Glial heterogeneity in expression of the inwardly rectifying K+ channel, Kir4.1, in adult rat CNS

Previous electrophysiological evidence has indicated that astrocytes and ol igodendrocytes express inwardly rectifying K+ channels both in vitro and in vivo. Here, for the first time, we have undertaken light microscopic immun ohistochemical studies demonstrating the location of one such channel, Kir4 .1, in both cell types in regions of the rat CNS. Some astrocytes such as t hose in the deep cerebellar nuclei, Bergmann glia, retinal Muller cells, an d a subset in hippocampus express Kir4.1 immunoreactivity, but not others i ncluding those in white matter. Oligodendrocytes also express this protein, strongly in perikarya and to a lesser extent in their processes. Expressio n of Kir4.1 in astrocytes and oligodendrocytes would enable these cells to clear extracellular K+ through this channel, whereas nonexpressors might us e other mechanisms. (C) 2000 Wiley-Liss, Inc.