Ca(2+) channel-mediated currents in retinal glial (Müller) cells of the toad (Bufo marinus).
Whole-cell voltage-clamp recordings were used to detect voltage-gated Ca(2+) channels in freshly isolated retinal glial (Müller) cells of the toad (Bufo marinus). Using Ca(2+) ions (2 mM) as charge carriers (in the presence of 1 mM Mg(2+)), no inwardly directed currents could be observed during the application of depolarizing voltage steps. However, after omitting the divalent cations from the bath solution, large-amplitude inwardly directed currents were evoked that were carried by Na(+) ions, and were mediated by at least two different kinds of Ca(2+) channels, transient low voltage-activated (LVA) channels and sustained high voltage-activated (HVA) channels. While the LVA currents activated at potentials positive to -90 mV and peaked at -40 mV, the HVA currents activated positive to -60 mV and peaked at -20 mV. It is concluded that Müller glial cells of the toad express distinct types of voltage-gated Ca(2+) channels that may be activated, under certain conditions, close to physiological membrane potentials.
Bringmann
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A
Department of Neurophysiology, Paul Flechsig Institute of Brain Research, University of Leipzig, Jahnallee 59, D - 04109, Leipzig, Germany. bria@server3.medizin.uni-leipzig.de
Pannicke
T
T
Reichenbach
A
A
Skatchkov
S N
SN
D000818:Animals; D002024:Bufo marinus; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D015640:Ion Channel Gating; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D012160:Retina / Q000166:cytology / Q000502:physiology*
D015220:Calcium Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying