- Email: [email protected]
(+)-MK-801 induced social withdrawal in rats; a model for negative symptoms of schizophrenia
Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832 www.elsevier.com/locate/pnpbp
(+)-MK-801 induced social withdrawal in rats; a model for negative symptoms of schizophrenia Johan P. Runga,T, Arvid Carlssona, Katarina Ryde´n Markinhuhtab, Maria L. Carlssona a
The Arvid Carlsson Institute for Neuroscience, Institute of Clinical Neuroscience, The Sahlgrenska Academy, Go¨teborg University, Medicinaregatan 11, SE-405 30 Go¨teborg, Sweden b A Carlsson Research AB, Biotech Center, Arvid Wallgrens Backe 20, SE-413 46 Go¨teborg, Sweden Accepted 1 March 2005 Available online 23 May 2005
Abstract Dopaminergic agonists and NMDA-receptor antagonists form the basis for the dopamine and glutamate models of schizophrenia, respectively. In human subjects dopaminergic agonists evoke a psychosis resembling positive symptoms of schizophrenia, while NMDAreceptor antagonists produce both positive and negative symptoms. Consequently, the glutamate model may be considered the most complete of the two models. Alterations in animal behaviour, in response to amphetamine or NMDA-receptor antagonists, are widely used to model schizophrenia. NMDA-receptor antagonist induced social withdrawal in rat is an established model for negative symptoms of schizophrenia. In this study we have set up an automated method, based on video tracking, to assess social behaviour, motor activity and movement pattern in rats. This method was then used to evaluate the effects of amphetamine and the NMDA-receptor antagonist (+)-MK-801, administered as single intraperitoneal injections, on rat behaviour. Amphetamine caused significantly increased motor activity and a tendency towards stimulation of social interactions. (+)-MK-801 also stimulated motor activity, but induced a significant inhibition of social interactions. These results indicate that a single injection of (+)-MK-801 to rats models both positive and negative symptoms of schizophrenia. Amphetamine, in contrast, reflects only the positive symptoms of schizophrenia in this model. D 2005 Elsevier Inc. All rights reserved. Keywords: Amphetamine; (+)-MK-801; Negative symptoms; Rat; Schizophrenia; Social withdrawal; Video tracking
1. Introduction
1.2. Amphetamine psychosis and the dopamine hypothesis for schizophrenia
1.1. Models for schizophrenia The two main models or hypotheses for schizophrenia are the dopamine and the glutamate hypotheses for this disorder. The hyperdopaminergia model prevailed until the late 1980s when the glutamate model started to gain ground. Abbreviations: D2-receptor, dopaminergic D2-receptor; NMDA, N-methyl-d-aspartate; PCP, phencyclidine. * Corresponding author. The Arvid Carlsson Institute for Neuroscience, Institute of Clinical Neuroscience, The Sahlgrenska Academy, Go¨teborg University, Box 432, SE-405 30 Go¨teborg, Sweden. Tel.: +46 31 773 33 28; fax: +46 31 773 34 01. E-mail address: [email protected] (J.P. Rung). 0278-5846/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2005.03.004
Prolonged high dose self-administration, and occasionally even a single injection of amphetamine, are known to cause a psychosis typically characterized by paranoid delusions and hallucinations (Kokkinidis and Anisman, 1981; Young and Scoville, 1938), thus displaying resemblance to positive symptoms of schizophrenia (Beamish and Kiloh, 1960). This phenomenon has also been studied extensively under controlled conditions in the clinic with known doses (Angrist et al., 1974b). In individuals predisposed for developing schizophrenia even small doses of amphetamine may induce psychosis (West, 1974). On the other hand, low doses of amphetamine generally have beneficial effects on performance, attention, mood, social
828
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
abilities and results in intelligence tests (Weiner, 1964). There are no convincing reports of dopaminergic stimulators inducing behavioural or mental aberrations resembling negative symptoms of schizophrenia. Amphetamine has even been suggested to have a mitigating effect on negative symptoms in some schizophrenics (Sanfilipo et al., 1996; Van Kammen and Boronow, 1988). Amphetamines augment dopaminergic and noradrenergic neurotransmission by inducing catecholamine release and preventing catecholamine reuptake. Although the effect is not specific for dopamine, the prevailing view is that dopaminergic mechanisms underlie amphetamine psychosis. Furthermore, virtually all currently used antipsychotic agents suppress dopaminergic neurotransmission. Reports of at least some of these drugs alleviating symptoms of amphetamine psychosis (Angrist et al., 1974a; Jha and Fourie, 1999; Misra and Kofoed, 1997) provide support for both the dopamine hypothesis and the amphetamine model for schizophrenia. The dopamine hypothesis is further supported by the fact that patients suffering from Parkinson’s disease (PD) are known to develop paranoid delusions and hallucinations, mainly visual, following sustained (> 1 year) lDOPA treatment (Goetz et al., 1998; Klawans, 1988). It has been reported that PD patients with latent psychotic illness may experience hallucinations much sooner (< 3 months) after onset of l-DOPA treatment (Goetz et al., 1998).
receptor antagonists, MK-801 is by far the most potent (Lodge et al., 1994).
1.3. The phencyclidine or glutamate model for schizophrenia
1.5. Animal models for schizophrenia
The first and most striking support for the glutamate or phencyclidine model for schizophrenia is provided by the observation that phencyclidine (PCP) induces a psychotic state that includes both positive and negative symptoms in healthy individuals (Luby et al., 1959; Snyder, 1980). It should be recalled in this context, however, that the glutamate receptor blocking properties of PCP were not disclosed until 1982 (Lodge and Anis, 1982). Later, psychotomimetic effects were demonstrated with ketamine as well (Tamminga, 1999). Interestingly, Tamminga et al. (Lahti et al., 1995, 2001; Tamminga, 1999) found that schizophrenic patients exposed to ketamine experienced worsening or reappearance of positive symptoms characteristic of their individual psychoses. Surprisingly, these patients did not experience worsening of negative symptoms. This was hypothesized to be due to the high baseline in these individuals, with respect to negative symptoms, leading to a ceiling effect. PCP, ketamine and the hitherto not mentioned substance (+)-MK-801 (MK-801) all belong to a group of noncompetitive antagonists acting at the glutamatergic Nmethyl-d-aspartate (NMDA)-receptor complex, binding to a site located within the ion channel and blocking cation flow. Due to the location of the binding site, the ion channel needs to be open for these antagonists to bind, thus making the antagonism agonist dependent. Among these NMDA-
1.4. Advantage of the glutamate model Psychosis resulting from dopaminergic stimulation indeed shares many similarities with positive symptoms of schizophrenia, but does not include any characteristics that match negative symptoms. Furthermore, classic neuroleptics with pronounced dopamine D2-receptor blockade do not, in general, alleviate the negative symptoms in schizophrenic patients (see Blin, 1999). Taken together, these observations indicate that hyperdopaminergia is not directly responsible for negative symptoms in schizophrenia. In contrast, as mentioned above, dopamine agonists have been used successfully to treat negative symptoms. NMDA-receptor antagonists on the other hand produce a psychotic state that includes both negative and positive symptoms. Furthermore, at least l-DOPA induced psychosis typically involves visual hallucinations, whereas NMDAreceptor antagonists reportedly cause auditory hallucinations (Allen and Young, 1978). The hallucinations in schizophrenia are considered to be mainly auditory, often consisting of inner voices. Thus, we may conclude that NMDA-receptor antagonists provide a more complete model for schizophrenia than do dopaminergic agonists.
