Ritanserin overcomes exploratory inhibition induced by cocaine withdrawal

Rats given a subchronic cocaine treatment for 10 days display an inhibition of exploratory behaviour 24h after the last cocaine treatment in the open field test. As compared to the vehicle controls, the exploratory inhibition could be measured in terms of a longer latency to enter the open area, a reduction in the time spent in the open field and a decrease in the number of transits from the small dark compartment into the open area. The serotonin (5-HT(2/1C)) antagonist ritanserin, given subcutaneously 1h prior to testing, overcame this behavioural inhibition. At doses between 0.04mg/kg and 10.0mg/kg ritanserin, a complete normalization of exploratory activity was obtained. In chronic vehicle treated rats, ritanserin did not increase exploration. Therefore the effects of ritanserin cannot be attributed to a general activation. The results are discussed with regard to withdrawal anxiety and a possible therapeutic role of ritanserin in drug addicts.