MEAL PATTERN-ANALYSIS IN RATS REVEALS PARTIAL AGONIST ACTIVITY OF THEBOMBESIN RECEPTOR ANTAGONIST BW2258U89

The spontaneous feeding behavior of adult male rats was monitored duri ng continuous infusion of the bombesin receptor antagonist BW2258U89 i nto the coeliac artery (100 mu g kg(-1) h(-1)) from an osmotic minipum p. Nocturnal food intake was suppressed over 5 days of testing. Simila r effects followed acute BW2258U89 treatment 100 pg kg(-1), intraperi toneally (IP). Moreover, IP BW2258U89 mimicked the acute behavioral e ffects of 2 mu g kg(-1) IP bombesin by reducing meal size. Verifying t hat BW2258U89 can retain its potency throughout the entire period of c hronic infusion, we demonstrated that the acute anorectic action of bo mbesin (4 mu g kg(-1), IP) was blocked by pretreatment with a BW2258U8 9 solution (100 mu g ml(-1) kg(-1), IP) that was freshly prepared, or incubated for 1 or 6 days at body temperature. These data demonstrate that acute and chronic administration of BW2258U89, at a dose that abo lishes the satiety effect of bombesin, significantly suppresses sponta neous feeding. Thus, BW2258U89 appears to attenuate food intake by act ing as a partial agonist at peripheral receptors for bombesin-like pep tides.