Peptidergic innervation in the rat carotid body after 2, 4, and 8 weeks of hypocapnic hypoxic exposure.
The distribution and abundance of neuropeptide-containing nerve fibers were examined in the carotid bodies of rats exposed to hypocapnic hypoxia (10% O2 in N2) for 2, 4, and 8 weeks. The carotid bodies after 2, 4, and 8 weeks of hypoxic exposure were enlarged by 1.2-1.5 times in the short axis, and 1.3-1.7 times in the long axis in comparison with the normoxic control ones. The enlarged carotid bodies contained a number of expanded blood vessels. Mean density per unit area (10(4) microm2) of substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactive fibers was transiently high in the carotid bodies after 4 weeks of hypoxic exposure, and decreased significantly to nearly or under 50% after 8 weeks of hypoxic exposure. Density of vasoactive intestinal polypeptide (VIP) immunoreactive fibers increased significantly in all periods of hypoxic exposure observed, and was especially high in the carotid bodies after 4 weeks of hypoxic exposure. Density of neuropeptide Y immunoreactive fibers was unchanged in the carotid bodies during hypoxic exposure. These characteristic changes in the density of SP, CGRP, and VIP fibers in the carotid bodies after 4 weeks of hypoxic exposure suggest that the role of these neuropeptide-containing fibers may be different in the carotid bodies after each of three periods of hypoxic exposure, and that the peptidergic innervation after 8 weeks of hypoxic exposure may show an acclimatizing state.
Kusakabe
T
T
Laboratory for Anatomy and Physiology, Department of Sport and Medical Science, Kokushikan University, Tokyo, Japan. kusakabe@kokushikan.ac.jp
Hirakawa
H
H
Matsuda
H
H
Kawakami
T
T
Takenaka
T
T
Hayashida
Y
Y
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis; D002344:Carotid Body / Q000378:metabolism / Q000502:physiology*; D004396:Coloring Agents; D004801:Eosine Yellowish-(YS); D005456:Fluorescent Dyes; D006416:Hematoxylin; D016857:Hypocapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D007150:Immunohistochemistry; D009131:Muscle, Smooth, Vascular / Q000294:innervation / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009478:Neuropeptide Y / Q000096:biosynthesis; D009479:Neuropeptides / Q000096:biosynthesis / Q000502:physiology*; D051381:Rats; D013373:Substance P / Q000096:biosynthesis; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D004396:Coloring Agents; D005456:Fluorescent Dyes; D009478:Neuropeptide Y; D009479:Neuropeptides; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D015740:Calcitonin Gene-Related Peptide; D004801:Eosine Yellowish-(YS); D006416:Hematoxylin