Sensitivity to dopamine blocking in rat licking behavior: function of taste stimuli, response difficulty, and...

The behavioral circumstances determining the efficacy of DA blocking was studied by observing the effects of pimozide, tastes and effort required to ingest liquid on consummatory licking responses. The microstructure of ingestive behavior was obtained to delineate differential behavioral adjustments. Twelve water-deprived rats were trained to lick water, 2.00% sucrose, and 0.01% quinine from a spout located either at a down position of 7 cm above (low effort) or an up position of 24 cm above the floor (high effort). They were injected with pimozide (0.25 mg/kg, ip) or its vehicle and licking responses were observed. Results indicated that the pimozide effect was dependent on tastes and positions as well as the behavioral aspects observed. Pimozide affected ingestion of quinine in many ways, but did not affect that of sucrose solution. The position affected ingestion of quinine in more ways than that of sucrose solution. The taste effect of quinine was more complex than that of sucrose. The complex behavioral adjustment to the reduced incentive support with quinine probably rendered the behavior vulnerable to interference by DA blocking and effort requirement.