ORAL-MOVEMENT PATTERNS INDUCED IN RATS BY LOCAL INFUSIONS INTO STRIATUM DEPEND UPON THE REGIMEN OF PRIOR NEUROLEPTIC EXPOSURE

Rats were pretreated for 11 months with vehicle or with chronic halope ridol (HAL), administered either continuously (in the drinking water) or intermittently (via weekly injections). During this time the animal s were habituated to an enclosed tube and periodically monitored by a computerized video device which measured their oral movements. The rat s were then withdrawn from chronic HAL and bilateral cannulae were imp lanted in the ventrolateral striatum (VLS) and substantia nigra (SN). One week lateral oral movements were observed in an open cage and then measured by the computerized video device following bilateral infusio ns into VLS of the muscarinic agonist pilocarpine or the dopamine D-1 agonist SKF38393, or following infusions of the GABA antagonist bicucu lline into SN. Agonist infusions into VLS had different effects depend ing upon the prior regimen of chronic HAL. Infusion of pilocarpine int o VLS led to an exaggeration of the distinctive oral movement form whi ch follows continuous HAL but an attenuation of the different oral syn drome in the intermittent chronic HAL animals. Infusions of SKF38393 i nto VLS had similar, but considerably smaller effects. Infusions of bi cuculline into SN did not induce either effect. These results indicate differences exist in either striatum or its output circuitry in the n eurochemical mechanisms which mediate the different oral movement form s induced by different chronic neuroleptic regimens.