Effects of phencyclidine-like drugs on responding under multiple fixed ratio, fixed interval schedules

The effects of phencyclidine and a series of related drugs were studied on rates and patterns of responding by rats under a multiple fixed-interval 300s, fixed-ratio 30-response schedule of food presentation. Dizocilipine produced large increases in the rate of FI responding and smaller increases in the rate of FR responding. TCP slightly increased the rate of FI responding and PCE slightly increased the rate of FR responding. Higher doses of all drugs decreased rates of responding under both schedule components with the potency order of dizocilpine > PCE > PCP > TCP > ketamine. This relative potency for decreasing rates of FI and FR responding correlated highly with the affinity of these drugs for PCP receptors, suggesting that the rate decreasing effects of these drugs are mediated through these receptors. An analysis of local rates of responding within the FI suggested that dizocilpine was different from the arylcyclohexylamines in that it was the only drug that increased rates of responding late in the FI component. Previous reports have shown that the ability of arylcyclohexylamines to increase punished responding and to act as discriminative stimuli are correlated highly with binding to PCP receptors. The present experiments suggest that decreases in rates of responding under multiple schedule control are also mediated by PCP receptors.