Journal of Neuroscience, Vol 8, 1645-1655, Copyright © 1988 by Society for Neuroscience
Mechanisms of long-term potentiation: a current-source density analysis
JS Taube and PA Schwartzkroin
Department of Physiology, University of Washington, Seattle 98195.
A current-source density (CSD) analysis was carried out in the CA 1 region
of the hippocampal slice (1) to determine the pattern of current flow in
pyramidal cells upon orthodromic stimulation and (2) to test the hypothesis
that EPSP-to-spike potentiation is produced by an alteration in this
distribution of current sinks and/or sources. The results indicated that 2
sinks occur near the cell body layer (in addition to the sink associated
with the EPSP) in response to orthodromic stimulation of the apical
dendrites. An early (i.e., short- latency) sink was present along the
radiatum/pyramidale border and was evident throughout the time course of
the evoked field potential. This sink peaked in magnitude just prior to the
peak of the population spike and was associated with orthodromic
stimulation; it was not seen with antidromic stimulation. A second, later,
sink occurred in the proximal portion of the basal dendrites and had a
characteristic time course similar to the population spike; this second
sink was also present during antidromic stimulation. There was some
suggestion that the earlier dendritic sink shifted apically with
development of long-term potentiation (LTP). The existence and movement of
such an active zone in these cells may help to explain the dissociation of
EPSP and spike potentiation in LTP.
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