Fig. 4.
Voltage-dependent activation of stromatoxin-1 (ScTx1)-sensitive KV currents in guinea pig DSM cells. A: representative recording of the effect of ScTx1 on the whole cell KV current elicited by a short (400 ms) voltage-step protocol (top). ScTx1 (100 nM) significantly decreased the voltage step-induced whole cell KV current. ScTx1-sensitive current was obtained after subtraction of the remaining whole cell current from the control current. The scale bar applies to all recordings. B: the current-voltage relations show that ScTx1 (100 nM) decreased voltage-dependent whole cell KV current in guinea pig DSM cells (n = 12; N = 9). *P < 0.05; **P < 0.005; ***P < 0.001. The current-voltage relation of the subtracted ScTx1-sensitive current is also shown. C: steady-state activation curves of the KV current in the absence (control) or presence of 100 nM ScTx1 (ScTx1-insensitive current). Data were obtained from the current recordings shown in A. The tail currents recorded after stepping back to −40 mV for 800 ms were used to build the normalized conductance (G/Gmax) curve. The curves were fitted using a single-component Boltzmann equation. The steady-state activation curve of the ScTx1-sensitive current is also shown. Values are means ± SE. All experiments were performed in the presence of the selective BK channel inhibitor paxilline (100 nM).