title: Internal Na+ and Mg2+ blockade of DRK1 (Kv2.1) potassium channels expressed in Xenopus oocytes. Inward rectification of a delayed rectifier.
abstract: Delayed rectifier potassium channels were expressed in the membrane of Xenopus oocytes by injection of rat brain DRK1 (Kv2.1) cRNA, and currents were measured in cell-attached and inside-out patch configurations. In intact cells the current-voltage relationship displayed inward going rectification at potentials > +100 mV. Rectification was abolished by excision of membrane patches into solutions containing no Mg2+ or Na+ ions, but was restored by introducing Mg2+ or Na+ ions into the bath solution. At +50 mV, half-maximum blocking concentrations for Mg2+ and Na+ were 4.8 +/- 2.5 mM (n = 6) and 26 +/- 4 mM (n = 3) respectively. Increasing extracellular potassium concentration reduced the degree of rectification of intact cells. It is concluded that inward going rectification resulting from voltage-dependent block by internal cations can be observed with normally outwardly rectifying DRK1 channels.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: A N
authors.initials: AN
authors.lastname: Lopatin
authors.forename: C G
authors.initials: CG
authors.lastname: Nichols
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology; D004594:Electrophysiology; D008274:Magnesium / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000096:biosynthesis / Q000187:drug effects*; D051381:Rats; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology*; D014981:Xenopus
chemical_list: D015221:Potassium Channels; D000255:Adenosine Triphosphate; D012964:Sodium; D008274:Magnesium