The effects of intramuscular injections of chlorpromazine were studied in rhesus monkeys whose lever-press responding was maintained under a second-order fixed-interval, fixed-ratio schedule of food (300 mg) or cocaine (0.01 - 0.3 mg/kg/injection) reinforcement. When the dose per injection of cocaine was small (0.01 - 0.03 mg/kg), chlorpromazine produced similar dose-related decreases in responding maintained by either cocaine or food. As the dose of cocaine that maintained behavior was increased, the effects of chlorpromazine were correspondingly attenuated, suggesting a dose-related antagonism by self-injected cocaine of the rate-decreasing effects of chlorpromazine. When high doses of cocaine (0.1 - 0.3 mg/kg/injection) maintained responding, chlorpromazine reversed, to some extent, the changes in the rate and pattern of responding produced by self-injected cocaine. For example, when self-injections of high doses of cocaine induced relatively low rates of behavior, clorpromazine increased cocaine-reinforced responding. An analysis of the effects of chlorpromazine on response rates in successive segments of the fixed interval revealed that the ability of the drug to increase low rates of responding maintained by cocaine could not be attributed solely to the rate-dependent effects of chlorpromazine. The behavioral effects of combinations of cocaine and chlorpromazine appear to involve a reciprocal antagonism of the rate-modifying effects of the drugs.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Jan 1 1980|
ASJC Scopus subject areas
- Molecular Medicine