NMDA-receptor antagonists and dopaminergic agonists administered to mammals constitute two widely used animal models for schizophrenia. Behavioural studies performed in rodents treated with these substances reveal behaviours that correspond to different symptoms of schizophrenia. The perhaps most studied behavioural aspect is motor activity. Drug induced hyperactivity in rodents may correspond to positive symptoms of schizophrenia (Nilsson et al., 2004; Sams-Dodd et al., 1997). Cognitive deficits may be modelled with memory and learning tasks (Arnt, 1998). Social withdrawal is a core negative symptom in schizophrenia and may be modelled by various drug treatments in animals (Sams-Dodd et al., 1997). The prevailing view seems to be that unlike NMDA-receptor antagonists amphetamine does not induce social withdrawal (Sams-Dodd, 1995a, 1998b), although there are reports of amphetamine hampering social behaviour in non-human primates (Castner et al., 2004). However, this latter finding does not tally with observations in human subjects. It should be mentioned in this context that social withdrawal in rodents is also used for modelling anxiety (File, 1980; File and Seth, 2003). However, in the literature NMDA-receptor antagonists are described as being both anxiolytic (Wieronska et al., 2003) and anxiogenic (File and Seth, 2003). Furthermore, the anxiolytic drug diazepam does not seem to reverse PCP induced social withdrawal in rats (Boulay et al., 2004; Sams-Dodd, 1998a).
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
1.6. Aim The first objective of this study was to set up an automated method for studying social behaviour in rats as well as motor activity and aspects of movement pattern. Secondly we wanted to evaluate the effects of amphetamine and the non-competitive NMDA-receptor antagonist MK-801 on these variables in order to assess the method’s ability to model negative symptoms. We hypothesized that MK-801, unlike amphetamine, would induce social withdrawal.
2. Methods 2.1. Animals Male Sprague – Dawley rats (Scanbur BK AB, Sollentuna, Sweden) weighing 270 – 420 g at the time of testing were used in these experiments. Prior to testing the rats were housed for 1 week in reversed daylight cycle in groups of four or five in Macrolon type III cages. 2.2. Drugs d-Amphetamine sulphate (0.5, 1.0, 2.0 mg/kg bw; MW = 368.5, local pharmacy) and (+)-MK-801 hydrogen maleate (0.1, 0.2, 0.3 mg/kg bw; MW = 337.4, Research Biochemicals International, USA) were dissolved in saline. Injections were made intraperitoneally in volumes of 4 or 5 ml/kg.
829
recorder (Panasonic NV-HS850). The lamps were placed on either side of the lens and 47 cm apart, perpendicular to the length of the arenas. This arrangement minimized shading by the arena walls. See Fig. 1 for a schematic illustration of the setting. The videotapes were then analysed using the video-tracking software Ethovision\ 2.x Color Pro (Noldus Information Technology, Wageningen, The Netherlands) with sampling frequency set to 12.5 samples per second, and resolution set to medium (w/h: 768 576 pixels). The resulting tracks describing the animals’ movements in the arenas were exported for further analysis in other software. Conversion of the tracks from pixels to centimetres and correction for distortion, caused by the wide-angle lens, as well as extraction of variables from the tracks were performed in MatLab (The MathWorks, Inc., USA), using functions developed in our laboratory. 2.4. Experimental procedure Experiments were performed between 8 a.m. and 4 p.m. All handling of the animals in connection with the experiments was performed in dim light. Drug or vehicle injections were performed 30 min prior to testing, immediately followed by marking of the animals with fluorescent hair gel. One pair of rats was released in each arena and videotaped for 30 min. Two animals placed in the same arena (1) had since delivery been housed in
To VCR
2.3. Tracking procedure 47 cm
UV-lights
215 cm
Camera
cm
100 cm
150
This method has been modified from Sams-Dodd (1995b). The rats were studied in pairs in two open arenas (l/w/h: 150 100 40 cm), with the sides leaning slightly outwards (¨3-). The inner surfaces of the arenas were covered with black PVC foam plastic (Foam-X\, Alcan Airex AG, Switzerland). The plastic was selected for its light absorbing finish. The arenas were enclosed in a dark room with sound dampening walls and ceiling. In order to distinguish between two animals in the same arena, the rats were marked with fluorescent hair gel (Kryolan GmbH, Berlin, Germany), and the arenas were illuminated with two black light fluorescent lamps (Philips FTL_ 8W/08). One rat was marked with red hair gel and the other with a 50/50 mix of green and yellow. To attain the necessary level of fluorescence, a large part of the rats’ backs were covered with a rich layer of gel. From dying of the animals until the start (< 30 min) of the experiment, the rats were kept in separate cages. The animals were placed in the arenas and videotaped for 30 min, using a light sensitive video camera (Panasonic WVCP460, lens: Panasonic LA-408C3) placed 215 cm above the arenas and connected to an S-VHS videocassette
Fig. 1. The experimental setting used in this study to measure behavioural response to treatment with amphetamine and MK-801 is shown here. The rats are dyed with fluorescent hair gel and the arenas are illuminated with ultraviolet light. The animals in the arenas are videotaped using a light sensitive color video camera and the videotape is analysed off line in the video-tracking software EthoVision\.
830
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
separate cages, (2) received the same drug treatment and (3) were marked with gel of different colors.
