Calcitonin gene-related peptide (CGRP)-positive neurons and fibers in the cat periaqueductal grey matter.
The morphology and topographical distribution of neurons and terminals containing calcitonin gene-related peptide (CGRP) immunoreactivity in the cat periaqueductal grey (PAG) were studied using a rabbit antiserum raised against the C-terminal region of rat alpha-CGRP. In normal cats, numerous fibers, but rarely immunoreactive neurons, were observed in the PAG. CGRP-containing fibers showed bouton-like swellings along their length and expanded in terminal clusters of boutons. In many cases, CGRP-positive fibers were also observed in close association with small blood vessels. Immunoreactive fibers were particularly numerous at caudal PAG levels, mostly in its ventrolateral portion. In colchicine-treated cats, the pattern of CGRP-containing fibers was basically unchanged, despite a reduction of both the number of fibers and the intensity of fiber staining; in addition, numerous CGRP-positive neurons were found, mostly in the ventrolateral portion of the caudal PAG. These neurons were fusiform, spheroidal, and triangular in shape. The selective distribution of CGRP-positive elements in the PAG suggests a functional specialization of these neurons in the activation of pain-modulating mechanisms.
Conti
F
F
Instituto di Fisiologia umana, Università di Ancona, Italy.
Sternini
C
C
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002415:Cats; D003078:Colchicine / Q000494:pharmacology; D007150:Immunohistochemistry; D009411:Nerve Endings / Q000378:metabolism / Q000648:ultrastructure; D010487:Periaqueductal Gray / Q000166:cytology / Q000378:metabolism*
D015740:Calcitonin Gene-Related Peptide; D003078:Colchicine