A partial reinforcement extinction effect in water-reinforced rats intermittently treated with haloperidol.

Thirsty rats were trained to traverse a straight runway for 30 sec access to water reinforcement. The experiment consisted of daily single trials during a 30-day reinforcement phase followed by 21 days of extinction. Animals that experienced no water reward on 33% of the reinforcement trials subsequently demonstrated an increased resistance to extinction of the runway response compared to continuously reinforced (CRF) animals. This "partial reinforcement extinction effect" (PREE) was also observed in CRF animals pretreated with the neuroleptic drug haloperidol (0.075 or 0.15 mg/kg) on 33% of the reinforcement trials. Thus, periodic dopamine receptor antagonism produced behavioral results comparable to those produced by periodic reward omission. These data cannot easily be accounted for by some form of general drug-induced performance deficit since the extinction trials were conducted in undrugged animals. It was concluded that dopaminergic substrates may play a role in mediating the behavioral effects of water reinforcement.