Tooth injury increases expression of the cold sensitive TRP channel TRPA1 in trigeminal neurons

Transient receptor potential (TRP) channels, a family of structurally related proteins have been implicated in the sensation of pain and hyperalgesia caused by exogenous and endogenous agonists, as well as touch, pH, and temperature. The objective of this study was to determine the effects of tooth injury on the expression of the cold sensitive channel TRPA1, in the trigeminal ganglion, the primary source of sensory and nociceptive innervation of teeth. We analyzed TRPA1 expression in a rodent model of tooth injury, by Western blot analyses of proteins extracted from trigeminal ganglia. We found that TRPA1 was selectively increased in trigeminal ganglia innervating injured teeth when compared to TRPA1 expression in trigeminal ganglia innervating healthy teeth. Our results provide the first evidence of increased expression of a cold-sensitive TRP channel in trigeminal ganglia after pulp exposure, and are consistent with the possibility that increased expression and function of TRPA1 in trigeminal neurons contributes to hyperalgesia and allodynia following tooth injury.