Ultrastructural and morphometric studies on the peripheral course of the vagus in the domestic fowl, with particular reference to the cholinergic innervation of the pancreas.

Cytochemical and morphometric studies were carried out to ascertain the peripheral course of the vagus nerve to the chicken pancreas. Nerve bundles accompanying the left gastric artery were named tentatively the left gastric artery nerve which contained unmyelinated and myelinated nerve fibers showing the acetylcholinesterase positive reaction. After vagotomy various degenerating features were observed in both the unmyelinated and myelinated nerve fibers of the left gastric artery nerve. The ratio of unmyelinated nerve fibers to myelinated nerve fibers decreased significantly following vagotomy, whereas there was no significant difference in the total number of myelinated nerve fibers between the control and vagotomized chickens. Thus, it is hypothesized that the total number of unmyelinated nerve fibers decreases significantly following vagotomy. Our studies yielded the evidence that the left gastric artery nerve contains the unmyelinated nerve fibers derived from the vagus nerve. Moreover, the coeliac plexus showed no significant change in the ratio of unmyelinated to myelinated nerve fibers nor signs of degeneration following vagotomy, although both were observed in the nerve bundles accompanying the pancreatico-duodenal artery. It is, therefore, concluded that a peripheral branch of the vagus nerve runs together with the left gastric and the pancreatico-duodenal arteries, and must innervate the pancreas as the preganglionic nerve fiber.