A
Motor activity
16
2.5. Variables To assess motor activity, mean velocity was calculated for each animal. Prior to calculation of velocity the tracks were subjected to a running mean filter, i.e. each (Nth) sample was replaced by the average of the surrounding 15 (N 7 to N + 7) samples. This procedure removed most of the noise in the tracks, which may otherwise stand for a large portion of the measured
Velocity (cm/s)
14
Velocity (cm/s)
12 10 8 6 4
8 6 4
0 C
0.1
0.2
2
40 35 30 25 20 15 10 5 0 C
0.1
0.2
0.3
0.4
MK-801 (mg/kg) C
0.5
1
2
Amphetamine (mg/kg)
C
Social interactions
45 40
B
Time in inner zone Proximity (%)
70
Time in inner zone (%)
0.4
Time in inner zone
50 45
0
60 50 40
35 30 25 20 15 10
30
5
20
0 C
10
0.1
0.2
0.3
0.4
MK-801 (mg/kg)
0 C
0.5
1
2
Amphetamine (mg/kg)
C
0.3
MK-801 (mg/kg)
Time in inner zone (%)
Motor activity 14
10
2
B A
12
60
Social interactions
Fig. 3. Effects of (+)-MK-801 (0.1, 0.2, 0.3, 0.4 mg/kg) on (A) motor activity (velocity), (B) time spent in inner zone and (C) social behaviour (proximity). Shown are means with S.E.M. Treatment groups were compared with the control group using ANOVA followed by Dunnett’s post hoc test. *p < 0.5 and **p < 0.01. N = 6 – 12 pairs/group.
Proximity (%)
50 40 30 20 10 0 C
0.5
1
2
Amphetamine (mg/kg) Fig. 2. Effects of amphetamine (0.5, 1, 2 mg/kg) on (A) motor activity (velocity), (B) time spent in inner zone and (C) social behaviour (proximity). Shown are means with S.E.M. Comparisons are made with the control group using ANOVA followed by Dunnett’s post hoc test. *p < 0.5 and **p < 0.01. N = 4 pairs/group.
movement. The size of the running mean window was set to filter as much noise as possible while at the same time retaining sufficient information about the animals’ finer movements. The fraction of the observation period each animal spent in a defined inner zone was calculated. An animal is positioned in the inner zone whenever its center of gravity is located at least 10 cm away from the closest wall of the arena. FProximity_, measuring social behaviour, is the fraction of the observation period, which the animals spend within a defined distance apart. One Fin proximity_ period is initiated when the animals’ centers of gravity come
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
831
Amphetamine induced a significant dose-dependent increase in velocity, compared to controls, at all three doses (0.5, 1 and 2 mg/kg, N = 4 pairs/group, Fig. 2a). The time spent in the inner zone was also increased in a dose dependent manner. This effect was statistically significant at the two highest doses (Fig. 2b). There was a tendency, albeit not statistically significant, to increased social interactions measured as proximity (Fig. 2c). (+)-MK-801 (Control, 0.1, 0.2, 0.3, 0.4 mg/kg; N = 6 –12 pairs/group) significantly increased motor activity at the two highest doses tested (Fig. 3a). There was a tendency towards decreased time spent in the inner zone following MK-801 treatment (Fig. 3b). MK-801 induced a significant decrease in proximity (Fig. 3c).
schizophrenia, while NMDA-receptor antagonists induce both positive and negative symptoms. Social withdrawal in rats, in response to non-competitive NMDA-receptor antagonists, is an accepted model for negative symptoms of schizophrenia (see Ellenbroek and Cools, 2000). In this study single injections of amphetamine and MK-801 dose-dependently increased motor activity. These two activating drugs did, however, seem to have opposite effects on the other behaviours that were examined in this study. Amphetamine tended to stimulate social behaviour and significantly increased the time the rats spent in the inner zone. MK-801 acted inhibitory on both these variables. Since hyperactivity is believed to correspond to positive symptoms, and defective social interactions to negative symptoms (Nilsson et al., 2004; Sams-Dodd et al., 1997), the present data support the concept that NMDA-receptor antagonists may model both positive and negative symptoms of schizophrenia, while dopaminergic agonists only model positive symptoms. The tendency for amphetamine to increase social interactions is interesting, since amphetamine has been reported to alleviate negative symptoms of schizophrenia. The current results suggest that acute MK-801 treatment to rats reliably models both positive and negative symptoms of schizophrenia. Sams-Dodd (1995b), in contrast, judged it necessary to administer PCP subchronically in order to attain a credible model for negative symptoms. However, the almost instantaneous appearance of schizophrenia-like symptoms in human subjects following ketamine administration (Tamminga, 1999) supports the design used in the present study.
4. Discussion
5. Conclusion
Social deficits are considered to be a core negative symptom in schizophrenia. We have set up an automated method, similar to that of Sams-Dodd (1995b), for studying behaviour in two rats moving together in an open arena (l/w/ h: 150 100 40 cm), using an automated video-tracking system. We are able to assess a large number of different behaviours; however in the present study we focus on motor activity and social interactions. We have previously evaluated the methodology used by Sams-Dodd, which involves dying the hind part of one of the two animals black, thereby enabling the video-tracking system to distinguish between rats by difference in white surface area against the dark background. Since the surface area of any rat is affected by a number of behaviours, the system inevitably makes many mistakes that later must be corrected manually, a procedure that is highly tedious and time consuming. Therefore we have modified the method so that the system instead distinguishes between animals by color, hence minimizing the risk of the two rats being mixed up during the automatic analysis. The prevailing view is that dopaminergic agonists induce symptoms mimicking positive symptoms of
In the present study we present an automated method, modified from Sams-Dodd (1995b), for measuring motor activity, social behaviour and movement pattern in rats. By using this method we have shown that acute treatment with the NMDA-receptor antagonist MK-801, unlike amphetamine, induces social withdrawal, while both compounds induce hyperactivity. These results tally well with the notion that both dopaminergic agonists and NMDA-receptor antagonists model positive symptoms of schizophrenia, whereas only NMDA-receptor antagonists are capable of modelling negative symptoms.
within 20 cm apart, and ends when the distance exceeds 25 cm. 2.6. Statistics Each pair of rats is treated as one object in the statistical analysis. Therefore the mean value is calculated for the two animals in each pair. The data presented here are pooled from several experiments. In each experiment type all groups are compared with the control group using ANOVA followed by Dunnett’s post hoc test. Suspected outliers were excluded provided that they fulfilled the criteria defined by Dixon’s gap test.
3. Results
Acknowledgements This study was supported by grants from the Swedish Research Council (9067), Teodor Neranders fond, Stiftelsen Wilhelm och Martina Lundgrens Vetenkapsfond, Emil och Maria Palms stiftelse, Eva och Oscar Ahre´ns stiftelse and Stiftelsen Psykiatriska Forskningsfonden, Go¨teborg, Sweden.
