CGRP1 and NK1 receptors in postnatal, developing rat dental tissues.

There is little evidence that neuropeptides such as substance P (SP) and calcitonin gene-related peptide (CGRP) participate in the regulation of tooth development. The aim of this study was to analyse the expression of their respective receptors, neurokinin (NK) 1 and CGRP1 receptor, in postnatal developing rat molars and supporting tissues, thereby localizing the target areas for neuropeptide activity. Mol:WIST rats were killed at 7, 14 and 21 d after birth and upper and lower jaws were processed for immunohistochemistry. At early crown stage (P7), only a few individual cells in the dental follicle were receptor positive. At the onset of root formation (P14), post-secretory ameloblasts, cells in the stratum intermedium, the reduced enamel epithelium and the developing alveolar bone demonstrated both NK1 and CGRP1 receptor immunoreactivity. The CGRP1 receptor sites were occasionally evident on cells in the odontoblast layer. At advanced root development (P21), neuropeptide receptor expression was evident on cells close to the developing dentin, cementum and alveolar bone. These data demonstrate dynamic changes in the localization of NK1 and CGRP1 receptors in developing rat dental tissues and indicate an active role for their ligands in the regulation of crown and root development.