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Sensitivity of synaptic plasticity to the Ca2+-permeability of NMDA-channels: a model of long term potentiation in hippocampal neurons.

E. De Schutter, J.M. Bower

Neural Computation 5:681-694 (1993)

Abstract - We have examined a model by Holmes and Levy (1990) of the induction of associative long term potentiation (LTP) by a rise in the free Ca2+ concentration ([Ca2+]) after synaptic activation of dendritic spines. The previously reported amplification of the change in [Ca2+] caused by coactivation of several synapses was found to be quite sensitive to changes in the permeability of the N-methyl-D-aspartate (NMDA) receptor channels to Ca2+. Varying this parameter indicates that maximum amplification is obtained at values that are close to Ca2+ permeabilities reported in the literature. However, amplification fails if permeability is reduced by more than 50%. We also found that the maximum free [Ca2+] reached in an individual spine during synaptic coactivation of several spines, depended on the location of that spine on the dendritic tree. Distal spines attained a higher [Ca2+] than proximal ones, with differences of up to 80%. The implications of this result for the uniformity of induction of associative LTP in spines in different regions of the dendrite are discussed.