A putative multipartite model of haloperidol interaction in apomorphine-disturbed behavior of the dog.

The interaction between various doses of apomorphine and haloperidol on intracranial self-stimulation in the dog was studied using a pradigm in which reinforcing brain-stimulation was controlled by a discriminative auditory stimulus. Reinforced lever-pressing was decreased by low doses of apomorphine and completely suppressed by stereotypogenic doses. At various doses of apomorphine, low doses of haloperidol either increased response inhibition by enhancing stereotypy, or increased lever pressing by reducing stereotypy while concomitantly increasing the number of nonreinforced responses. Intermediate to relatively high doses of haloperidol antagonized stereotypy and the response inhibition produced by apomorphine. High doses of haloperidol antagonized stereotypy but also suppressed self-stimulation. Thus, haloperidol is not only able to restore performance capability, but also disturbed reinforcing and discriminative stimulus control.