ANATOMIC RELATIONSHIP BETWEEN SUBSTANCE-P-IMMUNOREACTIVE AND CGRP-IMMUNOREACTIVE NERVE-FIBERS AND MAST-CELLS IN THE PALATAL MUCOSA OF THE RAT

The study describes the distribution of mast cells and of substance P (SP) and calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers in the rat palatal mucosa, focusing on the anatomic relationship between these tissue elements. The maxilla of 10-14-wk-old rats was dissected free, fixed, demineralized and frozen. Consecutive sections were stained with avidin peroxidase or processed for immunohistochemistry. In order to define the correlation between nerve fibers and mast cells, double staining techniques were used. The distance between each avidin-positive mast cell and the nearest detectable nerve fiber was determined. 5-Hydroxytryptamine-(5-HT) and avidin peroxidase-positive mast cells were frequently seen in the palatal mucosa but were rarely found in the gingival area. A large number of nerve fibers showing SP- and CGRP-like immunoreactivity were seen, particularly in association with blood vessels. Some nerve fibers were located in contact with or very close to the mast cells but the vast majority of mast cells showed no close anatomic association to nerve fibers. The nerve fibers and mast cells were mainly concentrated to the same regions in the palatal mucosa where blood vessels occurred. The observations suggest that in the rat palatal mucosa the main functional relationship relates to SP/CGRP and the blood vessels, and only to a minor degree to SP/CGRP and mast cells.