Effect of 1 μM Sar-SP on action potential threshold and firing rate in DRG neurons. Sar-SP reduced the amount of current required to evoke action potential and increased the firing rate in DRG neurons. Experiments were performed using current clamp model. A and B: depolarizing current pulse required to evoke an action potential in a DRG neuron, before (A) and after (B) application of Sar-SP (a = 130 pA, b = 140 pA, c = 80 pA, d = 90 pA). C: effect of Sar-SP on the threshold for action potential generation by depolarizing current pulse (**p < 0.01, paired t-test, n = 6). D and E: firing response of a DRG neuron to a 500 pA depolarizing current pulse (500 ms), before (D) and after (E) application of Sar-SP. F: effect of Sar-SP on firing rate in DRG neurons (***p < 0.001, paired t-test, n = 6).