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. 2017 Jun 13;10:181. doi: 10.3389/fnmol.2017.00181

Figure 2.

Figure 2

In nociceptor-like DRG neurons IM is outward at resting-to-threshold potential range (A). Upper, Typical voltage-clamp perforated patch recordings of IM from a nociceptor-like DRG neuron (see Methods, representative of 18/18 neurons). A family of currents was evoked by a series of 1 s, 5 mV hyperpolarizing voltage steps from a holding potential of −20 mV (voltage protocol is shown in inset). The peak current response obtained by stepping to −50 mV is shown at the bottom. The IM relaxation was fitted with a bi-exponential line (red), which was extrapolated to the beginning of the voltage step. IM amplitudes were measured as the differences between the instantaneous peak currents at command onset and the steady-state currents just before command offset (dotted line). (B) Averaged leak-subtracted peak I-V characteristics of IM recorded from nociceptor-like DRG neurons (n = 18), calculated as described in Methods. ns—not significant; one-way ANOVA comparison between the current values obtained at −90 mV (zero current level) to currents at other command voltages. Note, significant outward current at −60 mV. Insets show box charts and individual values of resting membrane potentials (VRest, n = 10) and action potential thresholds (VTh, n = 9), obtained from current clamp perforated patch recordings (see Methods). The middle line of the box charts represents the mean; the box represents 25 ~ 75% percentiles and caps delineate range within 1.5 interquartile range. The mean (in mV) is aligned to its values on the x-axis. The shadowed area indicates the range of membrane potentials between resting potential and threshold. (C) Mean ± SEM of IM activation curves (g/gmax) fitted using the Boltzmann equation (see Methods) shows the onset of activation at −60 mV (ns—not significant; one-way ANOVA comparison between the conductance values obtained at −90 mV (zero conductance level) to conductances at other command voltages) and V1/2 at −42 mV. The shadowed area indicates the range of membrane potentials between resting potential (mean, VRest) and threshold (mean, VTh) taken from (B), insets.