Failure of ritanserin to block the discriminative or reinforcing stimulus effects of cocaine.

Ritanserin, a 5-HT2/1C antagonist, has been suggested to reduce the preference for cocaine in rats. In the present experiment, the action of ritanserin was investigated in locomotor activity, cocaine drug discrimination, and cocaine self-administration paradigms in rats. A low dose of ritanserin (1.0 mg/kg) was without effect on locomotor activity, while a higher dose (10.0 mg/kg) reduced both horizontal and vertical locomotor activity counts during the first 30 min of the test session. Ritanserin (0.32-32 mg/kg) did not significantly affect the discrimination of 10 mg/kg of cocaine, nor did a dose of 10.0 mg/kg significantly modify the dose-effect curve for cocaine discrimination. Ritanserin (1.0 and 10.0 mg/kg) had no significant effect on the dose-response curve for cocaine self-administration. Thus, ritanserin was without effect against either the discriminative or reinforcing stimulus effects of cocaine, suggesting that ritanserin has limited efficacy as a potential treatment for cocaine abuse.