Figure 1.
Progesterone inhibits voltage-gated potassium currents. (A) Representative traces of whole-cell voltage clamp recordings of potassium currents evoked by a series of 100 ms steps in 10 mV increments from −20 to +50 mV (from a resting potential of −80 mV) in the absence (Left) or presence (Right) of 50 μM progesterone. (B) Current/voltage plot of whole-cell potassium currents in the presence or absence of progesterone. (C) Plot of the fractional block (%) by progesterone as a function of voltage, indicating the effects of progesterone are voltage-independent. (D) The effects of progesterone were concentration-dependent. Pregnenolone and allopregnanolone did not block potassium currents, whereas the nifedipine exhibited significant block.