Innervation of bovine mesenteric lymphatics: From the histochemical point of view

Abstract

Histochemical studies were carried out on the distribution of adrenergic and cholinergic nerves in bovine mesenteric lymphatics. Most of the catecholamine-specific fluorescent nerve fibers demonstrated by the glyoxylic acid method encircled these vessels, although a few of them ran spirally or longitudinally. The fluorescent nerve fibers were present not only in the adventitia but also in the smooth muscle layers. The peak wavelengths of excitation and emission spectra of the fluorescence analyzed by means of a microepifluorescence spectrophotometer were about 415 and 465 nm, respectively. Both the values agreed with those of norepinephrine. Most of the cholinesterase-positive fibers stained by the copper thiocholine method were longitudinal in direction. The pattern of their distribution was similar to that of the catecholamine-containing nerve fibers, though the distribution density of the former fibers was less than the latter. Labeling was not affected by 10 −4 M iso-OMPA in the presence of acetylthiocholine iodide as a substrate—an indication that the staining of these fibers is specific for cholinesterase activity. These results suggest that the adrenergic and cholinergic nerve fibers are distributed in the smooth muscle layers as well as in the adventitia of bovine mesenteric lymphatics.