TYROSINE-HYDROXYLASE, NEUROPEPTIDE-Y, SUBSTANCE-P, CALCITONIN-GENE-RELATED PEPTIDE AND VASOACTIVE-INTESTINAL-PEPTIDE IN NERVES OF RAT PERIOVARIAN ADIPOSE-TISSUE - AN IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL INVESTIGATION

Rat periovarian adipose tissue contains unilocular adipocytes and some multilocular adipocytes that, following acclimation to cold, become m ore numerous and give rise to periovarian brown fat areas. We studied the occurrence and distribution of tyrosine hydroxylase, neuropeptide Y, substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, methionine enkephalin, neurotensin, galanin, and cholecystok inin 9-20 in the nerves of rat periovarian tissue maintained at 20 deg rees C (control rats), acclimated at 4 degrees C (cold-acclimated rats ) and at 28 degrees C (warm-acclimated rats). In the periovarian tissu e of control and warm-acclimated rats, tyrosine hydroxylase-like, neur opeptide Y-like, substance P-like and:calcitonin gene-related peptidel ike immunoreactive elements (putative nerves) were present in the bloo d vessels. In the periovarian tissue of cold-acclimated rats, we found : (1) a more widespread vascular distribution of these neuropeptides; (2) tyrosine hydroxylase-like and calcitonin gene-related peptide-like immunoreactive elements among paucilocular and multilocular adipocyte s (parenchymal-like nerves); (3) vasoactive intestinal peptide-like im munoreactive elements in some arteries. Investigation by EM showed the presence of heterogeneous non-myelinated axons both associated with c apillaries, and among paucilocular and multilocular adipocytes (parenc hymal fibres) in periovarian brown fat areas. In conclusion, periovari an brown fat contains the same neuropeptides, with the same vascular a nd parenchymal distribution, already seen in typical depots of brown f at.