G. Georgiadou 1 , V. Grivas 1 , P.A. Tarantilis 2 , M.G. Polissiou 2 , N. Pitsikas 1

1. Crocins, the active constituents of Crocus Sativus L., antagonized psychotomimetic effects produced by the NMDA receptor antagonist ketamine in rats G. Georgiadou1, V. Grivas1, P.A. Tarantilis2, M.G. Polissiou2, N. Pitsikas1 1Department of Pharmacology, School of Medicine, University of Thessaly, Larissa, Greece 2Laboratory of Chemistry, Department of Science, Agricultural University of Athens, Greece RESULTS INTRODUCTION Introduction Crocus Sativus L., commonly known as saffron, is a plant cultivated in various parts of the world. Among its active constituents are crocins, which are considered responsible for some of the plant’s numerous therapeutic effects. Experimental evidence shows that crocins affect cognition [1] and possess anxiolytic [2] and antidepressant properties [3]. There is experimental evidence that ketamine, a non–competitive N-methyl-D-aspartate (NMDA) receptor antagonist impairs cognition [6] and produces psychotomimetic effects in rodents [4,5]. Ketamine, thus, is widely used as an animal model of schizophrenia. The aim of the present study was to investigate the efficacy of crocins in counteracting these ketamine–induced psychotomimetic effects in rats. For this purpose, the ability of crocins to antagonize ketamine-induced hypermotility, stereotypies and ataxia was evaluated in an open field procedure. Further, using the social interaction paradigm we assessed the ability of crocins to counteract ketamine-induced social withdrawal. Finally, the ability of crocins to antagonize recognition memory deficits produced by ketamine were evaluated in the novel object recognition memory task (NORT). Open field test Pretreatment with crocins (50 mg/kg) counteracted some stereotypies and ataxia induced by ketamine (Tab. 1). Further, crocins (50 mg/kg) antagonized ketamine-induced hypermotility (Fig. 1). Table 1. Effects of crocins on ketamine-induced stereotypies and ataxia. Results are expressed as medians and interquartile range. CMWC = circling movement within cage. * P<0.05 vs. vehicle+vehicle-treated rats. # P<0.05 vs. vehicle+ketamine-treated rats. + P<0.05 vs. ketamine+crocins 50 mg/kg-treated rats . Figure 1. Effects of crocins on ketamine-induced hypermotility. Results are expressed as mean ± S.E.M. *P<0.05 vs. all the other groups except the ketamine+crocins (30 mg/kg). INTRODUCTION Social interaction test Pretreatment with crocins (50 mg/kg) reversed the social withdrawal caused by repeated administration of ketamine (8 mg/kg) without affecting animals’ motor activity (Fig. 2). MATERIAL AND METHODS Subjects Male, 3-month-old Wistar rats weighing 250-300 g were used in this study. Drugs Crocins were isolated from the red dried stigmas of Crocus Sativus L. Crocins and ketamine were dissolved in saline (NaCl 0.9%) and were administered intraperitoneally ( i.p.) in volume of 1 ml/kg. Control animals received isovolumetric amounts of saline. Open field test In order to evaluate hyperlocomotion, stereotyped behaviour (head weaving, body sway, continuous movement within the whole cage) and ataxia, each rat, immediately after drug administration,was placed in a single observation cage for 10 min. and was scored every 60 s. for the presence of each one of these parameters. Social interaction test Animals received saline or ketamine for 2 consecutive days. On the testing day 3, animals received the appropriate treatment and each pair of rats 30 min after treatment was placed in a single observation cage for 10 min. The total time spent in social interaction (sniffing, grooming, following, climbing, biting, fighting, mounting) was recorded [5]. Novel Object Recognition Test (NORT) NORT was performed as described [6]. Compounds were injected just after T1. Figure 2. Effects of crocins on ketamine-induced impairments in the social interaction test. Results are expressed as mean ± S.E.M. *,+P<0,05 vs. all the other groups. NORT Post-training administration of crocins (15 and 30 mg/kg) reversed recognition memory deficits induced by ketamine. Crocins did not affect rats’ exploratory activity and motility (Fig. 3). Figure 3. NORT. Effects of crocins on rats’ performance during T2 expressed by the discrimination index D (D=N-F/N+F) N is the time of exploration of the novel object and F is that of exploration of the familiar object.Results are expressed as mean ± S.E.M. *P<0.05 vs. all the other groups. CONCLUSIONS • Pretreatment with crocins attenuated stereotyped circling movements, ataxia and hyperactivity induced by ketamine. • 2. Pretreatment with crocins reversed social withdrawal caused by repeated administration of ketamine in the social interaction test. • 3. Post-training administration of crocins antagonized ketamine-induced recognition memory deficits. • 4. Our findings indicate that crocins are sensitive to glutamatergic hypofunction and might constitute a potential candidate for the treatment of schizophrenia. Acknowledgements This work was co-financed by the European Union and Greek National Funds through the Research Funding Program Heracleitus II by the grant 4190.01.17 to G.G. The present study was also supported by a grant of the Research Committee of the University of Thessaly (no. 3219) to N.P. • References • Pitsikas et al., Behav Brain Res 183:141-6, 2007. • Pitsikas et al., Phytomedicine 15:1135-9, 2008. • Akhondzadeh et al., ProgNeuropsychopharmacolBiol Psychiatry 31:439-42, 2007. • Razouxet al.,Neuropsychopharmacology 32:719-27,2007. • 5. Koros et al., Neuropsychopharmacology 32:562-76, 2007. • 6. Pitsikas et al., Neuroscience 154: 454-60, 2008.