NEUROPEPTIDE IMMUNOREACTIVITY IN LIGATURE-INDUCED NEUROMAS OF THE INFERIOR ALVEOLAR NERVE IN THE FERRET

Injury to branches of the trigeminal nerve can sometimes result in per sistent dysaesthesia. In an attempt to understand the aetiology of thi s condition we are currently investigating changes which occur at the injury site. In the present study we have examined the expression of s even neuropeptides, all of which have been implicated in nociceptive t ransmission, or have previously been shown to have altered expression following nerve injury. In 20 adult ferrets the inferior alveolar nerv e was sectioned and ligated, and recovery permitted for 3 days, 8 days , 3 weeks, 6 weeks or 12 weeks. Longitudinal sections of the neuromas were processed using immunohistochemical techniques to quantify the ex pression of substance P, calcitonin gene-related peptide, vasoactive i ntestinal polypeptide, galanin, somatostatin, enkephalin and neuropept ide Y. After 3 days, all of the neuropeptides were expressed at the in jury site. In the neuromas examined after longer recovery periods thes e levels of expression had declined and were similar to those found in the contralateral controls. This initial high level, followed by a de cline, parallels the incidence of ectopic neural activity recorded ele ctrophysiologically in the same model. It is, therefore, possible that the accumulation of neuropeptides at the injury site may play a role in the initiation or modulation of ectopic neural activity. (C) 1998 E lsevier Science B.V.