Effect of Sarcosine (a Glycine Transport 1 Inhibitor) and Risperidone (an Atypical antipsychotic Drug) on MK-801 Induced Learning and Memory Deficits in Rats.

Abstract

The present study was carried out to evaluate whether the combined administration of sarcosine with risperidone possess any advantageous effects on dopaminergic and NMDA receptor-mediated glutamatergic neurotransmissions as compared to single drug administration in rats. The Wistar rats were divided into 7 groups each with different treatments. MK-801 (0.1 mg/kg, i.p.) was injected as single dose on 14th day for inducing learning and memory deficits in animals. Sarcosine (300 and 600 mg/kg, i.p.) and risperidone (0.2 mg/kg, i.p.) were administered daily for 14 days. Spatial habituation learning and hole board tests were performed on 14th day followed by measurement of GABA and 5-HT levels in brain tissues of rats. Pretreatment of sarcosine (600 mg/kg, i.p.) non-significantly improved learning and memory deficits induced by non-competitive NMDA receptor antagonist MK-801, significantly increased the GABA and decreased the 5-HT levels (p<0.05). Combined administration of sarcosine (300 mg/kg, i.p.) with risperidone (0.1 mg/kg, i.p.) synergistically improved cognitive deficits significantly, decreased % errors in hole board learning test, and increased centre time, corner time in spatial habituation learning test (p<0.05). The combined administration also potentiated the GABA and decreased 5-HT levels, indicating that the increased synaptic glycine concentrations may enhance NMDA receptor function which is directly linked with increased GABAergic transmission in striatum region and decreased 5-HT levels showed antagonistic action hence, enhancing the cognition. Our results suggest that combined administration of sarcosine with risperidone may strengthen glutamatergic tone in striatum. Thus, it may be a novel regime to improve psychotic symptoms and cognitive deficit in schizophrenia.