Fig. 7

Inflammatory mediator-induced changes in the properties of TTX-R Na⁺ channels in small-sized dural afferent neurons. A. a, Typical traces of TTX-R I_Na recorded from IM-treated (gray) and vehicle-treated (black) small- (left) and medium-sized (right) DiI-positive neurons. TTX-R I_Na were elicited by voltage step pulses (100 ms duration; -10 mV depolarization at a V_H of -80 mV). Notably, TTX-R I_NaP were larger in the IM-treated group than those in the vehicle-treated group in small-sized DiI-positive neurons but not in medium-sized DiI-positive neurons. b, Scatter plot of the density of TTX-R I_NaP obtained from IM-treated DiI-positive neurons (gray circles; n = 30) and vehicle-treated DiI-positive neurons (open circles; n = 42) against membrane capacitance (Cm). The linear trend lines represent the best fits using a least-squares fit (IM-treated group: r = 0.50; vehicle-treated group: r = 0.69). B. The mean values of the current density of TTX-R I_NaP recorded from IM-treated and vehicle-treated small- (a) and medium-sized (b) DiI-positive neurons. The columns and error bars represent the mean and SEM from 32 (17 for vehicle-treated and 15 for IM-treated) and 40 (25 for vehicle-treated and 15 for IM-treated) neurons for small- and medium-sized DiI-positive neurons, respectively. **; p < 0.01, n.s; not significant (unpaired t-test). C. a, Typical traces of TTX-R I_Ramp recorded in small- (left) and medium-sized (right) DiI-positive neurons. TTX-R I_Ramp were elicited by voltage-ramp stimuli every 15 s (6 s duration; up to + 10 mV depolarization at a V_H of -80 mV; 15 mV/s). Notably, TTX-R I_Ramp was larger in the IM-treated group than in the vehicle-treated group in small- but not medium-sized DiI-positive neurons. b, Scatter plot of the density of TTX-R I_Ramp obtained from IM-treated DiI-positive neurons (gray circles; n = 30) and vehicle-treated DiI-positive neurons (open circles; n = 42) against membrane capacitance (Cm). The linear trend lines represent the best fits using a least-squares fit (IM-treated group: r = 0.55; vehicle-treated group: r = 0.59). D. The mean values of the current density of TTX-R I_Ramp recorded from IM- and vehicle-treated small- (a) and medium-sized (b) DiI-positive neurons. The columns and error bars represent the mean and SEM from 32 (17 for vehicle-treated and 15 for IM-treated) and 40 (25 for vehicle-treated and 15 for IM-treated) neurons for small- and medium-sized DiI-positive neurons, respectively. **; p < 0.01, n.s; not significant (unpaired t-test). E. a, Voltage-fast inactivation relationships of TTX-R Na⁺ channels in vehicle-treated (open circles) and IM-treated (closed circles) small-sized DiI-positive neurons. The points and error bars represent the mean and SEM from 16 vehicle-treated and 17 IM-treated small-sized DiI-positive neurons. The continuous lines represent the best fits using a Boltzmann function. b, The mean values of V_{50, inactivation} in vehicle- and IM-treated small-sized DiI-positive neurons. The columns and error bars represent the mean and SEM from 16 vehicle-treated and 17 IM-treated small-sized DiI-positive neurons. *; p < 0.05 (unpaired t-test). F. a, Voltage-slow inactivation relationships of TTX-R Na⁺ channels in vehicle-treated (open circles) and IM-treated (closed circles) small-sized DiI-positive neurons. The points and error bars represent the mean and SEM from 15 vehicle-treated and 17 IM-treated small-sized DiI-positive neurons. The continuous lines represent the best fits using a Boltzmann function. b, The mean values of the V_{50, inactivation} in vehicle- and IM-treated small-sized DiI-positive neurons. The columns and error bars represent the mean and SEM from 15 vehicle-treated and 17 IM-treated small-sized DiI-positive neurons. *; p < 0.05 (unpaired t-test). G. a, Time course of the amplitude of TTX-R I_Na during a train of 20 pulses in vehicle-treated (open circles) and IM-treated (closed circles) small-sized DiI-positive neurons. The peak amplitudes of TTX-R I_Na were normalized to the respective first amplitude and plotted against the pulse number. The points and error bars represent the mean and SEM from 15 vehicle-treated and 13 IM-treated small-sized DiI-positive neurons. b, The mean values of the P₂₀/P₁ ratio for vehicle- and IM-treated small-sized DiI-positive neurons. The columns and error bars represent the mean and SEM from 15 vehicle-treated and 13 IM-treated small-sized DiI-positive neurons. **; p < 0.01 (unpaired t-test). H. Kinetics for the development of inactivation of TTX-R Na⁺ channels in vehicle-treated (open circles) and IM-treated (closed circles) small-sized DiI-positive neurons. The P₂/P₁ ratio of TTX-R I_Na was plotted against the duration of the conditioning prepulse. The points and error bars represent the mean and SEM from 16 vehicle-treated and 19 IM-treated small-sized DiI-positive neurons. The continuous lines represent the best fits using a double exponential function. I. Mean values of τ_fast (a) and τ_slow (b) in vehicle- and IM-treated small-sized DiI-positive neurons. The columns and error bars represent the mean and SEM from 16 vehicle-treated and 19 IM-treated small-sized DiI-positive neurons. **; p < 0.01 (unpaired t-test). J. Kinetics of the recovery from inactivation of TTX-R Na⁺ channels in vehicle-treated (open circles) and IM-treated (closed circles) small-sized 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 15 vehicle-treated and 18 IM-treated small-sized DiI-positive neurons. The continuous lines represent the best fits using a triple exponential function. K. The mean τ_fast (a), τ_intermediate (b), and τ_slow (c) values in vehicle- and IM-treated small-sized DiI-positive neurons. The columns and error bars represent the mean and SEM from 15 vehicle-treated and 18 IM-treated small-sized DiI-positive neurons. **; p < 0.01, n.s; not significant (unpaired t-test)