Unilaterality of the sympathetic innervation of each pad of rat interscapular brown adipose tissue

Abstract

The effects of sham, unilateral and bilateral surgical denervation of rat interscapular brown adipose tissue (IBAT) on blood flow to the 2 IBAT pads of cold-acclimated (CA) rats during exposure of the animals to 22 or -6.degree. C and on the noradrenaline [norepinephrine] (NA) content and total dopamine-.beta.-hydroxylase (DBH) (EC 1.14.17.1) activity of the pads in both warm-acclimated (WA) rats and CA rats were examined. Increase in IBAT blood flow upon cold exposure was taken as an index of sympathetically mediated calorigenesis in the tissue and decreases in tissue levels of NA and DBH served as indices of the extent of destruction of the sympathetic innervation. At 24 h postsurgery, denervated pads of CA rats, whether from unilaterally or bilaterally denervated IBAT, had < 3% of the NA, 40-44% of the DBH and 0% of the 10-fold, cold-induced increase in blood flow measured in intact pads of CA rats with sham-operated or unilaterally denervated IBAT. IBAT bilaterally denervated for 24 h was as responsive in terms of its maximum increase in blood flow during infusion of CA rats with NA as intact IBAT. DBH in denervated pads of both WA rats and CA rats fell to .ltoreq. 5% of control levels at 2 days postdenervation and remained at these low levels, as did NA, for at least 8 wk. Each pad of rat IBAT apparently was independently innervated by sympathetic fibers.