Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 52, Pages 19121-19125Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0509856103
Keywords
spike-timing-dependent plasticity; NMDA receptors; nifedipine; calcium imaging; entorhinal cortex
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Funding
- NINDS NIH HHS [NS34425, R01 NS034425, R56 NS034425, R29 NS034425] Funding Source: Medline
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Repeated induction of pre- and postsynaptic action potentials (APs) at a fixed time difference leads to long-term potentiation (LTP) or long-term depression (LTD) of the synapse, depending on the temporal order of pre- and postsynaptic activity. This phenomenon of spike-timing-dependent plasticity (STDP) is believed to arise by nonlinear processes that lead to larger calcium transients (and thus LTP) when presynaptic APs precede postsynaptic APs and smaller calcium transients (and thus LTD) when postsynaptic APs precede presynaptic APs. In contrast to predictions from such calcium-peak-detector models, we show that constitutively or artificially broadened APs in layer II/III pyramidal cells of entorhinal cortex (EC) lead to an increase in the dendritic calcium transient and shift the balance of STDP toward LTD. STDP in entorhinal pyramidal cells is NMDA-receptor-dependent and modulated by the Ca(V)1 Ca2+ channel-blocker nifedipine. Results are consistent with an elaboration of the calcium-peak-detector model in which downstream signals from voltage-dependent Ca2+ channels suppress LTP relative to LTD. Our results suggest that modulation of AP width is a potent way to adjust the rules of synaptic plasticity in the EC.
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