Behavioral effects of chronic phencyclidine in monkeys.

Phencyclidine (PCP) and other NMDA receptor antagonists such as ketamine induce psychotic symptoms that are difficult to reverse with current medications and which closely resemble those of schizophrenia. This study investigated the behavioral effects of continuous PCP administration in six socially-housed Cebus apella monkeys. Chronic treatment was associated with a sustained decrease in stereotyped locomotion (pacing) and a sustained increase in scanning behavior. Treatment was also associated with a modest decrease in self- and environment-directed behavior and goal-directed locomotion and an increase in affiliative behavior at lower doses. Four animals had one or more episodes of extreme motoric and physiological responses precipitated by stressful events. The results indicate that behavioral effects of chronic PCP in primates differ from those seen following acute treatments and represent an appropriate model system for new antipsychotic drug development.