Dual Adrenergic and Cholinergic Innervation of the Cerebral Arteries of the Rat

Abstract

The innervation of the anterior cerebral artery of the rat was examined by electron microscopy and by the fluorescence method for localizing adrenergic nerves. Two groups of axon bundles were associated with the artery; one at the outer margin of the adventitia (periadventitial bundles) and the other within the adventitia or at the adventitia-media border (adventitial bundles). Periadventitial bundles consisted of nonmyelinated axons (0.1-2µ diam), some of which contained synaptic vesicles; in some bundles, myelinated axons were seen. Adventitial axons often contained many synaptic vesicles and were free of Schwann cell sheath in areas apposed to smooth muscle cells. The closest observed approach of axon to muscle cell was 800 A. No nerve fibers penetrated the medial muscle. After fixation with glutaraldehyde plus osmium, large (1000 A) granular and small (500 A) agranular vesicles were seen within many axon profiles. Small granular vesicles were rare. After permanganate fixation, terminal axons contained...