Characterization of a voltage-gated K+ channel that accelerates the rod response to dim light

Neuron. 1989 Nov;3(5):573-81. doi: 10.1016/0896-6273(89)90267-5.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Barium / metabolism
  • Cadmium / pharmacology
  • Cesium / pharmacology
  • Electrophysiology
  • Extracellular Space / metabolism
  • Ion Channel Gating*
  • Light*
  • Photoreceptor Cells / physiology*
  • Potassium / physiology
  • Potassium Channels / physiology*
  • Time Factors
  • Urodela


  • Potassium Channels
  • Cadmium
  • Cesium
  • Barium
  • Potassium