Abstract
We employed light and electron microscopy to examine the innervation of terminal arterioles in the rat posterior cricoarytenoid (PCA) muscle over a three-week period before and after unilateral denervation of the recurrent nerve. Observations showed an occasional single small-sized myelinated nerve fiber around the terminal arteriole in both normal and denervated PCA muscles. One axon after the last node of Ranvier of the small-sized myelinated nerve fiber, together with some nonmyelinated nerve fibers, was enwrapped by the Schwann cell and ran along the terminal arteriole, forming varicose swellings with numerous mitochondria along its course. In one instance, a small-sized myelinated nerve fiber in the denervated PCA muscle ramified into several branches containing numerous mitochondria. These nerve endings mainly existed in the adventitia, consisting of some layers of fibroblasts and collagen fibrils, and some of them were close to the vascular smooth muscle cells with only an intervening basal lamina. These findings suggest that the mitochondria-filled nerve endings may be sensory in nature, and function in response to the expansion and contraction of blood vessels caused by increased and/or decreased blood flow or intravascular pressure.
