ISSN:
1432-2013
Keywords:
Glia
;
Retina
;
Müller cells
;
Ion channels
;
Potassium clearance
;
Rabbit
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract There is ample evidence that retinal radial glial (Müller) cells play a crucial role in retinal ion homeostasis. Nevertheless, data on the particular types of ion channels mediating this function are very rare and incomplete; this holds especially for mammalian Müller cells. Thus, the whole-cell variation of the patch-clamp technique was used to study voltage-dependent currents in Müller cells from adult rabbit retinae. The membrane of Müller cells was almost exclusively permeable to K+ ions, as no significant currents could be evoked in K+-free internal and external solutions, external Ba2+ (1 mM) reversibly blocked most membrane currents, and external Cs+ ions (5 mM) blocked all inward currents. All cells expressed inwardly rectifying channels that showed inactivation at strong hyperpolarizing voltages (≥ −120 mV), and the conductance of which varied with the square root of extracellular K+ concentration ([K+]e). Most cells responded to depolarizing voltages (≥ −30 mV) with slowly activating outward currents through delayed rectifier channels. These currents were reversibly blocked by external application of 4-aminopyridine (4-AP, 0.5 mM) or tetraethylammonium (TEA, 〉 20 mM). Additionally, almost all cells showed rapidly inactivating currents in response to depolarizing (≥ −60 mV) voltage steps. The currents were blocked by Ba2+ (1 mM), and their amplitude increased with the [K+]e. Obviously, these currents belonged to the A-type family of K+ channels. Some of the observed types of K+ channels may contribute to retinal K+ clearance but at least some of them may also be involved in regulation of proliferative activity of the cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374670
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