Outwardly rectifying K+ channels display clustering in guinea pig retinal Muller cells

The cell-attached configuration of the patch-clamp technique was used to ch aracterize the outward currents in acutely isolated Muller cells from the g uinea pig retina. Sixty-five of 353 patches displayed macroscopic, outwardl y rectifying currents due to depolarizing voltage steps. Single channel tra nsitions were found in only two patches. The remaining patches did not reve al any voltage-dependent currents. Tail current analysis revealed a reversa l potential close to the resting membrane potential. The currents disappear ed if internal K+ was replaced by Cs+ in inside-out patches. From these res ults we conclude that guinea pig Muller cells possess voltage-dependent Kchannels that are distributed in clusters. (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.