Effects of dopamine receptor blockade on alimentary behaviors: home cage food consumption, magazine training, operant acquisition, and performance.
Administration of the dopamine receptor blocker pimozide (1.0 mg/kg) disrupted the initiation, but not the maintenance, of home cage food consumption. Likewise, the number of pellets consumed during magazine training was decreased among pimozide-treated rats during the first, but not the second day of training. The acquisition of a bar-press response for food reinforcement (using a retractable bar) was severely retarded by pimozide. However, such an impairment was not evident if animals initially received 2 training days in the absence of the drug. Further, among rats trained to bar press to asymptote using a nonretractable bar, pimozide reduced the within and between days bar-press rate such that performance was indistinguishable from that of animals placed on extinction in the absence of the drug treatment. When transferred from the pimozide treatment to extinction in the absence of drug, the response rate increased to the level observed during the first session of either extinction or pimozide in the continuous reinforcement condition. The results are discussed in terms of sensory-motor and reinforcement consequences of dopamine receptor blockade.