Reduction in sympathetic neuronotrophic activity in the pulp of the cat canine tooth after denervation

Abstract

Most of the nerve fibres supplying the mandibular canine on one side were interrupted by sectioning the inferior alveolar nerve (IAN) and, after 1 week, the trophic activity in each mandibular canine pulp was assessed in an in vitro assay using sympathetic neurones from 11-day chick embryos as test cells. In eight of nine animals tested, neuronotrophic activity in the denervated pulp was markedly lower than in the contralateral control pulp. Antiserum to mouse nerve growth factor had no effect on the trophic activity in either control or denervated pulps. Thus, the pulp differs from other peripheral tissues, which undergo increases in neuronotrophic activity after denervation. The basis of this difference may be the high innervation density of the pulp. The IAN distal to the site of nerve transection also had reduced survival-promoting activity.