Eugenol inhibits K+ currents in trigeminal ganglion neurons.
Eugenol, a natural capsaicin congener, is widely used in dentistry. Eugenol inhibits voltage-activated Na(+) and Ca(2+) channels in a transient receptor potential vanilloid 1 (TRPV1)-independent manner. We hypothesized that eugenol also inhibits voltage-gated K(+) currents, and investigated this in rat trigeminal ganglion neurons and in a heterologous system using whole-cell patch clamping. Eugenol inhibited voltage-gated K(+) currents, and the inhibitory effects of eugenol were observed in both capsaicin-sensitive and capsaicin-insensitive neurons. Pre-treatment with capsazepine, a well-known antagonist of TRPV1, failed to block the inhibitory effects of eugenol on K(+) currents, suggesting no involvement of TRPV1. Eugenol inhibited human Kv1.5 currents stably expressed in Ltk(-) cells, where TRPV1 is not endogenously expressed. We conclude that eugenol inhibits voltage-gated K(+) currents in a TRPV1-independent manner. The inhibition of voltage-gated K(+) currents is likely to contribute to the irritable action of eugenol.


BACKGROUND
human Kv1.5 channel, hKv1.5; transient receptor potential vanilloid 1, TRPV1.
Li
H Y
HY
Department of Physiology and Program in Molecular and Cellular Neuroscience, School of Dentistry and Dental Research Institute, Seoul National University, 28-2 Yeongeon-Dong Chongno-Ku, Seoul, Korea.
Park
C-K
CK
Jung
S J
SJ
Choi
S-Y
SY
Lee
S J
SJ
Park
K
K
Kim
J S
JS
Oh
S B
SB
D000704:Analysis of Variance; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D005054:Eugenol / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D009475:Neurons, Afferent / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D024642:Potassium Channels, Voltage-Gated / Q000037:antagonists & inhibitors*; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000502:physiology; D012668:Trigeminal Ganglion / Q000166:cytology / Q000187:drug effects*
D024642:Potassium Channels, Voltage-Gated; D050916:TRPV Cation Channels; D005054:Eugenol; D002211:Capsaicin