Voltage-dependent K+ currents in guinea pig Müller (glia) cells show different sensitivities to blockade by Ba2+.
The effect of externally applied Ba2+ and Na+ on K+ currents was investigated by means of whole-cell patch-clamp in isolated and in situ Müller cells from guinea pig retina. Müller cells express a typical set of K+ currents, i.e. an ohmic current, an inactivating inward current (IK(IR)), a delayed rectifier (IK(DR)) and an inactivating outward current (IK(A)). Inactivation of the inward current did not occur when extracellular Na+ was replaced by choline. When administered in increasing concentrations, Ba2+ blocked these K+ currents in a typical sequence: the ohmic current and IK(A) were most sensitive, followed by IK(IR), whereas IK(DR) was not completely blocked even in 1 mM Ba2+. The differential sensitivity of Müller cell K+ currents to external Ba2+ may be a tool which can be used to improve our understanding of the Müller cell response to physiological stimulation of the retina.
Reichelt
W
W
Carl-Ludwig-Institute of Physiology, University of Leipzig, FRG.
Pannicke
T
T
D000818:Animals; D001464:Barium / Q000378:metabolism / Q000494:pharmacology*; D002469:Cell Separation; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005260:Female; D006168:Guinea Pigs; D009457:Neuroglia / Q000502:physiology*; D009994:Osmolar Concentration; D011188:Potassium / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D012160:Retina / Q000166:cytology / Q000502:physiology*
D001464:Barium; D011188:Potassium