Abstract
Morphological changes and those in the peptidergic innervation were compared between the carotid bodies of the rats exposed to hypercapnic hypoxia (10% O2 and 6-7% CO2 for 8 weeks) and those exposed to normoxic hypercapnia (16% O2 and 6% CO2 for 8 weeks). In the sections stained with hematoxylin eosin,the carotid body was found to be enlarged several-fold in hypercapnic hypoxia, although the rate of vascular enlargement of carotid body was smaller in hypercapnic hypoxia than those in the isocapnic and hypocapnic hypoxia previously reported. In the chronically hypercapnic hypoxia, the density of parenchymal NPY fibers was significantly increased, that of VIP fibers was unchanged, and that of SP and CGRP fibers was decreased. In the normoxic hypercapnic carotid body, there were no morphological changes in comparison with the normoxic control carotid body. In addition, there were no distinvtive changes in the peptidergic innervation. These results suggest that the different levels of CO2 do not cause the morphological changes in the rat carotid body and the changes in the peptidergic innervation within the carotid body in normoxic conditions. Considered together with our recent findings, CO2 may have some additive effects on the chemoreceptor organs in hypoxic conditions. [Jpn J Physiol 55 Suppl:S106 (2005)]
