Role of glial K(+) channels in ontogeny and gliosis: a hypothesis based upon studies on Müller cells

Glia. 2000 Jan 1;29(1):35-44. doi: 10.1002/(sici)1098-1136(20000101)29:1<35::aid-glia4>3.0.co;2-a.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Cell Differentiation / physiology
  • Cell Division / physiology
  • Gliosis / metabolism
  • Gliosis / physiopathology*
  • Humans
  • Large-Conductance Calcium-Activated Potassium Channels
  • Membrane Potentials / physiology
  • Neuroglia / metabolism*
  • Potassium / metabolism
  • Potassium Channels / metabolism
  • Potassium Channels / physiology*
  • Potassium Channels, Calcium-Activated*
  • Potassium Channels, Inwardly Rectifying*
  • Retina / cytology
  • Retina / metabolism*
  • Retina / physiology

Substances

  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Potassium Channels, Inwardly Rectifying
  • Potassium