Sivaramakrishnan S, Bittner G D, Brodwick M S
Department of Zoology, College of Pharmacy, University of Texas, Austin 78712.
J Gen Physiol. 1991 Dec;98(6):1161-79. doi: 10.1085/jgp.98.6.1161.
Membrane potential changes that typically evoke transmitter release were studied by recording intracellularly from the excitor axon near presynaptic terminals of the crayfish opener neuromuscular junction. Depolarization of the presynaptic terminal with intracellular current pulses activated a conductance that caused a decrease in depolarization during the constant current pulse. This conductance was identified as a calcium-activated potassium conductance, gK(Ca), by its disappearance in a zero-calcium/EGTA medium and its block by cadmium, barium, tetraethylammonium ions, and charybdotoxin. In addition to gK(Ca), a delayed rectifier potassium conductance (gK) is present in or near the presynaptic terminal. Both these potassium conductances are involved in the repolarization of the membrane during a presynaptic action potential.
通过在小龙虾开肌神经肌肉接头突触前终末附近的兴奋性轴突内进行细胞内记录，研究了通常引起递质释放的膜电位变化。用细胞内电流脉冲使突触前终末去极化，激活了一种电导，该电导在恒定电流脉冲期间导致去极化减小。通过其在零钙/乙二醇双四乙酸（EGTA）培养基中消失以及被镉、钡、四乙铵离子和大蝎毒素阻断，这种电导被确定为钙激活钾电导gK(Ca)。除了gK(Ca)，突触前终末内或其附近还存在延迟整流钾电导（gK）。这两种钾电导都参与突触前动作电位期间膜的复极化过程。
