三七总皂苷对大鼠星状神经节后超极化电位的影响

Effect of PNS on post hyperpolarization potential in rat stellate ganglion neurons

目的 研究三七总皂苷（PNS）对神经元放电频率的影响是否与改变膜电位的超极化程度有关：方法 向大鼠星状神经节（SG）细胞内输入去极化电流，诱发动作电位，区分相位式发放（phasic）细胞和紧张式发放（tonic）细胞，观察PNS灌流SG后，细胞放电类型和放电频率、后超极化电位（AHP）、高钙易化的快兴奋性突触后电位（f-EPSP）的变化。结果 PNS使tonic细胞重复发放的频率下降。在0．12～0．16g·L^-1沈度范围内，PNS对SG细胞的AHP有浓度依赖性抑制作用．PNS还能可逆性拮抗高钙对f-EPSP的易化作用。结论 PNS降低大鼠SG细胞的放电频率并非通过强化AHP电位引起，PNS对神经细胞兴奋性的抑制是因拮抗胞膜钙内流所致。

Aim To study the relationship between the effects of saponins of panax notoginseng （ PNS ） on firing frequency and hyperpolarization potential in neurons. Methods Application of a depolarizing current pulse to stellate ganglion （SG） neurons of rat evoked action potentials （AP）. These neurons were classified as phasic or tonic neurons on the basis of their firing patterns. Then we investigated the effects of PNS on firing pattern and frequency, after hyperpolarization potential （AHP） and fast excitatory, postsynaptic potential （f-EPSP） in high Ca^2＋ Krebs＇ solution of SG neurons in rat. Results The firing frequency of tonic neurons was reduced by PNS. At the concentration of 0. 12 -0. 16 g · L^-1, PNS reversibly depressed AHP in a dose dependent manner. And the aggrandizing action of high Ca^2＋ on f-EPSP was antagonized by PNS. Conclusion PNS can reduce the firing frequency of rat SG neurons, but this action was not caused by reinforcement of AHP potential. The restraining regulation of excitability of neurons by PNS may underlie its inhibitory action on calcium influx.