Conditioning of insulin-induced hyperphagia

8 Sprague-Dawley rats which had a history of insulin administration prior to assessment of food-reinforced operant performance demonstrated insulin-like high response rates when subsequently injected with a physiological saline placebo, confirming previous reports. Results obtained from additional groups suggest that this finding did not reflect the classical conditioning of hunger. Rather, the relevant effect of the insulin training sessions may have taught S an instrumental response which was reinforced by decreases in insulin-induced distress, and it was this instrumental response, rather than the motivational state, that was elicited by the placebo.