Effects of pre-emptive local anaesthesia on tooth pulp deafferentation-induced neuroplastic changes in cat trigeminal brainstem neurones

Previous work has shown increased excitability of brainstem neurones in the trigeminal (V) subnucleus oralis following the deafferentation produced by tooth-pulp removal. The present study was designed to determine if the changes in oralis neuronal properties seen in cats 1–2 wk after the deafferentation could be blocked by local anaesthesia of the Vth nerve proximal to the sites of pulp injury just before the actual deafferentation. The response properties of neurones recorded in V subnucleus oralis were determined in anaesthetized cats. One or two weeks before neuronal recording, the pulps of the posterior mandibular teeth were removed under local mandibular anaesthesia in one group of cats (group A) and without local anaesthesia in a second group (group B); a third group (group C) had no pulp removal but received local anaesthesia. Consistent with the earlier data, there was a significantly increased incidence of neurones having an enlarged mechanoreceptive field, spontaneous activity and habituating tap sensitivity in group B compared to group C, but no significant differences were found between the two deafferented groups (A and B). As local anaesthesia did not prevent the development of pulp deafferentation-induced changes in the oralis neurones, it is unlikely that an afferent barrage of impulses induced by the deafferentation procedure was responsible for the neuroplastic changes that subsequently developed in the V subnucleus oralis.