832
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
References Allen, R.M., Young, S.J., 1978. Phencyclidine-induced psychosis. Am. J. Psychiatry 135 (9), 1081 – 1084. Angrist, B., Lee, H.K., Gershon, S., 1974a. The antagonism of amphetamine-induced symptomatology by a neuroleptic. Am. J. Psychiatry 131 (7), 817 – 819. Angrist, B., Sathananthan, G., Wilk, S., Gershon, S., 1974b. Amphetamine psychosis: behavioral and biochemical aspects. J. Psychiatr. Res. 11, 13 – 23. Arnt, J., 1998. Pharmacological differentiation of classical and novel antipsychotics. Int. Clin. Psychopharmacol. 13 (Suppl. 3), S7 – S14. Beamish, P., Kiloh, L.G., 1960. Psychoses due to amphetamine consumption. J. Ment. Sci. 106, 337 – 344. Blin, O., 1999. A comparative review of new antipsychotics. Can. J. Psychiatry 44 (3), 235 – 244. Boulay, D., Depoortere, R., Louis, C., Perrault, G., Griebel, G., Soubrie, P., 2004. SSR181507, a putative atypical antipsychotic with dopamine D(2) antagonist and 5-HT(1A) agonist activities: improvement of social interaction deficits induced by phencyclidine in rats. Neuropharmacology 46 (8), 1121 – 1129. Castner, S.A., Goldman-Rakic, P.S., Williams, G.V., 2004. Animal models of working memory: insights for targeting cognitive dysfunction in schizophrenia. Psychopharmacology (Berl.) 174 (1), 111 – 125. Ellenbroek, B.A., Cools, A.R., 2000. Animal models for the negative symptoms of schizophrenia. Behav. Pharmacol. 11 (3 – 4), 223 – 233. File, S.E., 1980. The use of social interaction as a method for detecting anxiolytic activity of chlordiazepoxide-like drugs. J. Neurosci. Methods 2 (3), 219 – 238. File, S.E., Seth, P., 2003. A review of 25 years of the social interaction test. Eur. J. Pharmacol. 463 (1 – 3), 35 – 53. Goetz, C.G., Vogel, C., Tanner, C.M., Stebbins, G.T., 1998. Early dopaminergic drug-induced hallucinations in parkinsonian patients. Neurology 51 (3), 811 – 814. Jha, A., Fourie, H., 1999. Risperidone treatment of amphetamine psychosis. Br. J. Psychiatry 174, 366. Klawans, H.L., 1988. Psychiatric side effects during the treatment of Parkinson’s disease. J. Neural Transm., Suppl. 27, 117 – 122. Kokkinidis, L., Anisman, H., 1981. Amphetamine psychosis and schizophrenia: a dual model. Neurosci. Biobehav. Rev. 5 (4), 449 – 461. Lahti, A.C., Koffel, B., LaPorte, D., Tamminga, C.A., 1995. Subanesthetic doses of ketamine stimulate psychosis in schizophrenia. Neuropsychopharmacology 13 (1), 9 – 19. Lahti, A.C., Weiler, M.A., Tamara Michaelidis, B.A., Parwani, A., Tamminga, C.A., 2001. Effects of ketamine in normal and schizophrenic volunteers. Neuropsychopharmacology 25 (4), 455 – 467. Lodge, D., Anis, N.A., 1982. Effects of phencyclidine on excitatory amino acid activation of spinal interneurones in the cat. Eur. J. Pharmacol. 77 (2 – 3), 203 – 204.
Lodge, D., Jones, M., Fletcher, E., 1994. Non-competitive antagonists of Nmethyl-d-aspartate. In: Collingridge, G.L., Watkins, J.C. (Eds.), The NMDA Receptor. Oxford University Press, Oxford, pp. 105 – 131. Luby, E.D., Cohen, B.D., Rosenbaum, G., Gottlieb, J.S., Kelley, R., 1959. Study of a new schizophrenomimetic drug: Sernyl. Arch. Neurol. Psychiatry 81, 363 – 369. Misra, L., Kofoed, L., 1997. Risperidone treatment of methamphetamine psychosis. Am. J. Psychiatry 154 (8), 1170. Nilsson, M., Carlsson, A., Ryden Markinhuhta, K., Sonesson, C., Pettersson, F., Gullme, M., Carlsson, M.L., 2004. The dopaminergic stabiliser ACR16 counteracts the behavioural primitivization induced by the NMDA receptor antagonist MK-801 in mice: implications for cognition. Prog. Neuro-Psychopharmacol. Biol. Psychiatry 28 (4), 677 – 685. Sams-Dodd, F., 1995a. Distinct effects of d-amphetamine and phencyclidine on the social behaviour of rats. Behav. Pharmacol. 6 (1), 55 – 65. Sams-Dodd, F., 1995b. Automation of the social interaction test by a videotracking system: behavioural effects of repeated phencyclidine treatment. J. Neurosci. Methods 59 (2), 157 – 167. Sams-Dodd, F., 1998a. Effects of diazepam, citalopram, methadone and naloxone on PCP-induced stereotyped behaviour and social isolation in the rat social interaction test. Neurosci. Biobehav. Rev. 23 (2), 287 – 293. Sams-Dodd, F., 1998b. Effects of dopamine agonists and antagonists on PCP-induced stereotyped behaviour and social isolation in the rat social interaction test. Psychopharmacology (Berl.) 135 (2), 182 – 193. Sams-Dodd, F., Lipska, B.K., Weinberger, D.R., 1997. Neonatal lesions of the rat ventral hippocampus result in hyperlocomotion and deficits in social behaviour in adulthood. Psychopharmacology (Berl.) 132 (3), 303 – 310. Sanfilipo, M., Wolkin, A., Angrist, B., van Kammen, D.P., Duncan, E., Wieland, S., Cooper, T.B., Peselow, E.D., Rotrosen, J., 1996. Amphetamine and negative symptoms of schizophrenia. Psychopharmacology 123 (2), 211 – 214. Snyder, S.H., 1980. Phencyclidine. Nature 285 (5764), 355 – 356. Tamminga, C., 1999. Glutamatergic aspects of schizophrenia. Br. J. Psychiatr., Suppl. (37), 12 – 15. Van Kammen, D.P., Boronow, J.J., 1988. Dextro-amphetamine diminishes negative symptoms in schizophrenia. Int. Clin. Psychopharmacol. 3 (2), 111 – 121. Weiner, I.B., 1964. Differential diagnosis in amphetamine psychosis. Psychiatr. Q. 38 (4), 707 – 714. West, A.P., 1974. Interaction of low-dose amphetamine use with schizophrenia in outpatients: three case reports. Am. J. Psychiatry 13 (3), 321 – 323. Wieronska, J.M., Szewczyk, B., Palucha, A., Branski, P., Smialowska, M., 2003. Involvement of CRF but not NPY in the anxiety regulation via NMDA receptors. Pol. J. Pharmacol. 55 (6), 1119 – 1124. Young, D., Scoville, W.B., 1938. Paranoid psychosis in narcolepsy and the possible danger of benzedrine treatment. Med. Clin. North Am. 22, 637 – 646.
