Analysis of the K+ current profile of mature rat oligodendrocytes in situ.
Previous studies have reported that mature oligodendrocytes (OLGs) in vitro display various voltage-dependent K+ currents while in situ OLGs show only voltage-independent K+ currents. Given this discrepancy and the lack of information on myelinating OLG ion channel expression in situ, we characterized mature OLG currents in myelinating corpus callosum slices from 17 to 36-day old rats. OLGs were recorded in cell-attached and whole-cell patch-clamp configurations, displayed morphology typical of mature OLGs, and stained positive for myelin basic protein. OLGs displayed large voltage-independent currents that decayed during the voltage pulse and small voltage-activated outward currents. The latter were blocked by TEA, activated between -40 and -50 mV, and decayed slowly. The former were composed of large voltage-independent, time-dependent Ba2+ (1 mM)-sensitive currents, and voltage-dependent Cs+ (5 mM) and Ba2+ (100 mM)-sensitive currents that reversed near the K+ equilibrium potential and inactivated at hyperpolarized potentials, identifying them as inwardly rectifying K+ currents. Inwardly rectifying single-channel K+currents could be recorded in the cell-attached configuration. The estimated single-channel slope conductance was 30 pS. The steady-state open probability was voltage-dependent and declined from 0.9 to 0.5 between -80 and -150 mV. Overall, mature OLGs in situ possess time- and also voltage-dependent K+ currents, which may facilitate clearance of K+ released during axonal firing.
Gipson
K
K
Interdepartmental Neuroscience Graduate Program, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06520-8082, USA.
Bordey
A
A
D000818:Animals; D001464:Barium / Q000378:metabolism / Q000494:pharmacology; D002586:Cesium / Q000378:metabolism / Q000494:pharmacology; D003337:Corpus Callosum / Q000187:drug effects / Q000502:physiology*; D004553:Electric Conductivity; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009836:Oligodendroglia / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D019789:Tetraethylammonium / Q000378:metabolism / Q000494:pharmacology
D015221:Potassium Channels; D002586:Cesium; D001464:Barium; D019789:Tetraethylammonium