Figure 3. Effect of eugenol on two types of I_Na in dental primary afferent neurons. Both TTX-sensitive (TTX-s) and TTX-resistant (TTX-r) I_Na were present in dental primary afferent neurons. (Aa) TTX-r I_Na was predominant in small neurons (< 25 µm). TTX-s I_Na is the difference current of total I_Na and TTX-r I_Na. (Ab) TTX-r I_Na was blocked by 1 mM eugenol (n = 7). (B) TTX-s I_Na, which was predominant in large neurons (> 35 µm), was also blocked by 1 mM eugenol (n = 5). A and B are representative traces illustrating the effect of eugenol from TTX-r and TTX-s neurons, respectively. (C) The summary of TTX-r I_Na and TTX-s I_Na inhibition in dental primary afferent neurons. The extent of inhibition by eugenol on TTX-r I_Na was similar to that on TTX-s I_Na (mean ± SEM, p > 0.01). The numbers in parentheses represent the number of cells studied.