Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons
Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제12권 제6호
- : SCOPUS, SCIE, KCI등재
- 2008.01
- 315 - 322 (8 pages)
Eugenol is widely used in dentistry to relieve pain. We have recently demonstrated voltage-gated Na<sup>+</sup> and Ca<sup>2+</sup> channels as molecular targets for its analgesic effects, and hypothesized that eugenol acts on P2X<sub>3</sub>, another pain receptor expressed in trigeminal ganglion (TG), and tested the effects of eugenol by whole-cell patch clamp and Ca<sup>2+</sup> imaging techniques. In the present study, we investigated whether eugenol would modulate 5 -triphosphate (ATP)-induced currents in rat TG neurons and P2X<sub>3</sub>-expressing human embryonic kidney (HEK) 293 cells. ATP-induced currents in TG neurons exhibited electrophysiological properties similar to those in HEK293 cells, and both ATP- and Ձ,Ղ-meATP-induced currents in TG neurons were effectively blocked by TNP-ATP, suggesting that P2X<sub>3</sub> mediates the majority of ATP-induced currents in TG neurons. Eugenol inhibited ATP-induced currents in both capsaicin-sensitive and capsaicin-insensitive TG neurons with similar extent, and most ATP-responsive neurons were IB4-positive. Eugenol inhibited not only Ca<sup>2+</sup> transients evoked by Ձ,Ղ-meATP, the selective P2X<sub>3</sub> agonist, in capsaicin-insensitive TG neurons, but also ATP-induced currents in P2X<sub>3</sub>-expressing HEK293 cells without co-expression of transient receptor potential vanilloid 1 (TRPV1). We suggest, therefore, that eugenol inhibits P2X<sub>3</sub> currents in a TRPV1-independent manner, which contributes to its analgesic effect.