Vena caval bombesin infusion decreases spontaneous meal size in undisturbed rats

The amphibian tetradecapeptide bombesin (BN) decreases food intake in both humans and animals. Studies have typically examined the effects of BN on scheduled meals in deprived subjects. To investigate the properties of this peptide under more naturalistic conditions, we examined the effects of BN in spontaneously feeding rats. Undisturbed, ad lib-fed male rats (n = 9) with chronic inferior vena caval catheters were infused with saline vehicle and each of 3 doses (2, 4, and 8 micrograms/kg) of BN in counterbalanced order with intervening noninfusion days. Infusions were remotely activated at the onset of the first nocturnal meal and continued for 3 min (34 microliters/min), delivery being completed within the first 2 min of infusion. Feeding was measured via electronic balances linked to a computer. All doses of the peptide significantly decreased the size and duration of the first nocturnal meal. In addition, 4 and 8 micrograms/kg of BN significantly shortened the intermeal interval from the end of the first meal to the beginning of the second meal. Despite this, the satiety ratio (interval/meal size) tended to increase after BN and was significantly increased by the highest dose (8 micrograms/kg), thus indicating a sustained satiety action of the peptide. In summary, these results show that brief, meal-contingent intravenous infusions of BN potently inhibit spontaneous feeding in undisturbed rats.