Warren D, Lavidis N A, Bennett M R
Department of Physiology, University of Sydney, N.S.W., Australia.
J Auton Nerv Syst. 1996 Jan 5;56(3):175-83. doi: 10.1016/0165-1838(95)00087-9.
Synaptic transmission from single preganglionic hypogastric nerves innervating monopolar pelvic ganglion neurones has been studied with intracellular electrodes to record transmission from all the boutons and with extracellular electrodes placed over boutons visualized with DiOC2(5) in order to record transmission from selected boutons. Intracellular electrodes revealed spontaneous excitatory postsynaptic potentials (EPSPs) with amplitude histograms that show increasing numbers of large EPSPs as the external calcium ([Ca2+]o) was increased from 0.15 to 1.0 mM. These histograms were in general well fitted by a Poisson mixture of gamma distributions. Extracellular electrodes placed over visualized boutons revealed evoked excitatory postsynaptic potentials (extracellular EPSPs) with amplitude histograms that were best described by single gamma distributions in most cases in low [Ca2+]o (less than 0.5 mM). The standard deviation of these gammas was not much larger than that of the electrical noise. In a minority of extracellular recordings the amplitude histogram of evoked extracellular EPSPs was best described by a gamma distribution in which the standard deviation was much greater than that of the noise. Confocal microscopy of boutons orthogradely labelled with dextran-rhodamine showed that about 30% of these formed closely apposing pairs on the surface of the neurones. These observations are discussed in terms of the hypothesis that multiquantal release at boutons occurs as a consequence of the coupled secretion from closely apposed boutons.
利用细胞内电极记录来自所有终扣的传递，以及将细胞外电极置于用DiOC2(5)可视化的终扣上，以记录来自选定终扣的传递，对支配单极盆腔神经节神经元的单个节前腹下神经的突触传递进行了研究。细胞内电极记录到自发兴奋性突触后电位（EPSP），其幅度直方图显示，随着细胞外钙浓度（[Ca2+]o）从0.15 mM增加到1.0 mM，大EPSP的数量增多。这些直方图总体上能很好地用伽马分布的泊松混合模型拟合。置于可视化终扣上的细胞外电极记录到诱发兴奋性突触后电位（细胞外EPSP），在低[Ca2+]o（小于0.5 mM）的大多数情况下，其幅度直方图最好用单伽马分布来描述。这些伽马分布的标准差并不比电噪声的标准差大很多。在少数细胞外记录中，诱发的细胞外EPSP的幅度直方图最好用标准差远大于噪声标准差的伽马分布来描述。用葡聚糖罗丹明正向标记终扣的共聚焦显微镜显示，其中约30%在神经元表面形成紧密相邻的配对。根据紧密相邻终扣耦合分泌导致终扣多量子释放的假说，对这些观察结果进行了讨论。
