Modulation of cloned human neuronal voltage-gated potassium channels (hKv1.1 and hKv2.1) by neurosteroids.

Two voltage-gated potassium channels, hKv1.1 and hKv2.1, were stably expressed in Chinese hamster ovary cells. The effects of neurosteroids, pregnenolone sulfate (PS), 5alpha-pregnan-3alpha-ol-20-one sulfate (5alpha3alphaP), and 5beta-pregnan-3alpha-ol-20-one sulfate (5beta3alphaP), on hKv1.1 and hKv2.1 were studied using the patch-clamp method. PS, 5alpha3alphaP, and 5beta3alphaP shifted current/voltage (I/V) relationship of both channels to the left by about 10 mV. The neurosteroids also increased the current amplitude voltage dependently. The activation time constants (taua) for hKv1.1 and hKv2.1 were voltage dependent and decreased with membrane depolarization. At -20 mV, PS reduced taua for hKv1.1 by 8 ms and 15 ms at 10 and 100 microM respectively. PS also significantly decreased the taua of hKv2.1 by 30 ms (10 microM) and 38 ms (100 microM) at +10 mV. However, only at 100 microM did 5alpha3alphaP or 5beta3alphaP significantly alter the taua of hKv1.1. Neither 5alpha3alphaP nor 5beta3alphaP affected the taua of hKv2.1. Deactivation time constants (taud) were also voltage dependent and, in contrast to taua, taud was prolonged with membrane depolarization. At 100 microM, PS, 5alpha3alphaP, and 5beta3alphaP significantly increased the taud for hKv1.1 but did not affect the taud for hKv2.1.