培养大鼠颈上神经节单烟碱受体通道及突触电流的膜片钳研究

NICOTINICSINGLE CHANNEL AND SYNAPTIC CURRENTS RECORDED FROM CULTURED RATSUPERIOR CERVICAL GANGLION NEURONS

在培养１─２周的大鼠颈上神经节交感神经元标本上，用膜片钳技术记录了单烟碱受体通道电流及胆碱能突触电流，并分析了它们之间的关系。单烟碱受体通道至少有三种亚导状态，即１５ｐＳ，２７ｐＳ，３８ｐＳ，其中以２７ｐＳ最常见。通道有两种开放模式，即单个短促开放与长串开放。对应的平均开放时间分别为τ＿１＝１．７１ｍｓ，τ＿２＝１２．２４ｍｓ。对自发突触电流的分析表明，其下降相的衰减时间常数（τ＝１５．７±１ｍｓ）与上述长串开放的持续时间相当，提示在突触传递过程中，突触前末梢释放的ＡＣｈ引起了突触后神经元烟碱受体通道的长串开放。

Nicotinic single channel and synaptic currents were recorded from cultured rat superiorcervical ganglion neurons to study how the kinetics of single channel openings determined themuIti-channel behavior.DM PP,a nicotinic agonist activated single channel events of at leastthree distinict conductance levels:15pS,27pS and 38pS,with 27pS beingthe most frequentlyseen conductance.The single channels generally had two gating modes,the single brief openingmode and the long burst opening mode,with mean open duration of 1.7 1 and 12.24ms,respectively.After 1-2 week in vitro,some neurons showed curare-blockable andTTX-resistant nicotinic miniature spontaneous synaptic currents(mSSCs).The mSSCs had amean decay time constant of 15.7± 1ms,which approximated more closely to the mean open du-ration of the long burst of openings.These data suggest that a single release of ACh frompresynaptic terminal produces a burst ofopenings of postsynaptic nicotinic channels.