(+)-MK-801 induced social withdrawal in rats; a model for negative symptoms of schizophrenia Johan P. Runga,T, Arvid Carlssona, Katarina Ryde´n Markinhuhtab, Maria L. Carlssona a
The Arvid Carlsson Institute for Neuroscience, Institute of Clinical Neuroscience, The Sahlgrenska Academy, Go¨teborg University, Medicinaregatan 11, SE-405 30 Go¨teborg, Sweden b A Carlsson Research AB, Biotech Center, Arvid Wallgrens Backe 20, SE-413 46 Go¨teborg, Sweden Accepted 1 March 2005 Available online 23 May 2005
Abstract Dopaminergic agonists and NMDA-receptor antagonists form the basis for the dopamine and glutamate models of schizophrenia, respectively. In human subjects dopaminergic agonists evoke a psychosis resembling positive symptoms of schizophrenia, while NMDAreceptor antagonists produce both positive and negative symptoms. Consequently, the glutamate model may be considered the most complete of the two models. Alterations in animal behaviour, in response to amphetamine or NMDA-receptor antagonists, are widely used to model schizophrenia. NMDA-receptor antagonist induced social withdrawal in rat is an established model for negative symptoms of schizophrenia. In this study we have set up an automated method, based on video tracking, to assess social behaviour, motor activity and movement pattern in rats. This method was then used to evaluate the effects of amphetamine and the NMDA-receptor antagonist (+)-MK-801, administered as single intraperitoneal injections, on rat behaviour. Amphetamine caused significantly increased motor activity and a tendency towards stimulation of social interactions. (+)-MK-801 also stimulated motor activity, but induced a significant inhibition of social interactions. These results indicate that a single injection of (+)-MK-801 to rats models both positive and negative symptoms of schizophrenia. Amphetamine, in contrast, reflects only the positive symptoms of schizophrenia in this model. D 2005 Elsevier Inc. All rights reserved. Keywords: Amphetamine; (+)-MK-801; Negative symptoms; Rat; Schizophrenia; Social withdrawal; Video tracking
1. Introduction
1.2. Amphetamine psychosis and the dopamine hypothesis for schizophrenia
1.1. Models for schizophrenia The two main models or hypotheses for schizophrenia are the dopamine and the glutamate hypotheses for this disorder. The hyperdopaminergia model prevailed until the late 1980s when the glutamate model started to gain ground. Abbreviations: D2-receptor, dopaminergic D2-receptor; NMDA, N-methyl-d-aspartate; PCP, phencyclidine. * Corresponding author. The Arvid Carlsson Institute for Neuroscience, Institute of Clinical Neuroscience, The Sahlgrenska Academy, Go¨teborg University, Box 432, SE-405 30 Go¨teborg, Sweden. Tel.: +46 31 773 33 28; fax: +46 31 773 34 01. E-mail address: [email protected] (J.P. Rung). 0278-5846/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.pnpbp.2005.03.004
Prolonged high dose self-administration, and occasionally even a single injection of amphetamine, are known to cause a psychosis typically characterized by paranoid delusions and hallucinations (Kokkinidis and Anisman, 1981; Young and Scoville, 1938), thus displaying resemblance to positive symptoms of schizophrenia (Beamish and Kiloh, 1960). This phenomenon has also been studied extensively under controlled conditions in the clinic with known doses (Angrist et al., 1974b). In individuals predisposed for developing schizophrenia even small doses of amphetamine may induce psychosis (West, 1974). On the other hand, low doses of amphetamine generally have beneficial effects on performance, attention, mood, social
828
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
abilities and results in intelligence tests (Weiner, 1964). There are no convincing reports of dopaminergic stimulators inducing behavioural or mental aberrations resembling negative symptoms of schizophrenia. Amphetamine has even been suggested to have a mitigating effect on negative symptoms in some schizophrenics (Sanfilipo et al., 1996; Van Kammen and Boronow, 1988). Amphetamines augment dopaminergic and noradrenergic neurotransmission by inducing catecholamine release and preventing catecholamine reuptake. Although the effect is not specific for dopamine, the prevailing view is that dopaminergic mechanisms underlie amphetamine psychosis. Furthermore, virtually all currently used antipsychotic agents suppress dopaminergic neurotransmission. Reports of at least some of these drugs alleviating symptoms of amphetamine psychosis (Angrist et al., 1974a; Jha and Fourie, 1999; Misra and Kofoed, 1997) provide support for both the dopamine hypothesis and the amphetamine model for schizophrenia. The dopamine hypothesis is further supported by the fact that patients suffering from Parkinson’s disease (PD) are known to develop paranoid delusions and hallucinations, mainly visual, following sustained (> 1 year) lDOPA treatment (Goetz et al., 1998; Klawans, 1988). It has been reported that PD patients with latent psychotic illness may experience hallucinations much sooner (< 3 months) after onset of l-DOPA treatment (Goetz et al., 1998).
receptor antagonists, MK-801 is by far the most potent (Lodge et al., 1994).
1.3. The phencyclidine or glutamate model for schizophrenia
1.5. Animal models for schizophrenia
The first and most striking support for the glutamate or phencyclidine model for schizophrenia is provided by the observation that phencyclidine (PCP) induces a psychotic state that includes both positive and negative symptoms in healthy individuals (Luby et al., 1959; Snyder, 1980). It should be recalled in this context, however, that the glutamate receptor blocking properties of PCP were not disclosed until 1982 (Lodge and Anis, 1982). Later, psychotomimetic effects were demonstrated with ketamine as well (Tamminga, 1999). Interestingly, Tamminga et al. (Lahti et al., 1995, 2001; Tamminga, 1999) found that schizophrenic patients exposed to ketamine experienced worsening or reappearance of positive symptoms characteristic of their individual psychoses. Surprisingly, these patients did not experience worsening of negative symptoms. This was hypothesized to be due to the high baseline in these individuals, with respect to negative symptoms, leading to a ceiling effect. PCP, ketamine and the hitherto not mentioned substance (+)-MK-801 (MK-801) all belong to a group of noncompetitive antagonists acting at the glutamatergic Nmethyl-d-aspartate (NMDA)-receptor complex, binding to a site located within the ion channel and blocking cation flow. Due to the location of the binding site, the ion channel needs to be open for these antagonists to bind, thus making the antagonism agonist dependent. Among these NMDA-
1.4. Advantage of the glutamate model Psychosis resulting from dopaminergic stimulation indeed shares many similarities with positive symptoms of schizophrenia, but does not include any characteristics that match negative symptoms. Furthermore, classic neuroleptics with pronounced dopamine D2-receptor blockade do not, in general, alleviate the negative symptoms in schizophrenic patients (see Blin, 1999). Taken together, these observations indicate that hyperdopaminergia is not directly responsible for negative symptoms in schizophrenia. In contrast, as mentioned above, dopamine agonists have been used successfully to treat negative symptoms. NMDA-receptor antagonists on the other hand produce a psychotic state that includes both negative and positive symptoms. Furthermore, at least l-DOPA induced psychosis typically involves visual hallucinations, whereas NMDAreceptor antagonists reportedly cause auditory hallucinations (Allen and Young, 1978). The hallucinations in schizophrenia are considered to be mainly auditory, often consisting of inner voices. Thus, we may conclude that NMDA-receptor antagonists provide a more complete model for schizophrenia than do dopaminergic agonists.
