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Fig. 4 | The Journal of Headache and Pain

Fig. 4

From: Contribution of tetrodotoxin-resistant persistent Na+ currents to the excitability of C-type dural afferent neurons in rats

Fig. 4

Inactivation kinetics of TTX-R Na+ channels in dural afferent neurons. A. a, Typical second (P2) traces of TTX-R INa elicited by a two-pulse protocol in small- (left) and medium-sized (right) DiI-positive neurons. TTX-R INa were induced by the first conditioning pulse (P1: -10 mV; 2–8,000 ms duration), which was followed by the second test pulse (P2: -10 mV; 50 ms duration) with an interpulse interval of 20 ms at a potential of -80 mV (Supplementary Fig. S2A). b, Kinetics for the development of 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 INa was plotted against the duration of the conditioning prepulse. The points and error bars represent the mean and SEM from 28 small- and 47 medium-sized DiI-positive neurons. The continuous lines represent the best fits using a double exponential function. B. a, Scatter plot of the weighted time constant (τfast) against membrane capacitance (Cm) (n = 75). The linear trend line represents the best fit using a least-squares fit (r = 0.57). b, The mean values of τfast in small- (S) and medium-sized (M) DiI-positive neurons. The columns and error bars represent the mean and SEM from 28 small- and 47 medium-sized DiI-positive neurons, respectively. **; p < 0.01 (unpaired t-test). C, Scatter plot of τfast against the density of TTX-R INaP (n = 75). The linear trend line represents the best fit using a least-squares fit (r = 0.69). D, Schematic illustration of the two-pulse protocol. TTX-R INa were induced by the first conditioning pulses (P1: -10 mV; 2–8,000 ms duration), which were followed by the second test pulses (P2: -10 mV; 50 ms duration). The second TTX-R INa was recovered with interpulse intervals of 5, 10, 20, 50, and 100 ms at a potential of -80 mV. E. Kinetics for the development of inactivation of TTX-R Na+ channels with recovery durations of 5 ms (open circles), 20 ms (closed circles), and 100 ms (open diamonds) in small- (a) and medium-sized (b) DiI-positive neurons. The P2/P1 ratio of TTX-R INa was plotted against the duration of the conditioning prepulse. The points and error bars represent the mean and SEM from eight small- and eight medium-sized DiI-positive neurons. The continuous lines represent the best fits using a double exponential function. F. The mean values of τfast (a) and Afast (b) at different recovery durations of a two-pulse protocol in small- (open circles) and medium-sized (closed circles) DiI-positive neurons. The points and error bars represent the mean and SEM from eight small- and eight medium-sized DiI-positive neurons. Notably, τfast values were not related to the recovery duration in both types of DiI-positive neurons. **; p < 0.01, n.s; not significant (unpaired t-test). G. Schematic illustration of the two-pulse protocol. TTX-R INa were induced by the first conditioning pulse (P1: 2–8,000 ms duration), which was followed by the second test pulse (P2: 50 ms duration) with an interpulse interval of 20 ms at holding potentials of -100, -80, and -60 mV, respectively. H. Kinetics for the development of inactivation of TTX-R Na.+ channels at VHs of -60 mV (open circles), -80 mV (closed circles), and -100 mV (open squares) in small- (a) and medium-sized (b) DiI-positive neurons. The P2/P1 ratio of TTX-R INa was plotted against the duration of the conditioning prepulse. The points and error bars represent the mean and SEM from seven experiments for small- and medium-sized DiI-positive neurons, respectively. The continuous lines represent the best fits using a double exponential function. I. The mean values of τfast (a) and Afast (b) at different VHs of a two-pulse protocol in small- (open circles) and medium-sized (closed circles) DiI-positive neurons. The points and error bars represent the mean and SEM from seven small- and seven medium-sized DiI-positive neurons. Notably, τfast values were not related to VH in both types of DiI-positive neurons. *; p < 0.05, **; p < 0.01, n.s; not significant (unpaired t-test)

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