INTERNAL NA-OOCYTES( AND MG2+ BLOCKADE OF DRK1 (KV2.1) POTASSIUM CHANNELS EXPRESSED IN XENOPUS)

Delayed rectifier potassium channels were expressed in the membrane of Xenopus oocytes by injection of rat brain DRK1 (Kv2.1) cRNA, and curr ents were measured in cell-attached and inside-out patch configuration s. In intact cells the current-voltage relationship displayed inward g oing rectification at potentials > +100 mV. Rectification was abolishe d by excision of membrane patches into solutions containing no Mg2+ or Na+ ions, but was restored by introducing Mg2+ or Na+ ions into the b ath 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) respectiv ely. Increasing extracellular potassium concentration reduced the degr ee of rectification of intact cells. It is concluded that inward going rectification resulting from voltage-dependent block by internal cati ons can be observed with normally outwardly rectifying DRK1 channels.