Increased fat consumption induced by morphine administration in rats.

Patterns of caloric intakes and dietary self-selection of the three macronutrients, protein, fat and carbohydrate were examined in male rats following the administration of morphine sulfate (0.0, 1.0, 10.0 and 20.0 mg/kg, IP). Animals were given access to either ground Purina Chow or one of two dietary self-selection regimes, one with a high-fat ration (7.8 kcal/g) and the other with a fat ration isocaloric to the carbohydrate and protein rations (3.8 kcal/g). Animals received morphine injections at the beginning of a six-hour feeding period and nutrient intakes were measured at 1, 2, 4 and 6 hours postinjection. Similar patterns of macronutrient choice were observed for both animals maintained on the high-fat regime and animals with access to the isocaloric components following morphine injections. As a function of morphine injections, animals on both self-selection regimes increased fat intake while suppressing carbohydrate intake and exhibiting little modifications in protein intake.