The distribution patterns of nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP), substance P(SP) and neuropeptide Y(NPY) were studied and compared with innervation visualized by antibody to neurofilament protein-200(NFP) in developing dental structure in rats aged 13 to 27 days.
A substantially greater part of the nerve fibers was immunoreactive to NFP and CGRP than to SP and NPY in all stage of dental development. In the bell stage, nerve fibers immunoreactive to NFP and CGRP were found in the dental follicle but not in the dental papilla and stellate reticulum. In the advanced bell stage, after initiation of dentine and enamel formation, regular NFP and CGRP-immunoreactive fibers were found in the periphery and beneath of dental papilla in the dental follicle. In the stage that crown formation was completed and the root formation began, SP and NPY-immunoreactive fibers were first observed mainly in connection with larger blood vessles in the basal part of pulp. Concomitantly with the begining of root formation, a subodontoblastic nerve plexus immunoreactive to NFP and CGRP was formed and NFP and CGRP-immunoreactive fibers were found within the odontoblastic layer. At the stage of root development and eruption, NFP and CGRP-immunoreactive fibers were rich in the subodonoblastic nerve plexus, odontoblastic layer and apical third of periodontal ligament. While SP and NPY-immunoreactive fibers occured occasionally around the blood vessels in the pulp. When the teeth occluded fully, much more NFP and CGRP-immunoreactive fibers occured at the odontoblastic layer and subodontoblastic nerve plexus in the pulp horns and coronal pulp and apical third of periodontal ligament. No apparent difference in the occurrence and distribution of SP and NPY-immunoreactive fibers was found in comparison with those of preceding developmental stage.
Hence, it may be concluded that the developing innervation of NFP and CGRP-immunoreactive fibers is well correlated with the stage of development of individual teeth.
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