The effect of unilateral sympathectomy and cavity preparation on peptidergic nerves and cells in rat dental pulp

Recent evidence suggests interactions between primary afferent nociceptors and postganglionic sympathetic efferents in the pathogenesis of inflammatio n. The effect of unilateral removal of the superior cervical ganglion on th e innervation pattern of nerve fibers immunoreactive (IR) to calcitonin gen e-related peptide (CG;RP), substance P (SP), and neuropeptide Y (NPY), as w ell as the occurrence of cells in the injured and uninjured rat molar pulp, was investigated. Light microscopic immunocytochemistry demonstrated that the molar pulps contralateral to the sympathectomy contained a NPY-IR nerve fiber network more dense and heavily stained than unoperated control rats. The NPY-IR fibers showed, however, no sprouting after deep cavity preparat ion. There was no compensatory increase in CGRP- and SP-IR nerve fibers in the dental pulp after unilateral sympathectomy, although a significant incr ease in cells IR to CORP and SP was found in the ipsilateral trigeminal gan glion. Unilateral sympathectomy induced a significant increase in cell dens ity both in the inflamed and in the uninflamed dental pulp bilaterally. Our results demonstrate, for the first time, a trophic effect of the sympathet ic nerves on cells in the dental pulp, indicating that an imbalance of symp athetic nerves may induce inflammation and pain in teeth. (C) 2001 Academic Press.