Editing Retrograde signaling (section)

====Mechanism====
The retrograde signaling hypothesis proposes that during the early stages of LTP expression, the postsynaptic cell "sends a message" to the presynaptic cell to notify it that an LTP-inducing stimulus has been received postsynaptically. The general hypothesis of retrograde signaling does not propose a precise mechanism by which this message is sent and received. One mechanism may be that the postsynaptic cell synthesizes and releases a retrograde messenger upon receipt of LTP-inducing stimulation.<ref name="Garthwaite 1991">{{cite journal | vauthors = Garthwaite J | title = Glutamate, nitric oxide and cell-cell signalling in the nervous system | journal = Trends in Neurosciences | volume = 14 | issue = 2 | pages = 60–7 | date = February 1991 | pmid = 1708538 | doi = 10.1016/0166-2236(91)90022-M | s2cid = 22628126 }}</ref><ref name="Lei 2000">{{cite journal | vauthors = Lei S, Jackson MF, Jia Z, Roder J, Bai D, Orser BA, MacDonald JF | title = Cyclic GMP-dependent feedback inhibition of AMPA receptors is independent of PKG | journal = Nature Neuroscience | volume = 3 | issue = 6 | pages = 559–65 | date = June 2000 | pmid = 10816311 | doi = 10.1038/75729 | s2cid = 21783160 }}</ref> Another is that it releases a preformed retrograde messenger upon such activation. Yet another mechanism is that synapse-spanning proteins may be altered by LTP-inducing stimuli in the postsynaptic cell, and that changes in conformation of these proteins propagates this information across the synapse and to the presynaptic cell.<ref name="Malenka 2004">{{cite journal | vauthors = Malenka RC, Bear MF | title = LTP and LTD: an embarrassment of riches | journal = Neuron | volume = 44 | issue = 1 | pages = 5–21 | date = September 2004 | pmid = 15450156 | doi = 10.1016/j.neuron.2004.09.012 | s2cid = 79844 | doi-access = free }}</ref>