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SCOPUS 학술저널

Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons

Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons

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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 &#1345;,&#1346;-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 &#1345;,&#1346;-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.

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