Calcitonin gene-related peptide- and substance P-immunoreactive axons in the nucleus gracilis of the rat with special reference to axonal dystrophy: light and electron microscopic observations.
Calcitonin gene-related peptide (CGRP) and substance P (SP)-immunoreactive (IR) axons in the nucleus gracilis of normal rats (1-15 months of age) were studied by light and electron microscopy. Besides many CGRP-IR and SP-IR varicosities with normal appearance, we found a few swollen (nearly round or oval) varicosities with either CGRP or SP immunoreactivity. Swollen CGRP-IR varicosities were more frequently seen than SP-IR ones, appearing from 3 months of age and increasing in number and size (up to approximately 25 microns in diameter) with advancing age. At the electron microscopic (EM) level, CGRP-IR and SP-IR swollen varicosities showed dystrophic changes, i.e., many membranous dense bodies, and proliferation of microtubules and neurofilaments. CGRP-IR or SP-IR dystrophic axons also contained many mitochondria and sometimes made synaptic contacts with nonreactive dendrites (occasionally with non-IR axons). These findings suggest that the dystrophic CGRP and SP axonal profiles represent a functionally distinct subpopulation of axonal dystrophy in the nucleus gracilis and use CGRP or SP as a neuroactive substance. Using a double-immunostaining method, many of normal CGRP-IR axons were identified to be SP-IR. However, no single dystrophic varicosity was found to contain both CGRP and SP immunoreactivities. These findings suggest that CGRP and SP afferents are independently affected and progress to dystrophic changes.
1st Department of Anatomy, Osaka City University Medical School, Japan.
K
K
Fujiwara
S Y
SY
Baek
T
T
Arakawa
K
K
Kobayashi
H
H
Takagi
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure*; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D008297:Male; D008526:Medulla Oblongata / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000378:metabolism*
D013373:Substance P; D015740:Calcitonin Gene-Related Peptide