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A Biophysical Model of Bidirectional Synaptic Plasticity: Dependence on AMPA and NMDA Receptors
Gastone C. Castellani, Elizabeth M. Quinlan, Leon N Cooper and Harel Z. Shouval
Proceedings of the National Academy of Sciences of the United States of America
Vol. 98, No. 22 (Oct. 23, 2001), pp. 12772-12777
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3056981
Page Count: 6
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In many regions of the brain, including the mammalian cortex, the magnitude and direction of activity-dependent changes in synaptic strength depend on the frequency of presynaptic stimulation (synaptic plasticity), as well as the history of activity at those synapses (metaplasticity). We present a model of a molecular mechanism of bidirectional synaptic plasticity based on the observation that long-term synaptic potentiation (LTP) and long-term synaptic depression (LTD) correlate with the phosphorylation/dephosphorylation of sites on the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit protein GluR1. The primary assumption of the model, for which there is wide experimental support, is that postsynaptic calcium concentration and consequent activation of calcium-dependent protein kinases and phosphatases are the triggers for the induction of LTP/LTD. As calcium influx through the n-methyl-D-aspartate (NMDA) receptor plays a fundamental role in the induction of LTP/LTD, changes in the properties of NMDA receptor-mediated calcium influx will dramatically affect activity-dependent synaptic plasticity (metaplasticity). We demonstrate that experimentally observed metaplasticity can be accounted for by activity-dependent regulation of NMDA receptor subunit composition and function. Our model produces a frequency-dependent LTP/LTD curve with a sliding synaptic modification threshold similar to what has been proposed theoretically by Bienenstock, Cooper, and Munro and observed experimentally.
Proceedings of the National Academy of Sciences of the United States of America © 2001 National Academy of Sciences