CALCIUM-CHANNEL BLOCKERS ANTAGONIZE SOME OF COCAINE CARDIOVASCULAR EFFECTS, BUT FAIL TO ALTER COCAINE BEHAVIORAL-EFFECTS

The effects of cocaine alone and in combination with the calcium chann el blockers nimodipine, verapamil and diltiazem were determined for di fferent groups of squirrel monkeys on cardiovascular function, schedul e-controlled behavior and drug self-administration. Cocaine alone (0.3 mg/kg) produced increases in both blood pressure and heart rate. All three calcium channel blockers antagonized the presser effect, but wer e ineffective against the tachycardiac effect of cocaine. Nimodipine w as the most potent agent in antagonizing the presser effect of cocaine . Response rates for monkeys responding on a second-order schedule of food presentation were increased by intermediate doses of cocaine (0.1 -1.0 mg/kg) and were primarily decreased at a higher dose (3.0 mg/kg). Quarter-life values, an index of response patterning, were only decre ased by cocaine. None of the calcium channel blockers altered cocaine' s effects on either response rate or response patterning. In the self- administration experiments, the training dose of 56 mu g/kg cocaine ma intained high rates of responding on a simple fixed-ratio schedule. As with schedule-controlled behavior, none of the calcium channel blocke rs altered cocaine self-administration even when administered before s erf-administration sessions during 5 consecutive days. These results s uggest that the calcium channel blockers may be useful in treating car diovascular-retated complications after cocaine use, but they would no t be effective as long-term treatment agents for cocaine abuse.