Existence of inward potassium currents in adult human oligodendrocytes.

We report the first measurements of single channel currents in cultured adult human oligodendrocytes, obtained postmortem. The channels selectively pass potassium inwardly and possess properties which would be suitable for a physiological role for oligodendrocytes in the human brain as part of a regulatory mechanism for maintenance of extracellular potassium concentration near active neurons. These properties include a long mean open time near normal resting potential and a marked dependence of membrane depolarization to increase the channel open time which could be an important factor when the driving force for inward potassium movement was small. Furthermore, the properties of these potassium channels are remarkably similar to those of channels previously observed in adult bovine oligodendrocytes, which supports the use of animal data to describe function in the human brain.