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 cha nges in oralis neuronal properties seen in cats 1-2 wk after the deafferent ation? could be blocked by local anaesthesia of the Vth nerve proximal to t he sites of pulp injury just before the actual deafferentation. The respons e 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 anaes thesia in one group of cats (group A) and without local anaesthesia in a se cond group (group B); a third group (group C) had no pulp removal but recei ved local anaesthesia. Consistent with the earlier data, there was a signif icantly increased incidence of neurones having an enlarged mechanoreceptive field, spontaneous activity and habituating tap sensitivity in group B com pared to group C, but no significant differences were found between the two deafferented groups (A and B). As local anaesthesia did not prevent the de velopment of pulp deafferentation-induced changes in the oralis neurones, i t is unlikely that an afferent barrage of impulses induced by the deafferen tation procedure was responsible for the neuroplastic changes that subseque ntly developed in the V subnucleus oralis. (C) 1999 Elsevier Science Ltd. A ll rights reserved.