Editing Silent synapse (section)

== Characteristics ==
[[File:NMDA Receptor.png|thumb|368x368px|Membrane depolarization allows the NMDA receptor to respond to glutamate.]]
Silent synapses were proposed as an explanation for differences in [[quantal]] content of excitatory postsynaptic currents (EPSCs) mediated by AMPARs and NMDARs in [[hippocampal]] neurons.<ref name="Kullmann 1994">{{cite journal | vauthors = Kullmann DM | title = Amplitude fluctuations of dual-component EPSCs in hippocampal pyramidal cells: implications for long-term potentiation | journal = Neuron | volume = 12 | issue = 5 | pages = 1111–20 | date = May 1994 | pmid = 7910467 | doi = 10.1016/0896-6273(94)90318-2 | s2cid = 54357872 }}</ref> More direct evidence came from experiments where only a few axons were stimulated. 
The stimulation of a silent synapse does not elicit EPSCs when the postsynaptic cell is [[voltage clamp|clamped]] at -60 [[Volt|mV]]. Stimulation of a silent synapse ''will'' elicit EPSCs when the postsynaptic cell is depolarized beyond -40 mV.<ref name="Liao 1995">{{cite journal | vauthors = Liao D, Hessler NA, Malinow R | title = Activation of postsynaptically silent synapses during pairing-induced LTP in CA1 region of hippocampal slice | journal = Nature | volume = 375 | issue = 6530 | pages = 400–4 | date = June 1995 | pmid = 7760933 | doi = 10.1038/375400a0 | bibcode = 1995Natur.375..400L | s2cid = 4239468 }}</ref> This is because they lack surface AMPAR to pass current at hyperpolarized potentials, but do possess NMDARs that will pass current at more positive potentials (because of relief of magnesium block). Moreover, the EPSCs elicited with depolarized membrane potentials can be completely blocked by [[APV (NMDAR antagonist)|D-APV]], a selective NMDAR blocker.<ref name="Isaac 1995">{{cite journal | vauthors = Isaac JT, Nicoll RA, Malenka RC | title = Evidence for silent synapses: implications for the expression of LTP | journal = Neuron | volume = 15 | issue = 2 | pages = 427–34 | date = August 1995 | pmid = 7646894 | doi = 10.1016/0896-6273(95)90046-2 | doi-access = free }}</ref>