Naloxone-induced suppression of food intake in normal and hypothalamic obese rats.

Intraperitoneal injections of naloxone hydrochloride (1, 2, 4, and 8 mg/kg) suppressed food intake in both normal and hypothalamic obese rats maintained on a 4-hr per day feeding schedule. The decrease in feeding was more pronounced in the animals with ventromedial hypothalamic lesions. Appetitively motivated feeding, i.e., the consumption of sweetened milk under nondeprived conditions, was also suppressed by naloxone, but there was no reliable difference between groups. It is concluded that opiate receptors located in the ventromedial hypothalamus are not essential for the effects of opiate agonists and antagonists on feeding behavior.