Calcitonin gene-related peptide and substance P immunoreactivity in rat trigeminal ganglia and brainstem following adjuvant-induced inflammation of the temporomandibular joint

The immunoreactivity of two inflammatory mediators, calcitonin gene-related peptide (CGRP) and substance P, was measured in the trigeminal ganglia and brainstem to characterize an adjuvant-induced inflammation within the rat temporomandibular joint at various acute (6, 24 and 48 h) and inter-mediate (10 day) time intervals. Concentrations of adjuvant-related neuropeptides were compared to those in both contralateral vehicle-related tissues and no n-injected controls. By 6 h, CGRP immunoreactivity in the trigeminal gangli a was significantly above that in contralateral vehicle-injected tissue. Th e CGRP had decreased at each of the following time-points. but remained sig nificantly elevated at 10 days. Substance P in the ganglion on the injected side was significantly increased for all four time periods. In brainstem s ubnucleus caudalis, CGRP was significantly increased for all four time peri ods. Substance P immunoreactivity in the subnucleus caudalis was significan tly increased for the initial three time periods, but by day 10 had been re duced to that of the control. These data show that the pattern of changes i n neuropeptides following the induction of inflammation is different betwee n substance P and CGRP. Moreover, the pattern of change varies between the brainstem and the trigeminal ganglion. This suggests that the two neuropept ides may have different roles in the inflammatory process, and that this pr ocess may be modulated by different mechanisms at the brainstem and ganglio n. (C) 2000 Elsevier Science Ltd. All rights reserved.