Effects of β-funaltrexamine on ingestive behaviors in the rat

Abstract

The effects of β-funaltrexamine (β-FNA), an irreversible μ-opioid receptor antagonist, were determined on water and food intake of non-deprived rats. Intracerebroventricular administration of 1.25 or 2.5 μg of β-FNA did not affect drinking or eating. However, 5.0 μg first transiently increased food intake and then reduced both water and food intake for at least 72 h. Locomotor activity was unaffected by 5.0 μg of β-FNA; thus, changes in ingestive behavior were not a secondary consequence of drug-induced behavioral stimulation or depression. The early increase in food intake may be due to the short lived and reversible κ-agonist activity of β-FNA. On the other hand, selective blockade of μ-opioid receptors appears sufficient to reduce the intake of water and food.