[Effect of Dextromethorphan on Apomorphine induced licking behavior in rat]

ABSTRACT

Dextromethorphan is a NMDA receptor antagonist in the glutamatergic system. Currently, there are reports showing that the glutamatergic NMDA receptor mechanism stimulates dopamine release from several brain regions. This effect may modulate the stereotyped behaviors of dopaminergic system. The purpose of this study was to determine the interaction between dextromethorphan and stereotyped licking behavior in rats. In the present study, effects of dextromethorphan and different dopamine receptor antagonists on apomorphine-induced licking behavior were examined. For the induction of licking, the dose of 0.5 mg/kg, s.c. of apomorphine was used. Dextromethorphan [10-30 mg/kg, i.p.] dependently reduced the licking behavior. Intraperitoneal injection-of dextromethorphan [15 mg/kg, ED50] potentiated the inhibitory effects of low doses of the dopamine D1 receptor antagonist, SCH 23390 [0.00625 and 0.0125 mg/kg, i.p.] and the dopamine D2 receptor antagonist, pimozide [0.5-1 mg/kg, i.p]. These results suggest that the inhibitory effect of dextromethorphan on apomorphine induced licking behavior is mediated via a doparnine Dl receptor mechanism