The innervation of the rabbit ear artery. An ultrastructural study

An examination of sections of the central artery of the rabbit external ear with the transmission electron microscope revealed a single and uniform population of axons near the medial-adventitial border. The dimensions of the neuromuscular cleft (mean closest distance 0.5 micrometer) and of the approaches between smooth muscle cells (not less than 20 nm) were determined. On the basis of the morphology of the neuronal vesicles and their ability to take up 5-hydroxydopamine the axons were classified as adrenergic, confirming previous light-microscopic histochemical observations. The axons also exhibited a weak but definite acetylcholinesterase activity in association with their sxon membrane, as shown by a histochemical technique.