EFFECTS OF HALOPERIDOL IN A RESPONSE-REINSTATEMENT MODEL OF HEROIN RELAPSE

The present study employed an animal model of drug relapse in which pr eviously extinguished heroin self-administration behavior was reinstat ed following a single reinforced trial. Male albino rats were trained to traverse a straight-alley for a reinforcer consisting of a single I V injection of 0.06 mg/kg diacetylmorphine (heroin). Once the alley-ru nning had been established, the heroin reinforcer was removed and the operant behavior permitted to extinguish over trials. On treatment day , animals were injected 45 min prior to testing with 0.0, 0.075, 0.10, 0.15 or 0.3 mg/kg of the dopamine receptor antagonist, haloperidol. A single trial was then conducted during which some animals continued t o experience extinction conditions while others were injected with the heroin reinforcer upon entry into the goal box. The effects of these manipulations were determined during an additional single test trial c onducted 24 h later when the subjects were no longer drugged. While he roin produced a reliable reinstatement in operant responding, this eff ect was dose-dependently prevented by pretreatment with haloperidol. T hese data suggest that dopamine receptor antagonism alters the reinfor cing consequences of heroin administration as measured by heroin's abi lity to reinstate operant behavior following a prolonged period of non reinforced responding.