Blockade of cocaine reinforcement in rats with the dopamine receptor blocker pimozide, but not with the noradrenergic blockers phentolamine or phenoxybenzamine.

31 male Wistar rats self-administering cocaine were treated with the dopamine receptor blocker pimozide or the noradrenergic blockers phentolamine or phenoxybenzamine. Pimozide caused a dose-related (.0625–.5 mg/kg) acceleration of responding; at the higher doses responding subsequently ceased. These effects of pimozide parallel the known effects of reward (unit dose) reduction and reward termination and thus suggest an important role for dopaminergic brain mechanisms in the mediation of cocaine reinforcement. Neither phenoxybenzamine given systemically nor phentolamine given intraventricularly had similar effects; thus no similar role for noradrenergic brain mechanisms is suggested by these experiments. (French summary) (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)