Cardiovascular effects of cocaine during operant cocaine self-administration.

The aim of this study was to investigate the acute and chronic effects of cocaine self-administration behavior on cardiovascular function. Mean blood pressure and heart rate were measured by radio-telemetry during several experimental conditions. Initial control studies eliminated possible confounds related to the effects of saline injections and operant responding on heart rate and blood pressure. When rats were first allowed to self-administer 0.5-mg/kg injections of cocaine (FR(fixed ratio)10:TO 30 s), there was a significant increase in blood pressure. Tolerance developed to this effect within 3 daily sessions. A significant decrease in blood pressure and heart rate was observed during saline-substitution sessions. Increasing the injection dose of cocaine (1.0, 2.0 and 4.0 mg/kg per injection) did not produce a dramatic increase in blood pressure or heart rate despite significant cumulative cocaine intake (20-27 mg/kg). The cardiovascular effects of cocaine administration did not approach magnitudes previously reported. The results of the current study suggest that operant-conditioned behaviour and/or the direct reinforcing effects of cocaine modulates the cardiovascular effects of cocaine.