BUTORPHANOL INCREASES FOOD-REINFORCED OPERANT RESPONDING IN SATIATED RATS

In the present series of studies we examined the effect of butorphanol tartrate on food-reinforced operant responding in satiated rats. In t he first experiment, 8.0 mg/kg butorphanol was administered subcutaneo usly, once per day for 4 days, to satiated rats responding under an fi xed ratio 10 (FR 10) reinforcement schedule. In the second experiment, butorphanol (0, 0.3, 1.0, 3.0, 10.0 mg/kg) was administered to satiat ed rats responding under an FR 80 (first pellet) FR 3 (subsequent pell ets) reinforcement schedule for 4 consecutive days. Repeated butorphan ol administration increased total amount of food consumed over session s in both experiments. Under the FR 80 schedule component, butorphanol initially increased latency to acquire the first pellet, an effect at tenuated by repeated administration. Whereas vehicle administration wa s associated with consumption of relatively large quantities of food w ithin the first 10 min of receiving the first pellet, butorphanol was associated with continued feeding as the session progressed. These dat a suggest that butorphanol-induced food intake is associated with main tenance rather than initiation of feeding.