三七总皂苷对大鼠星状神经节后超极化电位的影响

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(ton ic)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ton ic细胞重复发放的频率下降。在0.12~0.16 g.L-1浓度范围内,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。

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

Aim To study the relationship between theeffects of saponins of panax notoginseng(PNS)on fir-ing frequency and hyperpolarization potential in neu-rons.Methods Applieation of a depolarizing currentpulse to stellate ganglion(SG) neurons of rat evokedaction potentials(AP).These neurons were classifiedas phasic or tonic neurons on the basis of their firingpatterns.Then we investigated the effects of PNS on fir-ing pattern and frequency,after hyperpolarization po-tential(AHP) and fastexcitatory postsynaptic potential(f-EPSP) in high Ca2 +Krebs’solution of SG neuronsin rat.Results The firing frequency of tonic neuronswas reduced by PNS.At the concentration of0.12 ~0.16 g.L-1,PNS reversibly depressed AHP in a dosedependentmanner.And the aggrandizing action of highCa2 +on f-EPSP was antagonized by PNS.Conclusion PNS can reduce the firing frequency of rat SG neu-rons,but this action was not caused by reinforcement ofAHP potential.The restraining regulation of excitabili-ty of neurons by PNS may underlie its inhibitory actionon calcium influx.