Two types of potassium current in rabbit cultured Schwann cells.
Voltage-gated outward currents were studied in rabbit cultured Schwann cells with the 'whole-cell' configuration of the patch-clamp method. Four components of such currents were identified. The first, which was abolished by replacement of the external chloride ions by the large impermeant anion gluconate, was identified as a chloride current. The second and third were identified as potassium currents. One type of potassium current was reduced substantially by either 4-aminopyridine (4-AP) or tetraethylammonium ion (TEA). Its sensitivity to blocking by 4-AP was highly voltage-dependent: the equilibrium dissociation constant (K) was threefold greater when measured at +10 mV than when measured at -40 mV (where it was about 80 microM). The second type of potassium current was relatively insensitive to 4-AP, but was blocked by TEA. The TEA sensitivity of the two types of potassium currents was similar and displayed no obvious voltage-dependence (K approximately 200 microM). The fourth component of current was not reduced by 4-AP or TEA at concentrations less than 10 mM. Whether or not this last component is a potassium current is unclear.
Howe
J R
JR
Department of Pharmacology, Yale University, New Haven, Connecticut 06510.
Ritchie
J M
JM
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D007473:Ion Channels / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials; D011817:Rabbits; D012583:Schwann Cells / Q000502:physiology*; D012584:Sciatic Nerve / Q000502:physiology
D007473:Ion Channels