Failure of naloxone to attenuate fasting induced hyperphagia in broiler chicks.

Subcutaneous administration of naloxone at 1 to 10 mg/kg produced a dose-related decrease in feed intake of broiler chicks. Food deprivation for 3, 6, 12, and 24 hours produced a significant increase in feed intake compared to non-food deprived birds. Subcutaneous administration of naloxone at 1 to 10 mg/kg failed to attenuate hyperphagia of broiler chicks, deprived of food for 12 hrs. These data suggest that opiate receptors are involved in the regulation of spontaneous feeding behavior in broiler chicks. However, in contrast to other mammals and pigeons, a mechanism, other than endorphinergic system, not sensitive to naloxone blockade, might be involved in food deprivation induced hyperphagia in broiler chicks.