Carotid body-like tissues around the rat posterior cricoarytenoid muscle.

We examined the carotid body-like tissues around the posterior cricoarytenoid (PCA) muscle of the rat by light and electron microscopy. One branch after bifurcation of the inferior (recurrent) laryngeal nerve frequently formed a small ganglion at the lateral side of this muscle and sometimes contained paraganglion cells (granule-containing cells). In addition, encapsulated structures (paraganglia) enveloped by a few layer of capsular cells were often observed on and near the muscle. Moreover, granule-containing cells resembling the encapsulated paraganglion cells were found in clusters outside the small nerve. These clustered cells were incompletely surrounded by fibroblastic processes. In addition to synapses between adjacent cells, afferent and efferent synapses were distinguished between nerve endings and these cells, possibly receiving both afferent and efferent innervation. These findings suggest that the clustered granule-containing cells outside the small nerve in the proximity of the PCA muscle may function as chemoreceptor cells as well as the paraganglion cells within the nerve bundles and the encapsulated paraganglia.