Hypoinsulinemia may mediate the lowering of self-stimulation thresholds by food restriction and streptozotocin-induced diabetes.

7 days beyond cessation of insulin treatment) elevation of threshold in ad libitum fed rats and, more transiently, reversed the threshold-lowering effect of food restriction. Acute insulin treatment (3 mU, 15 min prior) also elevated threshold in food-restricted rats. These results are consistent with the hypothesis that insulin modulates sensitivity of a brain reward system and that hypoinsulinemia may be the common factor in food restriction and diabetes that accounts for the enhancement of perifornical LHSS.