Quinine blockade of currents through Ca2+-activated K+ channels in bovine chromaffin cells.

摘要: 1. The blocking action of quinine Ca2+-activated K+ channels was studied in excised inside-out patch recordings from cultured bovine chromaffin cells. Under normal ionic conditions (160 mM-K+ inside, 154 mM-Na+ outside), the unitary conductances measured between -20 and +40 mV were 95 210 pS. 2. Quinine applied on intracellular side membrane micromolar concentrations chopped currents into bursts brief openings. These 'flickery bursts' appear to arise discrete unblocking transitions. 3. Open closed times within such flickery exponentially distributed suggesting a simple reaction an open channel. 4. rate varied linearly with concentration (rate coefficient 1.6 x 10(6) M-1 s-1). high (greater than 5000 s-1) essentially independent concentration. 5. voltage dependent increased hyperpolarization which suggests that acts predominantly or exclusively extracellular membrane. appeared be potential. 6. probability state not altered by indicating did interfere directly gating process. 7. total current carried ions reduced only marginally (less 10%) even at (1.5 mM). Moreover reduction also independent. 8. is clearly very poor blocker. Poor block occurs, however, because brevity periods but presumably channel can when it blocked. Only opening (p) 0.85), i.e. channel's gate open, reduce appreciably.