Figure 1

Effect of hypotonicity on TTX-S current in TG neurons. A. Plot of current densities as function of hypotonic stimuli shows that the increase of TTX-S current was conspicuous at the largest osmotic gradient. B. The typical recordings show that TTX-S current was increased by hypotonicity. Upper: total sodium current, middle: TTX-R current obtained during application of 300nM TTX, below: TTX-S current obtained by subtracting TTX-R current from total. C. Comparison of voltage-current relationship (I-V curve) for TTX-S current in isotonic and hypotonic solution. D. TTX-S current was converted to a conductance and fitted to a Boltzman function. The mid-point of activation (V_0.5) was significantly more negative in hypotonic than in isotonic solution (-41.17 ± 1.09 mV vs. -34.41 ± 2.16 mV, n = 9, pared t-test, P < 0.05). However, the slope factor (k) was not significantly different between isotonic and hypotonic solution (3.54 ± 0.23 vs. 3.29 ± 0.89, n = 9, pared t-test, P > 0.05). E. Unlike G-V curve, the inactivation-voltage curve did not shift before and during hypotonic treatment. V_0.5 were -69.66 ± 2.17 mV and -71.55 ± 3.21 mV (n = 10, paired t-test, P > 0.05), k were -9.86 ± 1.81 and -11.25 ± 1.03 (n = 10, paired t-test, P > 0.05) for 300mOsm and 260mOsm respectively.