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Elevated potassium shortens action potential duration by altering outward currents in chick dorsal root ganglia
1Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110.
Abstract:
Dissociated embryonic chick dorsal root ganglion (DRG) neurons maintained in culture exhibit a mixed Na+/Ca2+ action potential. The characteristic "shoulder" on the repolarizing phase is due to the relatively prolonged inward Ca2+ current. DRG neurons grown in an elevated K+ medium (25 versus. 5 mM) lack the plateau phase of the action potential. Voltage-clamp analysis showed that this plastic change in action potential duration is not due to the loss of the inward Ca2+ current but is partly due to the appearance of a Ca2(+)-dependent, 4-aminopyridine-(4-AP)-sensitive transient outward current. Faster activation of the purely voltage-dependent delayed rectifier outward current also contributes to the rapid repolarization observed in neurons cultured in elevated K+ medium.