Figure 2. Effect of eugenol on I_Ba in capsaicin-sensitive and capsaicin-insensitive neurons. (A) Time course of the effect of capsaicin (1 µM) and eugenol (1 mM) on I_Ba. The I_Ba inhibition by eugenol (1 mM) was observed in capsaicin-sensitive dental primary afferent neurons (n = 20). (B) In dental primary afferent neurons in which I_Ba was not inhibited by capsaicin (1 mM), eugenol (1 mM) also inhibited I_Ba, indicating that the inhibitory effects of eugenol on I_Ba can be induced without the involvement of TRPV1 activation. (C) Dose-response relationship of eugenol-induced I_Ba inhibition in capsaicin-sensitive dental primary afferent neurons (mean ± SEM). The numbers in parentheses represent the numbers of cells studied. (D) The summary of I_Ba inhibition in dental primary afferent neurons. 1 mM eugenol (Eug)-induced I_Ba inhibition in capsaicin-insensitive neurons (Cap-Ins) was similar to that obtained in capsaicin-sensitive neurons (Cap-S). Capsazepine (CZP, 10 µM) failed to block eugenol (1 mM)-induced I_Ba inhibition completely. The I_Ba inhibition by the combined application of eugenol and CZP was not significantly different from that of eugenol (mean ± SEM, p > 0.05).