Nor-binaltorphimine decreases deprivation and opioid-induced feeding

We evaluated the effect of the κ antagonist, nor-binaltorphimine (nor-BNI) on deprivation and opioid-induced feeding in rats. Intracerebroventricular administration of nor-BNI (100 nmol) decreased deprivation-induced feeding for as long as 24 h, albeit in a fairly weak manner (maximum decrease of ≈28%). Nor-BNI (1, 10 and 100 nmol) decreased feeding induced by the κ ligand U-50,488H by as much as 85% during the first hour of the study. This κ antagonist also decreased feeding induced by the σ agonist DSLET and the μ agonist DAMGO. Based on previous studies indicating that nor-BNI is a selective κ antagonist, we conclude that not only U-50,488H (κ), but also DSLET (σ) and DAMGO (μ)-induced feeding are dependent upon an active κ receptor.