Sympathetic control of glucagon receptor mRNA levels in brown adipose tissue of cold-exposed rats

Brown adipose tissue (BAT) is implicated in both cold-induced thermogenesis and regulation of energy expenditure and is mainly controlled by sympathet ic innervation. To clarify the permissive and/or complementary roles of glu cagon in cold-induced BAT activation, glucagon receptor gene expression and its modulation by sympathetic activity were investigated in rats. One pad of interscapular BAT was surgically denervated while the other pad was sham operated, then rats were either cold-exposed (CE) for 1 week at 4 degrees C or kept near thermoneutrality (25 degrees C, TN). Using a semi-quantitati ve reverse transcriptase-polymerase chain reaction (RT-PCR) assay, it was s hown that cold exposure decreased (-44%) the relative abundance of BAT gluc agon receptor mRNA, an effect which was prevented by unilateral surgical sy mpathectomy of BAT. The present results show a negative control by sympathe tic nervous activity of glucagon receptor gene expression and/or of glucago n receptor mRNA stability in BAT of cold-exposed rats. The down-regulation of glucagon receptor expression during cold exposure does not support a maj or role of the peptide in the thermogenic control of BAT.