Skip to main content
Figure 9 | Molecular Pain

Figure 9

From: Sodium-calcium exchangers in rat trigeminal ganglion neurons

Figure 9

Prolonged inactivation kinetics in voltage-dependent Na+channels caused by NCX blockage. (A and B) I-V relationships were obtained by plotting the values of peak current against applied membrane potentials, which cell size accounted by normalizing for measured capacitance and expressing current amplitudes in terms of current densities (pA/pF). Cell size was 22–31 μm. Vh was −70 mV. (A) Inward currents (open circles) were inhibited by 1.0 μM TTX (filled circles) under both the physiological condition with 44 nM [Ca2+]i (black circles), and the [Ca2+]i-overloaded condition with 26 μM [Ca2+]i (red circles), indicating that currents were voltage-dependent Na+ currents (total INa). (B) A cocktail of NCX inhibitors (3.0 μM KB-R7943, 0.03 μM SEA0400, and 0.5 μM SN-6) (filled circles) had no significant effect on the peak amplitude of total INa in either the physiological (black circles) or [Ca2+]i-overloaded (red circles) condition. (C) Comparison of the time constant of inactivation (τ) for total INa with (filled circles) or without (open circles) the cocktail of NCX inhibitors under the physiological (black circles) and [Ca2+]i-overloaded (red circles) conditions, at membrane potentials ranging from −30 mV to +30 mV. (Inset in C) Total INa in the [Ca2+]i-overloaded condition (grey lines), evoked by a voltage pulse of up to −20 mV from a Vh of −70 mV, was well fitted by a single exponential function (black line). An inward current at −20 mV showed rapid inactivation without the cocktail of NCX inhibitors, while the NCX inhibitors slowed the inactivation kinetics. Data points (C) illustrate τ as a function of each membrane potential. Data points (A to C) represent mean ± S.D. of the number of tested cells. Statistically significant differences in current amplitude values or τ of total INa inactivation are indicated.

Back to article page