Interscapular Location of Brown Adipose Tissue: Role in Noradrenaline-Induced Calorigenesis in Cold-Acclimated Rats

Abstract

Tying Sulzer's vein does not alter the enhanced metabolic response to noradrenaline of cold-acclimated rats, neither immediately after the operation nor 1, 2, or 5 days later. In contrast, removal of the interscapular brown adipose tissue, while having no marked immediate effect upon the enhanced metabolic response to noradrenaline, causes a delayed loss of the enhancement during the subsequent 2 days. These findings argue against the hypothesis that the local direction of heat from the interscapular brown adipose tissue via Sulzer's vein to the spinal cord has importance in determining the capacity of the rat to respond to noradrenaline or to use nonshivering thermogenesis. The difference between the effect of complete removal of the interscapular brown adipose tissue and the effect of tying Sulzer's vein would suggest that the reduced circulation through the interscapular brown adipose tissue when Sulzer's vein is tied is still sufficient for it to exert its influence upon other tissues. The results are compatible with the endocrine hypothesis for the function of the interscapular brown adipose tissue during acclimation to cold.