Naltrexone suppresses hyperphagia induced in the rat by a highly palatable diet.

A highly palatable diet (ordinary chow supplemented with 4 highly palatable items changes every day) (HPD) provokes hyperphagia and overweight in the rat. After 17 weeks of such a diet, naltrexone (0.5 or 2.5 mg/kg IP) and opiate antagonist, was injected at the beginning of the dark period, and a food intake test was performed during the 3 following hours. Naltrexone does not modify the energy intake in control rats receiving ordinary chow but suppresses HPD induced hyperphagia. The involvement of the beta-endorphin system in this type of hyperphagia is discussed.