Naloxone attenuates food but not water intake in Japanese quail.

The effect of the opioid antagonist naloxone on food and water intake in male Japanese quail (Coturnix coturnix japonica) was investigated. Birds were injected intramuscularly with 0, 3, 10, and 30 mg/kg body weight of naloxone hydrochloride. Food and water were offered ad libitum 15 min postinjection. Food intake was attenuated in a dose-dependent fashion through 300 min following the return of food and water. The dose-response relationship was quadratic, with the greatest reduction in food intake occurring at the 10 mg/kg body weight dose. Water intake was not affected by naloxone. The results demonstrate that endogenous opioid peptides are involved in the regulation of food, but not water, intake in Japanese quail.