Peripheral nerves and mast cells in normal buccal mucosa

The topographical distribution and relation to mast cells of PGP 9.5 (protein gene product 9.5. a major cytoplasmic neuron‐specific protein with ubiquitin C‐terminal hydrolase activity) and neurofilament (intermediate neuron‐specific cytoskeletal filaments) in normal human buccal mucosa was studied in five healthy volunteers. Morphometric analysis disclosed the densest innervation to be in the middle layers of the lamina propria, with a mean number of 5.9–6.1 PGP 9.5 and/or neurofilament‐immunoreactive nerve fiber profiles per one mm2. In contrast, the mean mast cell number decreased from 110/mm2 to 46/mm2 from superficial to deep lamina propria, being 69–72/mm2 in the most densely innervated middle layers. Only 16–17% of all fiber profiles contained substance P and 51–54% calcitonin gene‐related peptide (CGRP). Finally, analysis of the spatial relationship between nerve fiber profiles and mast cells in a double staining procedure disclosed no preferential neuron‐effector associations. All these findings suggest that such a relationship does not exist between peripheral nerves and mast cells in normal buccal mucosa.