Suppression of nocturnal, palatable and glucoprivic intake in rats by the kappa opioid antagonist, nor-binaltorphamine.

The increased food intake in the rat during the first two hours of the dark cycle was significantly inhibited by central pretreatment with either the selective kappa opioid antagonist, nor-binaltorphamine (NorBNI, 20 micrograms, i.c.v., 53-54%) or naltrexone (NTX, 20 micrograms, i.c.v., 47-60%). Short-term (2 h) intake of a high-fat diet was significantly inhibited by central NorBNI (1-20 micrograms, 33-79%) and NTX (20 micrograms, 47-51%). Hyperphagia induced by the anti-metabolic glucose analogue, 2-deoxy-D-glucose was significantly inhibited by central NorBNI (20 micrograms, 40-68%) and NTX (20 micrograms, 28-69%). These data suggest that the kappa receptor subtype, in addition to other opioid receptor subtypes, influence these forms of feeding behavior.