The up-regulation of preprodynorphin mRNA in trigeminoparabrachial neuronsafter inflammation

Inflammation of the temporomandibular joint (TMI) produces an increase in p reprodynorphin (PPD) mRNA expression in the spinal trigeminal nucleus (Vsp) and paratrigeminal nucleus (Pa5) of the rat. In this study, we further dem onstrated that a portion of the TMJ inflammation-induced PPD mRNA positive neurons in the Vsp and Pa5 projected to the parabrachial nucleus (PB). In i nflamed rats, the percentage of trigemino- and paratrigeminoparabrachial ne urons with up-regulation of PPD mRNA was significantly increased in the ips ilateral Vsp (5.7 +/- 1.8%) and Pa5 (22.8 +/- 7.4%, n = 3) when compared wi th the contralateral side and with saline-treated controls (p < 0.05). Thes e results suggest that the selective up-regulation of PPD mRNA in the Vsp a nd Pa5 following TMJ inflammation involves ascending trigeminal nociceptive pathways. NeuroReport 11:845-847 (C) 2000 Lippincott Williams & Wilkins.