Pulpal exposure alters neuropeptide levels in inflamed dental pulp and trigeminal ganglia: Evaluation of axonal transport

Dental pulp is richly innervated with neurons containing calcitonin gene-re lated peptide (CGRP) or substance P (SP), Prior studies have demonstrated t hat inflammation alters these pulpal neuropeptides, In this study, we used a radioimmunoassay to evaluate the specificity of this response and the con tribution of axonal transport. Rat mandibular molars were exposed and immun oreactive CGRP (iCGRP) and immunoreactive SP were measured. At 7 to 14 days after exposure, both pulpal iCGRP (73%) and immunoreactive SP (135%) displ ayed peak increases above control levels. This response was somatotopically restricted, with no changes observed in contralateral (intact) molars, or in ipsilateral mandibular molars after exposure of maxillary molars. Transe ction of the inferior alveolar nerve on day 13 significantly reduced pulpal levels of iCGRP on day 14, Collectively, these studies indicate that pulpa l inflammation evokes a selective alteration in neuropeptide levels, due at least in part to alterations in transport or synthesis of neuropeptides in the trigeminal ganglion.