AN ADENOSINE-TRIPHOSPHATE (ATP)-SENSITIVE K-GATED BY INTRACELLULAR ATP AND VOLTAGE - A NOVEL CHANNEL GATING MECHANISM( CHANNEL OF RAT NEOCORTICAL NEURONS IS BI)

To determine whether the adenosine triphosphate (ATP)-sensitive K+ (K- ATP) channels, which are suggested to be mainly regulated by intracell ular ATP or other kinds of triphosphate nucleotides, are gated by memb rane potentials (Vm), single K-ATP channel currents were studied on in side-out membrane patches of neurons acutely dissociated from Sprague- Dawley rat neocortex. The K-ATP channels recorded have a unitary condu ctance from 96.97 +/- 5.32 pS (n = 11) at potentials of similar to 10- 60 mV to 98.31 +/- 3.26 pS (n = 11) at similar to -10 to -60 mV. Besid es being inhibited by cytoplasmic ATP, channel kinetics was also affec ted by Vm. Open- and closed-time histograms were well fitted by 2 expo nentials, suggesting that the channels have 2 open and closed states. Mean open time (tau(om)), open probability increased while mean closed time (tau(cm)) decreased with depolarization. The fitted equations of the relationships between Vm and those kinetic parameters may be desc ribed as: tau(om) = -159.26lnVm + 403.64, P-0 = -0.01Vm(2) + 0.08Vm 0.87 and tau(cm) = 0.17Vm(3) - 2.5Vm(2) + 10.35Vm - 7.68, respectively . We suggest that the K-ATP channels be bi-gated by both intracellular ATP and membrane potentials. This property of the neuronal K-ATP chan nels may be related to their pathophysiological functions.