NMDA-receptor antagonists and dopaminergic agonists administered to mammals constitute two widely used animal models for schizophrenia. Behavioural studies performed in rodents treated with these substances reveal behaviours that correspond to different symptoms of schizophrenia. The perhaps most studied behavioural aspect is motor activity. Drug induced hyperactivity in rodents may correspond to positive symptoms of schizophrenia (Nilsson et al., 2004; Sams-Dodd et al., 1997). Cognitive deficits may be modelled with memory and learning tasks (Arnt, 1998). Social withdrawal is a core negative symptom in schizophrenia and may be modelled by various drug treatments in animals (Sams-Dodd et al., 1997). The prevailing view seems to be that unlike NMDA-receptor antagonists amphetamine does not induce social withdrawal (Sams-Dodd, 1995a, 1998b), although there are reports of amphetamine hampering social behaviour in non-human primates (Castner et al., 2004). However, this latter finding does not tally with observations in human subjects. It should be mentioned in this context that social withdrawal in rodents is also used for modelling anxiety (File, 1980; File and Seth, 2003). However, in the literature NMDA-receptor antagonists are described as being both anxiolytic (Wieronska et al., 2003) and anxiogenic (File and Seth, 2003). Furthermore, the anxiolytic drug diazepam does not seem to reverse PCP induced social withdrawal in rats (Boulay et al., 2004; Sams-Dodd, 1998a).
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
1.6. Aim The first objective of this study was to set up an automated method for studying social behaviour in rats as well as motor activity and aspects of movement pattern. Secondly we wanted to evaluate the effects of amphetamine and the non-competitive NMDA-receptor antagonist MK-801 on these variables in order to assess the method’s ability to model negative symptoms. We hypothesized that MK-801, unlike amphetamine, would induce social withdrawal.
2. Methods 2.1. Animals Male Sprague – Dawley rats (Scanbur BK AB, Sollentuna, Sweden) weighing 270 – 420 g at the time of testing were used in these experiments. Prior to testing the rats were housed for 1 week in reversed daylight cycle in groups of four or five in Macrolon type III cages. 2.2. Drugs d-Amphetamine sulphate (0.5, 1.0, 2.0 mg/kg bw; MW = 368.5, local pharmacy) and (+)-MK-801 hydrogen maleate (0.1, 0.2, 0.3 mg/kg bw; MW = 337.4, Research Biochemicals International, USA) were dissolved in saline. Injections were made intraperitoneally in volumes of 4 or 5 ml/kg.
829
recorder (Panasonic NV-HS850). The lamps were placed on either side of the lens and 47 cm apart, perpendicular to the length of the arenas. This arrangement minimized shading by the arena walls. See Fig. 1 for a schematic illustration of the setting. The videotapes were then analysed using the video-tracking software Ethovision\ 2.x Color Pro (Noldus Information Technology, Wageningen, The Netherlands) with sampling frequency set to 12.5 samples per second, and resolution set to medium (w/h: 768 576 pixels). The resulting tracks describing the animals’ movements in the arenas were exported for further analysis in other software. Conversion of the tracks from pixels to centimetres and correction for distortion, caused by the wide-angle lens, as well as extraction of variables from the tracks were performed in MatLab (The MathWorks, Inc., USA), using functions developed in our laboratory. 2.4. Experimental procedure Experiments were performed between 8 a.m. and 4 p.m. All handling of the animals in connection with the experiments was performed in dim light. Drug or vehicle injections were performed 30 min prior to testing, immediately followed by marking of the animals with fluorescent hair gel. One pair of rats was released in each arena and videotaped for 30 min. Two animals placed in the same arena (1) had since delivery been housed in
To VCR
2.3. Tracking procedure 47 cm
UV-lights
215 cm
Camera
cm
100 cm
150
This method has been modified from Sams-Dodd (1995b). The rats were studied in pairs in two open arenas (l/w/h: 150 100 40 cm), with the sides leaning slightly outwards (¨3-). The inner surfaces of the arenas were covered with black PVC foam plastic (Foam-X\, Alcan Airex AG, Switzerland). The plastic was selected for its light absorbing finish. The arenas were enclosed in a dark room with sound dampening walls and ceiling. In order to distinguish between two animals in the same arena, the rats were marked with fluorescent hair gel (Kryolan GmbH, Berlin, Germany), and the arenas were illuminated with two black light fluorescent lamps (Philips FTL_ 8W/08). One rat was marked with red hair gel and the other with a 50/50 mix of green and yellow. To attain the necessary level of fluorescence, a large part of the rats’ backs were covered with a rich layer of gel. From dying of the animals until the start (< 30 min) of the experiment, the rats were kept in separate cages. The animals were placed in the arenas and videotaped for 30 min, using a light sensitive video camera (Panasonic WVCP460, lens: Panasonic LA-408C3) placed 215 cm above the arenas and connected to an S-VHS videocassette
Fig. 1. The experimental setting used in this study to measure behavioural response to treatment with amphetamine and MK-801 is shown here. The rats are dyed with fluorescent hair gel and the arenas are illuminated with ultraviolet light. The animals in the arenas are videotaped using a light sensitive color video camera and the videotape is analysed off line in the video-tracking software EthoVision\.
830
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
separate cages, (2) received the same drug treatment and (3) were marked with gel of different colors.
