RESUMO
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.