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Updated: Aug 18, 2026
Immunohistochemical and Calcium Imaging Methods in Wholemount Rat Retina
Published on: October 13, 2014
Na(+) currents through Ca(2+) channels in human retinal glial (Müller) cells
A Bringmann1, B Biedermann, F Faude
1Department of Neurophysiology, University of Leipzig, Paul Flechsig Institute of Brain Research, Leipzig, Germany. bria@server3.medizin.uni-leipzig.de
Purpose:
To detect the presence of voltage-gated Ca(2+) channels in the plasma membranes of freshly isolated Müller glial cells from the human retina and their modulation by GABA(B) receptor agonists.
Methods:
Whole cell voltage-clamp recordings were made to study Ca( 2+), Ba(2+), and Na(+) currents through voltage-gated Ca(2+) channels.
Results:
The vast majority of the investigated cells displayed no resolvable currents through Ca(2+) channels when Ca(2+) ions (2 mM) were present in the extracellular solution. Small-amplitude inwardly directed currents ( approximately 0.6 pA/pF) were detected when Ba(2+) ions (20 mM) were used as charge carrier. However, when Na(+) ions were used as charge carrier in divalent cation-free external solution, currents of large amplitudes ( approximately 7.5 pA/pF) through voltage-gated Ca(2+) channels were detected. Human Müller cells displayed currents through both transient, low voltage-activated Ca(2+) channels and long-lasting, high voltage-activated channels. The Na(+) fluxes through low voltage-activated Ca( 2+) channels were inhibited in a voltage-independent manner in the presence of GABA(B) receptor agonists.
Conclusions:
Human Müller glial cells express different kinds of voltage-gated Ca(2+) channels in their plasma membranes that can be activated only under certain physiological or pathophysiological conditions. The record of Na(+) fluxes in divalent cation-free solutions may be a technique to detect the presence of "hidden" voltage-gated Ca(2+) channels in Müller glial cells.
