Studies of the localization and distribution of the trigeminal nerve fibres and SP- and CGRP-containing nerve fibres in rat gingivae with experimental gingivitis or without gingivit

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The sensory innervation of junctional and oral sulcular epithelium was investigated by use of anterograde transport of wheat-germ agglutinin-horseradish peroxidase from the trigeminal ganglion in rats. By light microscopy, labeled intraepithelial nerve fibers were observed forming a dense plexus in the apical two-thirds of the junctional epithelium. In contrast to the junctional epithelium, the oral sulcular epithelium was sparsely innervated. By electron microscopy, labeled intraiepithelial axon terminals or varicosities were demonstrated to be in close contact both with junctional epithelial cells and neutrophils. These varicosities frequently contained large granular and small clear vesicles.The beginning of nerve fibers with Substance P(SP)- or calcitonin gene-related peptide like immunoreactivity(CGRP-IR)in the developing junctional epithelium was examined by the avidin-biotincomplex-method. - In 21-day old rats, varicose fibers were first entered the coronal and middle portions of reduced enamel epithelium. In 23-day-old rats, many fibers with SP- or CGRP-IR were seen in the basal layers, but only a few in the superficial layers of the junctional epithelium. In 28 to 32-day-old rats, numerous fibers with SP- or CGRP-IR were distributed in the whole junctional epithelium.Nerve fibers with SP- or CGRP-IR in the labial gingival tissues of mandibular incisors affected with gingivitis and without gingivitis were observed. In the gingivitis affected rats, the fibers showed a marked increase in number and density compared with the normal rats ; many of them were located close to blood vessels. At the enamel side of the periosteum, many nerve fibers with SP- or CGRP-IR were located around the vessels and some fibers were close to the alveolar bone, but few were found along the oral epithelial side of the periosteum.