Ultrastructural identification of non-adrenergic,non-cholinergic nerves in the rat anococcygeus muscle

The innervation of the rat anococcygeus muscle has been investigated ultrastructurally following fixation with a modified chromaffin reaction for the demonstration of biogenic amines (Tranzer and Richards, 1976). Three types of nerve profiles were revealed: (1) 60-70% of the profiles are adrenergic; (2) less than 5% of the profiles appear to be cholinergic; (3) up to 40% of the profiles are distinguished by the presence of a characteristically high proportion of electron-opaque, chromaffin-negative vesicles, 85-110 nm in diameter. This third type of profile was not affected by 6-OHDA, and is considered to represent the non-adrenergic, non-cholinergic inhibitory innervation of this tissue. Because of the morphological similarity of this nerve type, apart from the smaller vesicle size, to classical peptidergic nerve endings, they have been termed "small p-type" (sp-type). These results are discussed in relation to a previous report describing only two types of nerve profiles in this tissue (Gillespie and Lüllmann-Rauch, 1974).     

Occurrence of uranaffin-positive synaptic vesicles in both adrenergic and non-adrenergic nerves of the rat anococcygeus muscle

Summary The uranaffin reaction in rat anococcygeus muscle, which receives a dual innervation of both adrenergic and non-cholinergic, non-adrenergic nerves was examined. Dense reaction product was observed in the vesicular membranes and/or the cores of some synaptic vesicles in the adrenergic nerve terminals. Occasional vesicles were filled up with dense reaction product. In the prominent population of small clear vesicles, however, no dense reaction product was observed. The number of small granular vesicles in the adrenergic nerve terminals was markedly increased after the administration of 5-hydroxydopamine (5-OHDA). These granular vesicles were moderately stained with uranaffin deposit on the cores but their limiting membranes possessed no uranaffin deposit at all.In the non-adrenergic nerve terminals, on the other hand, uranaffin deposit of variable density was observed on the cores of large granular vesicles but never on their limiting membranes or on the small clear vesicles. There was no change in the axon profiles after the administration of 5-OHDA.The possible occurrence of purines in the cores of large granular vesicles in the non-adrenergic nerves is discussed.     

Innervation of the anococcygeus muscle of the rat

Summary The innervation of the anococcygeus muscle of the rat was investigated with regard to the histochemical features of nerve fibers within the muscle and to the location of the postganglionic autonomic neurons which are the source of these fibers. Acetylcholinesterase-positive fibers and catecholaminergic fibers are abundant in the anococcygeus as well as the related retractor penis muscle. Neuronal somata, either between muscle bundles of the anococcygeus or in the connective tissue sheath, are also acetylcholinesterase-positive. Nerve fibers and a minority of the ganglion cells in the anococcygeus and retractor penis muscles are immunoreactive for vasoactive intestinal polypeptide. Injection of the retrogradely transported dye Fluorogold into the anococcygeus muscle filled neurons in the abdominopelvic sympathetic chain, pelvic plexus and a small number of neurons in the inferior mesenteric ganglion. In the pelvic plexus, some neurons were located in the major pelvic ganglion but most were found along the main penile nerve and its branches to the anococcygeus muscle. Immunocytochemistry of these identified neurons indicates that about one half of them are positive for vasoactive intestinal polypeptice. These results raise the possibility that both acetylcholine and vasoactive intestinal polypeptide are important neurotransmitters in autonomic nerves to the anococcygeus muscle.