A
Motor activity
16
2.5. Variables To assess motor activity, mean velocity was calculated for each animal. Prior to calculation of velocity the tracks were subjected to a running mean filter, i.e. each (Nth) sample was replaced by the average of the surrounding 15 (N 7 to N + 7) samples. This procedure removed most of the noise in the tracks, which may otherwise stand for a large portion of the measured
Velocity (cm/s)
14
Velocity (cm/s)
12 10 8 6 4
8 6 4
0 C
0.1
0.2
2
40 35 30 25 20 15 10 5 0 C
0.1
0.2
0.3
0.4
MK-801 (mg/kg) C
0.5
1
2
Amphetamine (mg/kg)
C
Social interactions
45 40
B
Time in inner zone Proximity (%)
70
Time in inner zone (%)
0.4
Time in inner zone
50 45
0
60 50 40
35 30 25 20 15 10
30
5
20
0 C
10
0.1
0.2
0.3
0.4
MK-801 (mg/kg)
0 C
0.5
1
2
Amphetamine (mg/kg)
C
0.3
MK-801 (mg/kg)
Time in inner zone (%)
Motor activity 14
10
2
B A
12
60
Social interactions
Fig. 3. Effects of (+)-MK-801 (0.1, 0.2, 0.3, 0.4 mg/kg) on (A) motor activity (velocity), (B) time spent in inner zone and (C) social behaviour (proximity). Shown are means with S.E.M. Treatment groups were compared with the control group using ANOVA followed by Dunnett’s post hoc test. *p < 0.5 and **p < 0.01. N = 6 – 12 pairs/group.
Proximity (%)
50 40 30 20 10 0 C
0.5
1
2
Amphetamine (mg/kg) Fig. 2. Effects of amphetamine (0.5, 1, 2 mg/kg) on (A) motor activity (velocity), (B) time spent in inner zone and (C) social behaviour (proximity). Shown are means with S.E.M. Comparisons are made with the control group using ANOVA followed by Dunnett’s post hoc test. *p < 0.5 and **p < 0.01. N = 4 pairs/group.
movement. The size of the running mean window was set to filter as much noise as possible while at the same time retaining sufficient information about the animals’ finer movements. The fraction of the observation period each animal spent in a defined inner zone was calculated. An animal is positioned in the inner zone whenever its center of gravity is located at least 10 cm away from the closest wall of the arena. FProximity_, measuring social behaviour, is the fraction of the observation period, which the animals spend within a defined distance apart. One Fin proximity_ period is initiated when the animals’ centers of gravity come
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
831
Amphetamine induced a significant dose-dependent increase in velocity, compared to controls, at all three doses (0.5, 1 and 2 mg/kg, N = 4 pairs/group, Fig. 2a). The time spent in the inner zone was also increased in a dose dependent manner. This effect was statistically significant at the two highest doses (Fig. 2b). There was a tendency, albeit not statistically significant, to increased social interactions measured as proximity (Fig. 2c). (+)-MK-801 (Control, 0.1, 0.2, 0.3, 0.4 mg/kg; N = 6 –12 pairs/group) significantly increased motor activity at the two highest doses tested (Fig. 3a). There was a tendency towards decreased time spent in the inner zone following MK-801 treatment (Fig. 3b). MK-801 induced a significant decrease in proximity (Fig. 3c).
schizophrenia, while NMDA-receptor antagonists induce both positive and negative symptoms. Social withdrawal in rats, in response to non-competitive NMDA-receptor antagonists, is an accepted model for negative symptoms of schizophrenia (see Ellenbroek and Cools, 2000). In this study single injections of amphetamine and MK-801 dose-dependently increased motor activity. These two activating drugs did, however, seem to have opposite effects on the other behaviours that were examined in this study. Amphetamine tended to stimulate social behaviour and significantly increased the time the rats spent in the inner zone. MK-801 acted inhibitory on both these variables. Since hyperactivity is believed to correspond to positive symptoms, and defective social interactions to negative symptoms (Nilsson et al., 2004; Sams-Dodd et al., 1997), the present data support the concept that NMDA-receptor antagonists may model both positive and negative symptoms of schizophrenia, while dopaminergic agonists only model positive symptoms. The tendency for amphetamine to increase social interactions is interesting, since amphetamine has been reported to alleviate negative symptoms of schizophrenia. The current results suggest that acute MK-801 treatment to rats reliably models both positive and negative symptoms of schizophrenia. Sams-Dodd (1995b), in contrast, judged it necessary to administer PCP subchronically in order to attain a credible model for negative symptoms. However, the almost instantaneous appearance of schizophrenia-like symptoms in human subjects following ketamine administration (Tamminga, 1999) supports the design used in the present study.
4. Discussion
5. Conclusion
Social deficits are considered to be a core negative symptom in schizophrenia. We have set up an automated method, similar to that of Sams-Dodd (1995b), for studying behaviour in two rats moving together in an open arena (l/w/ h: 150 100 40 cm), using an automated video-tracking system. We are able to assess a large number of different behaviours; however in the present study we focus on motor activity and social interactions. We have previously evaluated the methodology used by Sams-Dodd, which involves dying the hind part of one of the two animals black, thereby enabling the video-tracking system to distinguish between rats by difference in white surface area against the dark background. Since the surface area of any rat is affected by a number of behaviours, the system inevitably makes many mistakes that later must be corrected manually, a procedure that is highly tedious and time consuming. Therefore we have modified the method so that the system instead distinguishes between animals by color, hence minimizing the risk of the two rats being mixed up during the automatic analysis. The prevailing view is that dopaminergic agonists induce symptoms mimicking positive symptoms of
In the present study we present an automated method, modified from Sams-Dodd (1995b), for measuring motor activity, social behaviour and movement pattern in rats. By using this method we have shown that acute treatment with the NMDA-receptor antagonist MK-801, unlike amphetamine, induces social withdrawal, while both compounds induce hyperactivity. These results tally well with the notion that both dopaminergic agonists and NMDA-receptor antagonists model positive symptoms of schizophrenia, whereas only NMDA-receptor antagonists are capable of modelling negative symptoms.
within 20 cm apart, and ends when the distance exceeds 25 cm. 2.6. Statistics Each pair of rats is treated as one object in the statistical analysis. Therefore the mean value is calculated for the two animals in each pair. The data presented here are pooled from several experiments. In each experiment type all groups are compared with the control group using ANOVA followed by Dunnett’s post hoc test. Suspected outliers were excluded provided that they fulfilled the criteria defined by Dixon’s gap test.
3. Results
Acknowledgements This study was supported by grants from the Swedish Research Council (9067), Teodor Neranders fond, Stiftelsen Wilhelm och Martina Lundgrens Vetenkapsfond, Emil och Maria Palms stiftelse, Eva och Oscar Ahre´ns stiftelse and Stiftelsen Psykiatriska Forskningsfonden, Go¨teborg, Sweden.
