Neuropeptides in interscapular and perirenal brown adipose tissue in the rat: a plurality of innervation.

ABSTRACT

The occurrence of neuropeptides in rat brown adipose tissue has been investigated. Immunohistochemical studies on interscapular and perirenal brown fat have demonstrated unequivocally the presence of substance-P (SP)-like, neuropeptide-Y (NPY)-like and calcitonin gene related-peptide (CGRP)-like immunoreactive elements (putative nerves) in adventitial distribution on inter- and intralobular supply arteries and in accompanying nerve bundles. At a more peripheral level, some NPY-like immunoreactive elements and a greater number of CGRP-like immunoreactive elements were observed in the parenchymal field. Somatostatin, bombesin, neurotensin, enkephalin, and vasoactive-intestinal-polypeptide immunoreactivities were not detected. No differences in neuropeptide distribution were noted between interscapular and perirenal brown fat. There is a degree of coincident distribution of SP, NPY and CGRP with that of noradrenergic nervous elements as visualized by condensation histochemistry. Since after 6-hydroxydopamine treatment not all the nerve terminals in rat brown adipose tissue are stigmatized (earlier report), the present results have been discussed in the light of a possible pluralism in innervation of brown adipose tissue.