Exclusive potassium dependence of the membrane potential in cultured mouse oligodendrocytes.
Membrane potential, conductance, and intracellular potassium concentration were measured in oligodendrocytes in 3- to 10-week-old cultures of embryonic mouse spinal cord. After intracellular recording the cells were first injected with Lucifer Yellow and then stained by immunofluorescence using rhodamine-labeled monoclonal antibody 01 specific for oligodendrocyte cell surfaces. The membrane potential of these identified oligodendrocytes was in mV -66 +/- 4.3 SD; it could be reversibly reduced almost to zero by the addition of ouabain. Changes in external K+ but not Na+, Ca++, or Cl- changed the membrane potential. A 10-fold increase in extracellular potassium concentration ([K+]0) depolarized the cell by about 52 mV. This is less than the 61 mV predicted by the Nernst equation for a K+ electrode assuming a constant intracellular potassium concentration ([K+]i). However, when [K+]i was measured with an ion-selective electrode during the increase in [K+]0 it was found to rise. The Nernst equation for K+ accurately predicts the oligodendrocyte membrane potential when the increase in [K+]i is taken into account. Oligodendrocytes may be described as accurate K+ electrodes with a variable reference solution.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009457:Neuroglia / Q000502:physiology*; D009836:Oligodendroglia / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology
D002712:Chlorides; D010042:Ouabain; D012964:Sodium; D011188:Potassium; D002118:Calcium