832
J.P. Rung et al. / Progress in Neuro-Psychopharmacology & Biological Psychiatry 29 (2005) 827 – 832
References Allen, R.M., Young, S.J., 1978. Phencyclidine-induced psychosis. Am. J. Psychiatry 135 (9), 1081 – 1084. Angrist, B., Lee, H.K., Gershon, S., 1974a. The antagonism of amphetamine-induced symptomatology by a neuroleptic. Am. J. Psychiatry 131 (7), 817 – 819. Angrist, B., Sathananthan, G., Wilk, S., Gershon, S., 1974b. Amphetamine psychosis: behavioral and biochemical aspects. J. Psychiatr. Res. 11, 13 – 23. Arnt, J., 1998. Pharmacological differentiation of classical and novel antipsychotics. Int. Clin. Psychopharmacol. 13 (Suppl. 3), S7 – S14. Beamish, P., Kiloh, L.G., 1960. Psychoses due to amphetamine consumption. J. Ment. Sci. 106, 337 – 344. Blin, O., 1999. A comparative review of new antipsychotics. Can. J. Psychiatry 44 (3), 235 – 244. Boulay, D., Depoortere, R., Louis, C., Perrault, G., Griebel, G., Soubrie, P., 2004. SSR181507, a putative atypical antipsychotic with dopamine D(2) antagonist and 5-HT(1A) agonist activities: improvement of social interaction deficits induced by phencyclidine in rats. Neuropharmacology 46 (8), 1121 – 1129. Castner, S.A., Goldman-Rakic, P.S., Williams, G.V., 2004. Animal models of working memory: insights for targeting cognitive dysfunction in schizophrenia. Psychopharmacology (Berl.) 174 (1), 111 – 125. Ellenbroek, B.A., Cools, A.R., 2000. Animal models for the negative symptoms of schizophrenia. Behav. Pharmacol. 11 (3 – 4), 223 – 233. File, S.E., 1980. The use of social interaction as a method for detecting anxiolytic activity of chlordiazepoxide-like drugs. J. Neurosci. Methods 2 (3), 219 – 238. File, S.E., Seth, P., 2003. A review of 25 years of the social interaction test. Eur. J. Pharmacol. 463 (1 – 3), 35 – 53. Goetz, C.G., Vogel, C., Tanner, C.M., Stebbins, G.T., 1998. Early dopaminergic drug-induced hallucinations in parkinsonian patients. Neurology 51 (3), 811 – 814. Jha, A., Fourie, H., 1999. Risperidone treatment of amphetamine psychosis. Br. J. Psychiatry 174, 366. Klawans, H.L., 1988. Psychiatric side effects during the treatment of Parkinson’s disease. J. Neural Transm., Suppl. 27, 117 – 122. Kokkinidis, L., Anisman, H., 1981. Amphetamine psychosis and schizophrenia: a dual model. Neurosci. Biobehav. Rev. 5 (4), 449 – 461. Lahti, A.C., Koffel, B., LaPorte, D., Tamminga, C.A., 1995. Subanesthetic doses of ketamine stimulate psychosis in schizophrenia. Neuropsychopharmacology 13 (1), 9 – 19. Lahti, A.C., Weiler, M.A., Tamara Michaelidis, B.A., Parwani, A., Tamminga, C.A., 2001. Effects of ketamine in normal and schizophrenic volunteers. Neuropsychopharmacology 25 (4), 455 – 467. Lodge, D., Anis, N.A., 1982. Effects of phencyclidine on excitatory amino acid activation of spinal interneurones in the cat. Eur. J. Pharmacol. 77 (2 – 3), 203 – 204.
Lodge, D., Jones, M., Fletcher, E., 1994. Non-competitive antagonists of Nmethyl-d-aspartate. In: Collingridge, G.L., Watkins, J.C. (Eds.), The NMDA Receptor. Oxford University Press, Oxford, pp. 105 – 131. Luby, E.D., Cohen, B.D., Rosenbaum, G., Gottlieb, J.S., Kelley, R., 1959. Study of a new schizophrenomimetic drug: Sernyl. Arch. Neurol. Psychiatry 81, 363 – 369. Misra, L., Kofoed, L., 1997. Risperidone treatment of methamphetamine psychosis. Am. J. Psychiatry 154 (8), 1170. Nilsson, M., Carlsson, A., Ryden Markinhuhta, K., Sonesson, C., Pettersson, F., Gullme, M., Carlsson, M.L., 2004. The dopaminergic stabiliser ACR16 counteracts the behavioural primitivization induced by the NMDA receptor antagonist MK-801 in mice: implications for cognition. Prog. Neuro-Psychopharmacol. Biol. Psychiatry 28 (4), 677 – 685. Sams-Dodd, F., 1995a. Distinct effects of d-amphetamine and phencyclidine on the social behaviour of rats. Behav. Pharmacol. 6 (1), 55 – 65. Sams-Dodd, F., 1995b. Automation of the social interaction test by a videotracking system: behavioural effects of repeated phencyclidine treatment. J. Neurosci. Methods 59 (2), 157 – 167. Sams-Dodd, F., 1998a. Effects of diazepam, citalopram, methadone and naloxone on PCP-induced stereotyped behaviour and social isolation in the rat social interaction test. Neurosci. Biobehav. Rev. 23 (2), 287 – 293. Sams-Dodd, F., 1998b. Effects of dopamine agonists and antagonists on PCP-induced stereotyped behaviour and social isolation in the rat social interaction test. Psychopharmacology (Berl.) 135 (2), 182 – 193. Sams-Dodd, F., Lipska, B.K., Weinberger, D.R., 1997. Neonatal lesions of the rat ventral hippocampus result in hyperlocomotion and deficits in social behaviour in adulthood. Psychopharmacology (Berl.) 132 (3), 303 – 310. Sanfilipo, M., Wolkin, A., Angrist, B., van Kammen, D.P., Duncan, E., Wieland, S., Cooper, T.B., Peselow, E.D., Rotrosen, J., 1996. Amphetamine and negative symptoms of schizophrenia. Psychopharmacology 123 (2), 211 – 214. Snyder, S.H., 1980. Phencyclidine. Nature 285 (5764), 355 – 356. Tamminga, C., 1999. Glutamatergic aspects of schizophrenia. Br. J. Psychiatr., Suppl. (37), 12 – 15. Van Kammen, D.P., Boronow, J.J., 1988. Dextro-amphetamine diminishes negative symptoms in schizophrenia. Int. Clin. Psychopharmacol. 3 (2), 111 – 121. Weiner, I.B., 1964. Differential diagnosis in amphetamine psychosis. Psychiatr. Q. 38 (4), 707 – 714. West, A.P., 1974. Interaction of low-dose amphetamine use with schizophrenia in outpatients: three case reports. Am. J. Psychiatry 13 (3), 321 – 323. Wieronska, J.M., Szewczyk, B., Palucha, A., Branski, P., Smialowska, M., 2003. Involvement of CRF but not NPY in the anxiety regulation via NMDA receptors. Pol. J. Pharmacol. 55 (6), 1119 – 1124. Young, D., Scoville, W.B., 1938. Paranoid psychosis in narcolepsy and the possible danger of benzedrine treatment. Med. Clin. North Am. 22, 637 – 646.