弱激光对神经元瞬时外向钾通道电流特性的影响

应用全细胞膜片钳技术,研究了急性分离的大鼠海马CA3区锥体神经细胞在波长670 nm、功率5 mW的半导体激光器照射时,其瞬时外向钾通道电流特性。实验发现:弱激光对瞬时外向钾电流I_A有抑制作用,5 min激光抑制作用达到稳定,去极化至+50 mV时抑制百分比为(40.13±5.19)%(n=10);弱激光对I_A的抑制作用呈现电压依赖性和可逆性,对照组、照射组和恢复组的最大激活电流密度分别为(398.55±36.49)pA/pF、(238.62±30.78)pA/pF(n=10,P<0.01)和(354.08±35.16)pA/pF(n=10,P>0.05);激光作用可显著地影响瞬时外向钾通道电流的稳态激活和失活过程,对照组和激光照射组通道的半数激活电压分别为(-27.05±4.53) mV和(-2.10±3.14) mV(n=10, P<0.01),斜率因子分别为(-26.71±6.15) mV和(-20.70±4.38) mV(n=10,P<0.05),半数失活电压分别为(-70.49±7.21) mV和(-81.27±6.26) mV(n=10, P<0.01),斜率因子分别为(9.47±3.54) mV和(9.58±3.02) mV(n=10,P>0.05)。结果表明:弱激光作用海马神经元可以改变其瞬时外向钾通道特性,从而影响动作电位的形成和发放,调节神经元的生理功能,有利于受损神经元的恢复和再生。

Effects of low power laser irradiation on characteristics of transient outward potassium current of neurons

Based on the acutely isolated rat hippocampal CA3 pyramidal neurons irradiated by a semiconductor laser with wavelengh 670 nm and power 5 mW, the current characteristics of transient outward potassium channel were investigated using the whole-cell patch clamp technique. The experiments reveal that low power laser decreases the amplitudes of transient outward potassium current (I_A) in a voltage-dependent and reversible manner. The percentage of current inhibition is up to (40.13±5.19)% (n=10) depolarizing to +50 mV in laser irradiating 5 min. The maximal activation current densities of control group, irradiation group and recovery group are (398.55±36.49)pA/pF, (238.62±30.78)pA/pF (n=10, P<0.01) and (354.08±35.16)pA/pF (n=10, P>0.05), respectively. Laser irradiation markedly affect the activation and inactivation process of I_A. The half-activation voltage and the slope factor of the steady activation curve change under the laser's exposure. The former alters from (-27.05±4.53) mV to (-2.10±3.14) mV (n=10, P<0.01) and the latter from (-26.71±6.15) mV to (-20.70±4.38) mV (n=10, P<0.05). The half-inactivation voltage also changes from (-70.49±7.21) mV to (-81.27±6.26) mV (n=10, P<0.01) and the slope factor of the inactivation curves from 9.47±3.54 mV to 9.58±3.02 mV (n=10, P>0.05). The results indicate that the effect of low power laser on hippocampal neurons could change the current characteristics of transient outward potassium channel of membrane of neurons, and then affect the formation and firing of action potentials. Moreover, physiological function of neurons is adjusted as a result of low power laser irradiation, which might contribute to the restoration and regeneration of injured neurons.