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long term potentiation (LTP)

LTP is an activity-dependent synapse-specific increase in synaptic efficacy. It is long-lasting, persisting for days to weeks. LTP is a form of neuronal plasticity that may form the basis for associative learning. It has been demonstrated in 3 major excitatory pathways in the hippocampus: 1) the perforant pathway 2) mossy fiber pathway 3) Schaeffer collaterals LTP occurs when a brief high frequency train of stimuli is applied to any of the 3 pathways above. The result is an increase in excitatory postsynaptic potential which may last days to weeks. LTP has 3 important properties: 1) cooperativity (more than 1 fiber must be activated to facilitate LTP) 2) associativity* (Hebb's rule: LTP requires depolarization of the postsynaptic neuron coincident with activity of the presynaptic pathway) 3) specificity (LTP is specific to the active pathway) * LTP of the mossy fiber pathway may not be associative Ca+2 influx through NMDA receptors is critical for induction of LTP; it is also necessary for LTP decay [2]. Phosphorylation/dephosphorylation at GluR1 of AMPA receptors may also play a role. [3] In contast to LTD, high levels of intracellular Ca+2 are required for LTP. [3] The voltage-gated K+ channels, K+ A channel & K+ D channel may participate in LTP through inhibition or termination of Ca+ influx. [4]

Related

associative memory/learning (conditioning) hippocampal mossy fiber pathway learning NMDA receptor perforant pathway Schaeffer collaterals

General

facilitation (enhancement)

References

  1. Principles of Neural Science, 3rd ed., Kandel, Schwartz & Jessell (eds), Elsevier, NY, 1991, pg 1019-21
  2. Villarreal et al Nature neurosciences 5:48, 2001
  3. Castellani GC, Quinlan EM, Bersani F, Cooper LN, Shouval HZ. A model of bidirectional synaptic plasticity: From signaling network to channel conductance. Learn Mem. 2005 Jul 18; [Epub ahead of print] PMID: 16027175
  4. Takagi H et al, Time-sharing contributions of A- and D-type K channels in EPSP integration at a model dendrite Neurosci Lett 1998, 254:164 PMID: 10214983