大脑皮层神经元NMDA受体的单通道特性

本文用膜片箝技术对机械分离培养的大鼠大脑皮层神经元胞体上的ＮＭＤＡ受体的单通道特性进行了研究，实验用细胞贴附和内面向外两种形式记录单离子通道的活动。电极液内含有ＮＭＤＡ或Ｌ－门冬氨酸时，在皮层神经元上常见电导为３５ｐＳ的离子通道。通道对Ｎａ＋，Ｋ＋非选择性通透，对Ｃｌ－不通透，其平均开放时间和开放概率随超极化程度增大而降低。开放、关闭时间及ｂｕｒｓｔ时程的分布直方图均需双指数拟合。Ｍｇ２＋以电压和浓度依赖性的方式减小通道开放时间，ＡＰＶ能阻断通道活动，温度降低使通道开放时间延长及电流幅度减小。本文结果表明大脑皮层神经元上ＮＭＤＡ受体通道活动自身具有电压依赖性，因此提示ＮＭＤＡ受体通道的正常功能活动可能依赖于某些细胞内调控过程的存在。

SINGLE CHANNEL PROPERTIES OF NMDA RECEPTORS IN CORTICAL NEURONS

The cell-attached and inside-out configurations of the patch-clamp techniques were used to investigate single channel properties of NMDA receptors in cultured intact neurons mechanically isolated from rat cereberal cortex. Recordings were made in Mg2 -free solutions. A channel, with a conductance of 35 pS was studied in detail with either NMDA or L-aspartate in the patch pipette. NMDA channels were permeableic Na and K , but not to Cl-, the mean open times and open probabilities of these channels were decreased with increasing hyperpolarization. Distributions for the open times, closed times and burst durations required two-component fits. Channel openings were suppressed by APV. When Mg2 was included in the pipette, the mean open times were significantly diminished in a concentration- and voltage- dependent manner. Decreasing the bath temperature prolonged channel open times and decreased current amplitudes. The results indicate that there is an intrinsic voltage dependence of NMDA channel kinettes in the intact neurons, suggesting that the normal function of the NMDA channel may be dependent on some intracellular biochemical processes.