title: Bombesin-induced hypothermia in rats tested at normal ambient temperatures: contribution of the sympathetic nervous system.
abstract: Rats infused centrally with bombesin become hypothermic at normal ambient temperatures when acutely deprived of food, but not while allowed unrestrained access to food. Ad lib-fed rats, tested at normal ambient temperatures, become hypothermic after receiving intracerebroventricular (ICV) bombesin when they have ventromedial hypothalamic lesions or when administered insulin or 2-deoxy-D-glucose peripherally. All of these conditions have been linked to reductions of sympathetic nervous system activity to brown adipose tissue (BAT), a major thermogenic mechanism of many homeotherms. A between group design was used to examine the effects of ICV bombesin infusions on the response to peripheral injections of a) the sympathetic ganglionic blocker chlorisondamine (2.5 mg/kg, IP) in ad lib-fed rats, b) the nonspecific beta-agonist isoproterenol (30 mg/kg, IP) in food-deprived rats, and c) the combination of isoproterenol and chlorisondamine in ad lib-fed rats. Ad lib-fed rats receiving ICV bombesin (100 ng/5 microliters), in combination with peripheral chlorisondamine injection, became hypothermic 60 min postbombesin administration (-2.84 +/- 0.33 degrees C), while ad lib-fed rats receiving ICV bombesin infusion and peripheral injections of saline did not (-0.08 +/- 0.37 degrees C). Isoproterenol blocked hyperthermia in ad lib-fed rats injected with chlorisondamine and ICV bombesin. Food-derived rats receiving ICV bombesin infusion and peripheral saline injection exhibited hypothermia 60 min postbombesin administration (-2.51 +/- 0.29 degrees C). Peripheral injections of isoproterenol prevented bombesin-induced hypothermia in food-deprived rats. These data suggest that bombesin induces hypothermia at normal ambient temperatures when the sympathetic nervous system drive to BAT cannot be (or is not) activated.
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA.
authors.forename: C
authors.initials: C
authors.lastname: Barton
authors.forename: D A
authors.initials: DA
authors.lastname: York
authors.forename: G A
authors.initials: GA
authors.lastname: Bray
mesh_terms: D002001:Adipose Tissue, Brown / Q000187:drug effects; D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D001839:Bombesin / Q000494:pharmacology*; D002714:Chlorisondamine / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000187:drug effects*; D013696:Temperature
chemical_list: D002714:Chlorisondamine; D007545:Isoproterenol; D001839:Bombesin