Abstract
Morphological characteristics in the carotid bodies of spontaneously hypertensive rats (SHR) and those of age-matched normotensive Wistar rats (NWR) as well as age-matched genetically comparable Wistar rats (WKY) were examined. The distribution and abundance of four different regulatory neuropeptides, substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) in the carotid bodies of three strains of rat were also examined. The carotid bodies of SHR were greater than those of NWR and WKY. The values in the long axis of the carotid bodies of SHR were significantly 1.3 times larger than those of NWR and WKY. In the carotid bodies of SHR, the percentage of relatively large vessels were similar to that in the carotid bodies of WKY, although the carotid bodies themselves were significantly larger than in WKY. In the carotid bodies of NWR and WKY, the density of NPY-immunoreactive varicose fibers were more numerous than that of VIP, SP, and CGRP fibers. These immunoreactive fibers were mainly associated with the vasculature and the clusters of glomus cells. The density of VIP varicose fibers in the carotid bodies of SHR were smaller than that in the carotid bodies of WKY, although that of SP, CGRP, and NPY fibers was similar to that in the carotid bodies of NWR and WKY. The present results suggest that the mechanisms of carotid body enlargement in hypertensive rats are different from those in hypoxic rats. [J Physiol Sci. 2006;56 Suppl:S136]
