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Extracellular Activation of Unitary Excitatory Synapses Between Hippocampal CA3 and CA1 Pyramidal Cells
Author(s) -
Raastad Morten
Publication year - 1995
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.1995.tb00709.x
Subject(s) - hippocampal formation , excitatory postsynaptic potential , neuroscience , extracellular , hippocampus , chemistry , pyramidal cell , biology , inhibitory postsynaptic potential , biochemistry
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 ∼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 cell is relatively homogeneous. This result makes the described method suitable for examining some aspects of the transmission between individual hippocampal cells.