Effects of brief mechanical stimulation on Hv1NC_VSP activation. (A) Hv1NC_VSP current was elicited by membrane depolarization as in Fig. 2 B and measured in the absence of mechanical stimulation (black) and in the presence of a brief pulse of negative pressure in the pipette (red). The pulse was delivered when the fraction of open channels generated by voltage-dependent activation was still small. See Materials and methods for details. (B) Enlarged view of current traces (I) enclosed in the blue rectangle in A. Pressure traces recorded during stimulation are also shown (P). (C) Hv1 currents were measured as in A, but with the mechanical stimulus delivered when voltage-dependent activation had produced a larger fraction of open channels. (A and C) Inset bar chart indicates the mean relative increase in current measured at the end of the pulse (EP) and the mean residual increase in current measured at the end of the depolarization step (ED). Error bars are SEM (n = 5). (D) Enlarged view of current traces (I) enclosed in the blue square in C and corresponding pressure traces (P). There was no difference in isochronal current at the end of the two traces in A and C (black arrowheads, ED ≈ 0). Red, blue, and gray arrowheads in B and D indicate different components of the effect of mechanical stimulation on Hv1 activation.