Effects of Eugenol on T-type Ca2+ Channel Isoforms

• Published in: The Journal of pharmacology and experimental therapeutics 2013-11, Vol.347 (2), p.310-317
• Main Authors: Seo, Haengsoo, Li, Hai Ying, Perez-Reyes, Edward, Lee, Jung-Ha
• Format: Article
• Language: English
• Subjects: Analgesics - pharmacology; Calcium Channel Blockers - pharmacology; Calcium Channels, T-Type - genetics; Calcium Channels, T-Type - metabolism; current-voltage; Eugenol - pharmacology; HEK; HEK293 Cells; high-voltage activated; human embryonic kidney; Humans; HVA; I-V; Kinetics; low-voltage activated; LVA; Membrane Potentials - drug effects; Neurons, Afferent - cytology; Neurons, Afferent - drug effects; Neurons, Afferent - metabolism; Patch-Clamp Techniques; Protein Binding; Protein Isoforms; Transfection; trigeminal ganglion; Trigeminal Ganglion - cytology; Trigeminal Ganglion - drug effects; Trigeminal Ganglion - metabolism
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.113.207936

Eugenol has been used as an analgesic in dentistry. Previous studies have demonstrated that voltage-gated Na+ channels and high-voltage-activated Ca2+ channels expressed in trigeminal ganglion (TG) neurons sensing dental pain are molecular targets of eugenol for its analgesic effects. However, it has not been investigated whether eugenol can affect T-type Ca2+ channels, which are known to be detected in the afferent neurons. In this report, we investigate how eugenol can influence cloned T-type channel isoforms expressed in HEK293 cells, using whole-cell patch clamp. Application of eugenol inhibited Cav3.1, Cav3.2, and Cav3.3 currents in a concentration-dependent manner with IC50 values of 463, 486, and 708 μM, respectively. Eugenol was found to negatively shift the steady-state inactivation curves of the T-type channel isoforms, but it did not shift their activation curves. In addition, eugenol had little effect on the current kinetics of Cav3.1 and Cav3.2, but it accelerated the inactivation kinetics of Cav3.3 currents. Reduction of channel availability enhanced eugenol inhibition sensitivity for Cav3.1 and Cav3.2, but not for Cav3.3. Moreover, eugenol inhibition of T-type channel isoforms was found to be use dependent. Finally, we show that the T-type currents recorded from rat TG neurons were inhibited by eugenol with a similar potency to Cav3.1 and Cav3.2 isoforms. Taken together, our findings suggest that T-type Ca2+ channels are additional molecular targets for the pain-relieving effects of eugenol.