大鼠大脑皮层神经元单离子钾通道门控动力学

GATING KINETICS OF SINGLE POTASSIUM CHANNEL OF CULTURED RAT CEREBRAL NEURON

采用膜片钳制技术,对新生大鼠大脑皮层神经元作了细胞贴附和内膜向外两种模式的单通道电流记录。通道开放和关闭事件的转换过程为一随机过程,开关时间服从指数分布。细胞膜单离子通道的时间常数和对离子通透性接近的构象组成构象集合态。由残差法获得模型参数初值,由非线性最小二乘法获得修正值。新生大鼠大脑皮层神经元在-40mV钳制电位和电极内外对称高钾溶液下,细胞贴附和内膜向外的两种膜片钳制模式的单通道电流的动力学特征有明显差异。通道开放时间分布接近一状态分布。细胞贴附时的通道平均开放时间为2.53ms。内膜向外时的通道平均开放时间为2.04ms。关闭时间分布接近三状态分布,细胞贴附时通道平均关闭时间为3.36ms,内膜向外时通道的平均关闭时间为7.58ms。细胞贴附下,通道关闭时主要处于第一和第二关闭态;内膜向外下,通道关闭时主要处于第一关闭态。经初值估计和参数修正,得到各状态间的转移概率密度常数。

Single potassium channel current of cultured rat cerebral neuron were recorded with cell-attached and inside-out patch clamp. The mixed kinetic parameters and the transition rates of aggregative conformation states were identified by residual error and nonlinear least square method. The kinetic characteristics of cell-attached patch on cultured cerebral neuron of new-born rat was different from that of inside-out patch at holding potential-40 mV with symmetric potassium solution in bath and pipette. The open time probability distribution function obeyed one state distribution and the mean open-time in cell-attached mode was 2.53 ms while in inside-out mode was 2.04 ms. The closed-time probability distribution function obeyed three states distribution and the mean closed-time was 3.36 ms in cell-attached mode but was 7.58 ms in inside-out mode. The transition rates of the four states were identified by nonlinear least square method. The channel mainly sojourned at the first and the second closed state in cell-attached mode, but mainly sojourned at the first closed state in inside-out mode duriog closed period.