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The Journal of Neuroscience, 2001, 21:RC170:1-6
RAPID COMMUNICATION
Postsynaptic Depolarization Scales Quantal Amplitude in Cortical
Pyramidal Neurons
Kenneth R.
Leslie,
Sacha B.
Nelson, and
Gina G.
Turrigiano
Department of Biology and Center for Complex Systems, Brandeis
University, Waltham, Massachusetts 02454
Pyramidal neurons scale the strength of all of their excitatory
synapses up or down in response to long-term changes in activity, and
in the direction needed to stabilize firing rates. This form of
homeostatic plasticity is likely to play an important role in
stabilizing firing rates during learning and developmental plasticity,
but the signals that translate a change in activity into global changes
in synaptic strength are poorly understood. Some but not all of the
effects of long-lasting changes in activity on synaptic strengths can
be accounted for by activity-dependent release of the neurotrophin
brain-derived neurotrophic factor (BDNF). Other candidate activity
signals include changes in glutamate receptor (GluR) activation,
changes in firing rate, or changes in the average level of postsynaptic
depolarization. Here we combined elevated KCl (3-12 mM)
with ionotropic receptor blockade to dissociate postsynaptic
depolarization from receptor activation. Chronic (48 hr)
depolarization, ranging between 62 and 36 mV, parametrically reduced the quantal amplitude of excitatory synapses in a
BDNF-independent manner. This effect of depolarization did not depend
on AMPA, NMDA, or GABAA receptor signaling,
action-potential generation, or metabotropic GluR activation.
Together with previous work, these data suggest that there are two
independent signals that regulate activity-dependent synaptic scaling
in pyramidal neurons: low levels of BDNF cause excitatory synapses to
scale up in strength, whereas depolarization causes excitatory synapses
to scale down in strength.
Key words:
BDNF; synaptic scaling; activity-dependent; synaptic
plasticity; KCl; depolarization; mEPSC
Copyright © Society for Neuroscience 0270-6474//$05.00/0
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