Figure 6
From: Jedi-1 deficiency increases sensory neuron excitability through a non-cell autonomous mechanism
Voltage gated sodium channels have altered properties in DRG neurons isolated from Jedi-1 KO mice. Whole cell patch clamp electrophysiology was used to record voltage-gated sodium channel currents from small diameter wild-type (WT) and Jedi-1 knockout (KO) DRG neurons. (A) The upper trace shows two superimposed currents from the same cell evoked by a voltage step from −100 mV to 0 mV. Replacement of extracellular NaCl with TEA-Cl abolished the fast inward current confirming it was due to activation of voltage-gated sodium channels. The peak current density evoked by a voltage step to 0 mV was not significantly different between genotypes. Each point is from an individual cell, box indicates median, 25% and 75% of the distribution, whisker indicate standard deviation of the mean. (B) Current-voltage relationship for wild type (WT) and knockout (KO) neurons. The upper panel shows an example of the stimulus protocol and sodium currents from a representative neuron. The lower panel plots mean peak current density against the test potential. (C) Normalized inactivation curves (left two curves) and activation curves (right two curves) for wild type and knockout neurons are superimposed. The inset cartoons depict the voltage protocols: inactivation was produced by a series of 500ms steps (−120 mV to 0 mV) prior to a 50ms test pulse to 0 mV. Peak current amplitude produced by the test pulse was normalized to the largest current and plotted against the voltage of the 500ms conditioning pulse. Solid curves show the fit with a double Boltzmann function. Activation curves were derived from the same data used to produce the current voltage-relationship in panel (B) (see methods for more detail). Solid curves show the fit with a Boltzmann function. The “window current” is shown on an expanded scale in the dashed box to the right.
