下丘脑神经元NMDA受体通道特性研究

Properties of NMDA receptor channel in hypothalamic neurons

目的通过对正常和缺氧条件下N-甲基-D-天冬氨酸(NMDA)受体通道特性进行研究,探讨下丘脑神经元缺氧损伤的机理,为临床防治脑缺血/缺氧损伤提供实验依据。方法取材于新生SD大鼠下丘脑视前区/下丘脑前区(PO/AH)神经元,应用膜片钳单通道记录技术对缺氧和非缺氧两种状态下NMDA受体特性进行研究,观察其在缺氧和非缺氧条件下的翻转电位、电流幅度、电导特性的变化。结果神经元缺氧后其通道内向电流幅值由平均(4.501±0.980) pA(n=20,40 mV)上升为(6.000±1.750) pA(n=16,40 mV),优势电导由非缺氧组的(45.693±1.850) pS (n=16)上升为(60.206±1.750) pS(n=10),而翻电位极为接近。结论缺氧是使NMDA受体通道过度激活和Ca2+大量内流的一外因条件。神经元缺氧时,同一钳制电压下其内向电流幅度明显高于对照组,优势电导也有明显上升,可以解释为缺氧引起了神经元Ca2+超载,从而介导了细胞的损伤和死亡。

Objective To probe into the mechanism of hypothalamic neuron damage after anoxia and provide evidence for preventing and curing anoxic/ischemic damage by studying the effect of anoxia on the properties of N-methyl-D-aspartate (NMDA) receptor channel in hypothalamic neurons in SD rats. Methods The neurons from preoptic area and anterior hypothalamus (PO/AH) in new-born SD rats were used to study NMDA receptor channel properties through the cell-attached configurations of the patch clamp technique under normal and anoxia conditions, followed by observing the changes in reversal potential, current amplitude and conductance. Results The mean inward current amplitude and the predominant conductance rose from (4.501±0.980) pA(n=20, 40 mV), (45.693±1.850) pS(n=16) to (6.000±1.750) pA(n=16, 40 mV), (60.206±1.750) pS(n=10), respectively, after anoxia of neurons; but the reversal potentials showed few changes compared with pre-anoxia. Conclusion Anoxia contributes exteriorly to the over-activation of NMDA receptors and thus radical inward current of Ca2+. Under neurons anoxia, the inward current amplitude and the predominant conductance are both evidently higher than in control group. In this course, anoxia may induce the Ca2+ surcharge within neurons and thus mediate neurons into injury and death.