Fig. 5

Recovery kinetics of TTX-R Na⁺ channels in dural afferent neurons. A. a, Typical second (P₂) traces of TTX-R I_Na elicited by a two-pulse protocol in small- (left) and medium-sized (right) DiI-positive neurons. TTX-R I_Na were induced by the conditioning pulse (P₁: -10 mV; 500 ms duration), which was followed by the second test pulse (P₂: -10 mV; 50 ms duration). The second TTX-R I_Na was recovered with various interpulse intervals of 1–5,000 ms at a potential of -80 mV (see Supplementary Fig. S3A). b, Kinetics of the recovery from inactivation of TTX-R Na⁺ channels in small- (open circles) and medium-sized (closed circles) DiI-positive neurons. The P₂/P₁ ratio of TTX-R I_Na was plotted against the recovery duration. The points and error bars represent the mean and SEM from 18 small- and 33 medium-sized DiI-positive neurons. The continuous lines represent the best fits using a triple exponential function. B. a, Scatter plot of the fast time constant (τ_fast) against membrane capacitance (Cm) (n = 51). The linear trend line represents the best fit using a least-squares fit (r = 0.73). b, The mean τ_fast values in small- (S) and medium-sized (M) DiI-positive neurons. The columns and error bars represent the mean and SEM from 18 small- and 33 medium-sized DiI-positive neurons. **; p < 0.01 (unpaired t-test). C. Scatter plot of the fast time constant (τ_fast) against the density of TTX-R I_NaP (n = 51). The linear trend line represents the best fit using a least-squares fit (r = 0.75). D. Schematic illustration of the two-pulse protocol. TTX-R I_Na were induced by the conditioning prepulse (P₁: -10 mV; 50 ms, 100 ms, 200 ms, and 500 ms durations), which was followed by the second test pulse (P₂: -10 mV; 50 ms duration). The second TTX-R I_Na was recovered with various interpulse intervals of 1–5,000 ms at a potential of -80 mV. E. Kinetics of the recovery from inactivation of TTX-R Na⁺ channels with conditioning prepulse durations of 50 ms (open circles), 100 ms (closed circles), 200 ms (closed diamonds), and 500 ms (closed diamonds) in small- (a) and medium-sized (b) DiI-positive neurons. The P₂/P₁ ratio of TTX-R I_Na was plotted against the recovery duration. The points and error bars represent the mean and SEM from seven small- and eight medium-sized DiI-positive neurons. The continuous lines represent the best fits using a triple exponential function. F. The mean values of τ_fast (a) and A_fast (b) at different conditioning prepulse durations. The points and error bars represent the mean and SEM from seven small- and eight medium-sized DiI-positive neurons. Notably, the τ_fast values obtained from small-sized DiI-positive neurons were greatly reduced as the conditioning prepulse duration was shortened. *; p < 0.05, **; p < 0.01, n.s; not significant (unpaired t-test)