大鼠背根节神经元后超极化中Ca^(2+)激活K^+电流的蜂毒明肽敏感成分I_(AHP)

APAMIN SENSITIVE COMPONENT OF Ca^(2+)-ACTIVATED K^+ CURRENT OF AFTERHYPERPOLARIZATION,I_(AHP), IN DORSAL ROOT GANGLION NEURONS IN RAT

为了明确大鼠背根节（DRG）神经元中存在慢的Ca2+激活K+电流成分，本实验在新鲜分散的DRG神经元胞体上，采用全细胞电压箝技术，给予DRG神经元一定强度的去极化刺激，记录刺激结束后30ms时的尾电流幅度。结果发现：（1）随着去极化时间从1ms延长至180ms时，尾电流幅度由9．3±2．8pA逐渐增大至64.1±3．4pA（P＜0．001）；（2）当去极化结束后的复极化电位降低时，尾电流幅度先逐渐下降到零，然后改变方向，逆转电位约为-63mV；（3）细胞外施加500μmol／LCd2+或细胞内液中施加11mmol／LEGTA时尾电流明显减小甚至完全消失；（4）尾电流中慢成分的幅度在细胞外给与200nmol／L蜂毒明肽后，减小了约26.32±3。9％（P＜0。01）；（5）细胞外施加10mmol／LTEA，可明显降低尾电流中的快成分。结果提示，在DRG神经元启超极化中存在Ca2+激活K+电流的蜂毒明肽敏感成分──IAHP。

Whole-cell voltage clamp technique was used to record the tail current in freshly isolated dorsal root ganglion (DRG) neurons of rat with an aim to investigate whether these neurons possess an apamin sensitive component of Ca2+-activated K+ current,IAHP.The results are as follows: (1) the amplituds of the tail currents increased from 9.3 ±2. 8 pA to 64. 1 ± 3. 4 pA (P<0.001) when the depolarizing duration was increased from 1 ms to 180 ms; (2) the amplitudes 0f the tail current were reduced when repolarizing pulses were applied, with a reversal potential of about-63 mV; (3) the amplitude of the tail current was significantly depressed or even almost completely blocked by extracellularly applied 500 μmol/L Cd2+ or intracellularly applied 11 mmol/L EGTA;(4) the amplitudes of the tail currents were decreased by about (26. 32±3.9) % (P<0.01 ) after 200 nmmol/L apamin was extracellularly applied; and (5) the fast component of the tail current was sensitive to 10 mmol/L TEA while the slow component was insensitive. These results suggest that an apamin sensitive component of Ca2+-activated K+ current may be present in aftethyperpolarization of DRG neurons.