Basic researches on the high altitude training : mechanism of vascular and pulmonary systems

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Morphological changes in the carotid bodies of three types of denervated rats were examined after hypocapnic hypoxic exposure (10% 02 in N2 for 8 weeks). The carotid bodies of rats denervated of both sinus and sympathetic nerves (SD+S) were significantly enlarged with vascular expansion. But there were no significant changes in the carotid bodies of rats denervated of the sinus nerve alone (SD) or rats denervated of the sinus, sympathetic, and vagal nerves (SD+S+V). These findings indicate that there would be no morphological changes in the carotid bodies of rats denervated of the sympathetic and vagal nerves rats or rats with these two nerves intact (SD rats). This suggests that the enlargement of the carotid body in hypoxic conditions may depend on well-balanced sympathetic and para-sympathetic control.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 carotid bodies of SHR were greater than those of NWR and WKY. 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. These findings suggest that the mechanisms of carotid body enlargement in hypertensive rats are different from those in hypoxic rats.