Immunohistochemical and Electron Microscopic Study on the Somatosensory Receptive System in Orofacial Region

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The findings obtained from this study are summarized as follows.1. A major population of pulpal nerves in human teeth showed an intense nerve growth factor receptor (NGFR)-immunoreactivity. Immunoelectron microscopy demonstrated that the NGFR-immunoreactivity was localized on the axoplasmic membrane in both unmyelinated and naked axons, but not in myelinated fibers. A positive immunoreaction was also found in Schwann cells in unmyelinated fibers. Fibroblasts, cellular elements other than axons and some of Schwann cells were immunonegative.2. Despite variation in development among species, Ruffini endings are accepted as essential mechanoreceptors, sensitive to tension of collagen fibers, in the periodontal ligament. Ruffini endings in the periodontal ligament were associated with terminal Schwann cells whose cytoplasm contained wellーdeveloped rough endoplasmic reticulum and Golgi apparatus. In addition to ordinary functions of supporting and nourishing of axon terminals, these cells we … More re able to synthesize cholinesterase and proteoglycans.3. The response of pulpal nerves to dentin injury was investigated in rat molars by immunostaining for neurofilament protein. The distribution and shape of pulpal nerves reacted dynamically in response to cavity preparations, indicating possible involvement of the pulpal nerves in the tissue repair process following cavity preparations.4. The response of the periodontal nerve fibers to orthodontic tooth movement was investigated in rat molars by use of immunohistochemistry for calcitonin geneーrelated peptide (CGRP). The dynamic changes of CGRP-immunoreactive nerves in the periodontal ligament was recognized during the tooth movement. It is suggested that the periodontal nerves are involved in inducing pain sensation in patients.5. Although the presence of a variety of mechanoreceptors in the temporomandibular joint has been suggested by electrophysiological studies, no specialized nerve terminals except free nerve endings were observed in this immunohistochemical study. Less