NALOXONE BLOCKS THAT PORTION OF FEEDING DRIVEN BY SWEET TASTE IN FOOD-RESTRICTED RATS

We evaluated the potency of naloxone on intake of normal and sweet cho w in food-deprived and schedule-fed rats. We found that naloxone's ano rectic potency was dependent on the type of chow presented to the rats and the deprivation schedule utilized to stimulate food intake. In 24 -h and 48-h deprived rats, naloxone decreased intake of normal rat cho w at doses ranging from 0.3 to 3 mg/kg. In chronically deprived rats ( 80% of normal body wt), these doses of naloxone failed to decrease int ake of normal chow. Rats eating sweet chow ate more when energy depriv ed and were more sensitive than rats eating normal chow to naloxone-in duced limitations in food intake, both in acute and chronic food-depri ved groups. Thus naloxone decreased intake of sweet chow much more eff ectively than normal chow even when rats were chronically food deprive d. We also found that an extremely low dose of naloxone (0.03 mg/kg) d ecreased intake of sweet chow by almost 50% in satiated rats.