Barton C, York DA, Bray GA. Bombesin-induced hypothermia in rats tested at normal ambient temperatures: contribution of the sympathetic nervous system.
Brain Res Bull 1995;
37:163-8. [PMID:
7606492 DOI:
10.1016/0361-9230(94)00272-3]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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.
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