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Role of glial K + channels in ontogeny and gliosis: A hypothesis based upon studies on Müller cells
Author(s) -
Bringmann Andreas,
Francke Mike,
Pannicke Thomas,
Biedermann Bernd,
Kodal Hannes,
Faude Frank,
Reichelt Winfried,
Reichenbach Andreas
Publication year - 2000
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/(sici)1098-1136(20000101)29:1<35::aid-glia4>3.0.co;2-a
Subject(s) - depolarization , gliosis , membrane potential , biology , electrophysiology , biophysics , neuroglia , neuroscience , microbiology and biotechnology , central nervous system
The electrophysiological properties of Müller cells, the principal glial cells of the retina, are determined by several types of K + conductances. Both the absolute and the relative activities of the individual types of K + channels undergo important changes in the course of ontogenetic development and during gliosis. Although immature Müller cells express inwardly rectifying K + (K IR ) currents at a very low density, the membrane of normal mature Müller cells is predominated by the K IR conductance. The K IR channels mediate spatial buffering K + currents and maintain a stable hyperpolarized membrane potential necessary for various glial‐neuronal interactions. During “conservative” (i.e., non‐proliferative) reactive gliosis, the K IR conductance of Müller cells is moderately reduced and the cell membrane is slightly depolarized; however, when gliotic Müller cells become proliferative, their K IR conductances are dramatically down‐regulated; this is accompanied by an increased activity of Ca 2+ ‐activated K + channels and by a conspicuous unstability of their membrane potential. The resultant variations of the membrane potential may increase the activity of depolarization‐activated K + , Na + and Ca 2+ channels. It is concluded that in respect to their K + current pattern, mature Müller cells pass through a process of dedifferentiation before proliferative activity is initiated. GLIA 29:35–44, 2000. © 2000 Wiley‐Liss, Inc.