 38–51 (Shao et al., 2009) for rats in the MK-801-saline and MK-801galanthamine groups. Galanthamine (Sigma, USA) 0.5 mg/kg i.p. (Dimitrova and Getova, 2002, 2003) was injected from PND 56–62 (rats older than PND 56 can be considered early adulthood; Lukkes et al., 2009b) for rats in the MK-801galanthamine, saline-galanthamine, social-galanthamine and isolated-galanthamine groups.

4.3.

Experimental design

4.3.1.

Experiment 1

On PND 38, 48 rats were randomly assigned to four groups (12 rats per group). In the social-saline group, the rats were socially reared with 4 rats per cage (500 mm  360 mm  250 mm) from PND 38–51 and injected with saline from PND 56–62. In the social-galanthamine group, the rats were socially reared and injected with galanthamine. In the isolated-saline group, the rats were reared in isolation with 1 rat per cage (500 mm  360 mm  250 mm) from PND 38–51 and injected with saline from PND 56–62. In the isolatedgalanthamine group, the rats were reared in isolation and injected with galanthamine. After isolation, the isolated rats were randomly assigned to and placed in a rearing group. Socially reared rats were randomly reassigned to a new group to ensure that any difference observed between the isolationreared and socially reared rats was not because of the re-socialization procedure. At the end of the procedure, PPI and spatial learning in the Morris water maze were tested in half of the rats (n ¼6) in each group.

4.3.2.

Experiment 2

On PND 38, 48 rats were randomly assigned to four groups (12 rats per group). In the MK-801-saline group, the rats were given MK-801 from PND 38–51 and saline from PND 56–62. In the MK-801-galanthamine group, the rats were injected with MK-801 and galanthamine. In the saline–saline group, the rats were given saline. In the saline-galanthamine group, the rats were injected with saline and galanthamine. At the end of the procedure, PPI and spatial learning in the Morris water maze were tested in half of the rats (n¼ 6) in each group. The timeline of the experimental design is summarized in Fig. 4.

4.4.

Behavioral test

4.4.1.

PPI test

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On PND 63, PPI was measured using the Coulbourn Instruments Acoustic Response Test System (Coulbourn Instruments, Allentown, PA, USA), which consisted of one weight-sensitive platform inside of a single sound-attenuated chamber (Li et al., 2013). An interfaced computer recorded the maximum response that occurred within 200 ms of the onset of the startle-eliciting stimulus. A 5-min adaptation period occurred in which no startle stimuli were presented. The decibel levels were verified using a Larson–Davis Sound Pressure Machine Model 2800 (Provo, UT, USA). Each stimulus had a 2-ms rise and decay time to ensure that the onset and offset were abrupt, which is a primary criterion for a startle. There were two types of stimulus trials, and each trial type was presented 20 times. The trial types were presented in a random order to avoid order effects and habituation. The inter-trial intervals randomly ranged from 10 to 20 s. The trial types included 1) a 120 dB pulse alone and 2) a 120 dB stimulus preceded by a 77 dB prepulse. The pulse stimuli lasted for 40 ms, and the prepulse stimuli lasted for 20 ms. A ventilating fan provided an ambient noise level of 65 dB throughout the entire testing period to mask the effects of noises from outside of the sound-attenuating chamber. After each observation, the cage was cleaned with ethyl alcohol (10%) to remove remaining olfactory cues from the previous subject. The percentage of PPI induced by each prepulse intensity was calculated as follows: [100 (100  startle amplitude in the prepulse trial)/(startle amplitude in the pulse alone trial)].

4.4.2. Spatial learning in Morris water maze 4.4.2.1. Apparatus. Testing was conducted in a circular pool 150 cm in diameter, with water that was 22 cm deep (2372 1C). A circular Plexiglas platform (8 cm diameter) was placed 2 cm beneath the water level at different locations, depending on which test was employed. The water was made cloudy by adding milk. Distinctive visual cues were placed on the wall surrounding the pool, and a video camera was positioned above the water maze. The swim paths of the rats were tracked, digitized and stored for later behavioral analysis using Ethovision 3.1 (Noldus). The water maze was divided into four logical quadrants (north, south, east and west) that served as starting positions for the rats. All animals were tested in the spatial learning of the Morris water maze (Han et al., 2011).

4.4.2.2. Spatial learning. The spatial learning task consisted of 4 days of acquisition with the hidden platform, followed by a probe test without the platform on the fifth day. The platform was fixed in the middle of the west quadrant

Fig. 4 – The timeline of the experiment.

Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032

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45 cm from the maze wall. During the first 4 days, four swim trials were conducted per day in which each animal was released from a different quadrant in each trial. This process was performed in a pseudo-random manner, and the start quadrant varied for each day. A maximum of 60 s was allowed for each trial. If the rat did not find the platform within 60 s, it was guided to the platform and allowed to remain there for 10 s. At the end of the daily session, the rats were dried with paper towels and returned to their home cages. We recorded both the latency to escape onto the platform and the distance traveled.

4.5.

Statistical analyses

The data are presented as the means7standard error of the mean (SEM) for all measures. The analysis was performed using SPSS 16 software (SPSS Inc., China). Group differences in the PPI data were analyzed using a 2  2 ANOVA that consisted of two between-subjects main factors. These factors included the rearing conditions and galanthamine injections for experiment 1 and the MK-801 and galanthamine injections for experiment 2. The Morris water maze results were analyzed using three-way repeated measures analysis of variance (ANOVA) with rearing conditions and drug injections as the independent factors and test day as the withinsubject factor. Following significant analyses of variance, LSD was used as the post-hoc test for the between-subject factor, and Bonferroni correction was used as the post-hoc test for the within-subject factor. A probability level of po0.05 was considered statistically significant.

Acknowledgments This work was supported by the National Natural Science Foundation of China (Grant no. 31070910), the National Natural Science Foundation of China (Grant no. 91132728), the Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2-EW-J-8) and the Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences.

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Please cite this article as: Shao, S., et al., Galanthamine, an acetylcholine inhibitor, prevents prepulse inhibition deficits induced by adolescent social isolation or MK-801 treatment. Brain Research (2014), http://dx.doi.org/10.1016/j. brainres.2014.09.032