Properties of retinal glial cell potassium channels.
The patch-clamp technique was used to investigate the nature of potassium channels localised in the end-feet-membrane of Müller (glial) cells of the chicken retina. Two different preparations were used to examine ion channels in this membrane area. The ion channels were investigated either in eye-cup preparation, leaving the retina intact, or in isolated endfeet. In both preparations the ion channels showed identical characteristics. We found three K+ channels that could be distinguished by their electrical properties. In the inside-out configuration, in a standard bathing solution (6 mM potassium) with the pipette solution containing 100 mM potassium, these channels showed conductances of 15 pS, 29 pS and 68 pS. Whereas the 29 pS-channel was not voltage-dependent, the 15 pS- and 68 pS-channel showed significant voltage-dependence of the open-state probability. By membrane depolarisation the open-state probability of both channels types increased. The resting membrane potential of the glial cells was estimated to be about -80 mV, which is, as result of the high selectivity of the glial membranes for K+, more negative than that of retinal neurons.
Brand
S
S
Institut für Zoophysiologie (230), Universität Hohenheim, Stuttgart, Germany
Hanke
W
W
D000818:Animals; D009457:Neuroglia / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D012160:Retina / Q000502:physiology*; D013997:Time Factors
D015221:Potassium Channels