Raastad M
Department of Neurophysiology, University of Oslo, Norway.
Eur J Neurosci. 1995 Sep 1;7(9):1882-8. doi: 10.1111/j.1460-9568.1995.tb00709.x.
The possibility of regular activation of unitary excitatory synapses on hippocampal CA1 cells by electrical stimulation of Schaffer collaterals was explored in the rat. The amplitude of the excitatory postsynaptic currents (EPSCs) and failures in response to a range of stimulation intensities around the threshold for the smallest detectable EPSC were analysed. After an abrupt appearance of EPSCs in response to increasing stimulation strength, both EPSC amplitude and failure rate could reach a plateau where increasing stimulation intensity did not cause additional responses. This was interpreted as a regular activation of mainly a single axon. Statistical methods showed, however, that only 12 out of approximately 50 experiments using threshold stimulation were without significant contamination from additional fibres. In this subset of experiments, upper limits for contamination from other fibres were estimated by using bootstrapping methods. More than 90% of the responses were probably due to faithful activation of a single axon, assuming that the density of axons connecting to one target cells is relatively homogeneous. This result makes the described method suitable for examining some aspects of the transmission between individual hippocampal cells.
在大鼠中探索了通过电刺激海马体CA1细胞的施万细胞侧支来定期激活单一兴奋性突触的可能性。分析了兴奋性突触后电流（EPSCs）的幅度以及对一系列围绕最小可检测EPSC阈值的刺激强度的反应失败情况。随着刺激强度增加，EPSCs突然出现后，EPSC幅度和失败率均可达到一个平台期，此时增加刺激强度不会引起额外反应。这被解释为主要是单个轴突的定期激活。然而，统计方法表明，在大约50次使用阈值刺激的实验中，只有12次没有受到其他纤维的显著污染。在这个实验子集中，通过使用自抽样方法估计了其他纤维污染的上限。假设连接到一个靶细胞的轴突密度相对均匀，超过90%的反应可能是由于单个轴突的可靠激活。这一结果使得所描述的方法适用于研究单个海马体细胞之间传递的某些方面。
