Involvement of sympathetic activation and brown adipose tissue in calcitonin gene-related peptide-induced heat production in the rat

Abstract

We previously reported that microinjection of calcitonin gene-related peptide (CGRP; 1.6–8.0 pmol, 0.2–1.0 μl) into the ventromedial hypothalamus (VMH) increased oxygen consumption ( VO 2), heart rate (HR), colonic temperature ( T co), and temperature of interscapular brown adipose tissue ( T IBAT). In the present study, we investigated whether the autonomic nervous system is involved in the CGRP-induced heat production in urethane-anesthetized rats. Intraperitoneal administration of the ganglion blocker hexamethonium (20 mg/kg) or the β-adrenergic antagonist propranolol (5 mg/kg) suppressed the CGRP-induced increases in VO 2, HR, T co, and T IBAT. Pretreatment with the α-adrenergic antagonist phentolamine (5 mg/kg) partly attenuated the heat production response but did not affect the tachycardiac response. Bilateral sectioning of the nerves supplying the IBAT attenuated the CGRP-induced increase in T IBAT but not significantly that in VO 2 or T co. In rats with adrenal demedullation, the effects of CGRP were similar to those in intact rats. These results suggest that the CGRP-induced heat production is mediated by the sympathetic nervous system and, at least in part, by the BAT through the α- and β-adrenoceptors.