Ureteric vascular and muscle coat innervation in the rat. A quantitative ultrastructural study.

The application of a quantitative ultrastructural approach to the study of the innervation of the smooth muscle in the wall of the ureter of the rat has revealed major differences in the structure of the nerves in the muscle coat and in the walls of the arterioles. The high density of adrenergic terminals in the periarteriolar nerves is consistent with the distribution of many of the postganglionic sympathetic axons that run in the ureteric nerves to blood vessels and the low density of both adrenergic and cholinergic terminals in the intramuscular nerves implies that the autonomic nervous system plays only a secondary role in controlling the activity of the muscle. The mean size of the intramuscular nerves corresponds to that of the nerves in the submucosa and terminals of the kind that occur in the submucosal nerves are numerous. The function of axons with such terminals and their possible involvement in the transmission to the central nervous system of pain impulses is discussed.