EFFECTS OF PHENCYCLIDINE AND DIZOCILPINE ON NMDA-INDUCED, KAINATE-INDUCED AND WATER DEPRIVATION-INDUCED DRINKING IN PIGEONS

The excitatory amino acid (EAA) agonists, N-methyl-D-aspartate (NMDA) and kainate, elicit a copious drinking response in pigeons. NMDA-induc ed drinking, as compared with kainate- and water deprivation-induced d rinking, is selectively antagonized by the competitive NMDA receptor a ntagonist CGS 19755, and appears to be mediated by NMDA receptors loca ted in brain. There have been several studies which have reported diff erences between competitive and non-competitive (PCP-like) NMDA antago nists in blocking various behavioral effects of NMDA, such as discrimi native stimulus effects. The present studies examined the effects of t he non-competitive antagonists, phencyclidine (PCP) and dizocilpine, o n drinking elicited by NMDA, kainate, and water deprivation. PCP and d izocilpine were effective antagonists of NMDA-induced drinking, result ing in surmountable shifts to the right in agonist dose-response funct ions. These compounds had little effect on drinking evoked by either k ainate or water deprivation. These results support the notion that the dipsogenic effects of NMDA are mediated by NMDA-type receptors, and a lso provide important information as to the characteristics of non-com petitive NMDA antagonists. EAA-induced drinking provides a useful tool for the examination of the behavioral pharmacology of EAA agonists an d antagonists.