Characterization of a voltage-gated K+ channel that accelerates the rod response to dim light.
In this study a K+ current, IKx, in isolated salamander rod photoreceptors was characterized and its role in shaping small photovoltages was examined. IKx is a standing outward current of about 40 pA at -30 mV that deactivates slowly when the cell is hyperpolarized (tau max = 0.25 s). The voltage and time dependence of IKx are similar to that of M-current, but IKx can be distinguished from M-current because it is not suppressed by acetylcholine and is "blocked" by external Ba2+ in a surprising manner: the activation range of IKx is shifted strongly in the positive direction. Using current-clamp recordings and a computer simulation of the photo-response, we show that IKx figures prominently in setting the dark resting potential and accelerates the voltage response to small photocurrents.
Beech
D J
DJ
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle 98195.
Barnes
S
S
D000818:Animals; D001464:Barium / Q000378:metabolism; D002104:Cadmium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D015640:Ion Channel Gating; D008027:Light; D010786:Photoreceptor Cells / Q000502:physiology*; D011188:Potassium / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D013997:Time Factors; D014562:Caudata
D015221:Potassium Channels; D002104:Cadmium; D002586:Cesium; D001464:Barium; D011188:Potassium