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J Neurosci. 2006 Aug 2;26(31):8183-94.

Nonlinear [Ca2+] signaling in dendrites and spines caused by activity-dependent depression of Ca2+ extrusion.

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  • 1Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.

Abstract

Spine Ca2+ triggers the induction of synaptic plasticity and other adaptive neuronal responses. The amplitude and time course of Ca2+ signals specify the activation of the signaling pathways that trigger different forms of plasticity such as long-term potentiation and depression. The shapes of Ca2+ signals are determined by the dynamics of Ca2+ sources, Ca2+ buffers, and Ca2+ extrusion mechanisms. Here we show in rat CA1 pyramidal neurons that plasma membrane Ca2+ pumps (PMCAs) and Na+/Ca2+ exchangers are the major Ca2+ extrusion pathways in spines and small dendrites. Surprisingly, we found that Ca2+ extrusion via PMCA and Na+/Ca2+ exchangers slows in an activity-dependent manner, mediated by intracellular Na+ and Ca2+ accumulations. This activity-dependent depression of Ca2+ extrusion is, in part, attributable to Ca2+-dependent inactivation of PMCAs. Ca2+ extrusion recovers from depression with a time constant of 0.5 s. Depression of Ca2+ extrusion provides a positive feedback loop, converting small differences in stimuli into large differences in Ca2+ concentration. Depression of Ca2+ extrusion produces Ca2+ concentration dynamics that depend on the history of neuronal activity and therefore likely modulates the induction of synaptic plasticity.

PMID:
16885232
[PubMed - indexed for MEDLINE]
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