Bombesin-induced hypothermia and hypophagia are associated with plasma metabolic fuel alterations in the rat.

Microinfusion of bombesin into the preoptic area (POA) has previously been shown to reduce core body temperature and feeding in rats that are food-deprived or made hypoglycemic with insulin. The present study determined the metabolic fuel state of rats under these experimental conditions. In addition, changes in plasma metabolic fuels following the microinfusion of bombesin (50 ng/0.25 microliters) into the POA were evaluated. Rats (n = 8) were tested under conditions of food satiation, food deprivation (20 h), and insulin pretreatment (10 U/kg). Prior to peptide infusion, food-deprived rats exhibited the expected elevation in free fatty acids coupled with a small decline in plasma glucose. Insulin treatment resulted in hypoglycemia which persisted for at least 120 min. Following bombesin infusion, free fatty acids and corticosterone levels were elevated in food-sated rats. Food-deprived rats exhibited elevation in plasma glucose, free fatty acids, and corticosterone following peptide infusion. In insulin-treated rats, bombesin attenuated the hypoglycemia observed in controls and increased corticosterone levels. These findings suggest that bombesin-like peptides localized within the POA may participate in the regulation of metabolic fuels.