The effect of phencyclidine and ketamine on schedule-controlled behavior in the pigeon.

Pigeons were trained under a multiple schedule of food presentation with alternating 30-response fixed-ratio (FR-30) and 10-minute fixed-interval (FI-10) components. Average rates of responding were 2.9 and 0.55 responses/sec, respectively. Both phencyclidine (0.03-3.0 mg/kg i.m.) and ketamine (0.1-30.0 mg/kg i.m.) increased response rates at low doses while decreasing response rates at high doses during the FI-10 component. Only a dose-related decrease in response rates was seen in the FR-30 component with both phencyclidine and ketamine. In individual birds, the maximum rate increases in the FI-10 component ranged from 110% to 163% of the control rate. The rate increases in the FI-10 component depended on the control rate of responding. The effects of phencyclidine and ketamine were qualitatively similar to d-amphetamine (0.1-10 mg/kg i.m.).