Long-term potentiation: Difference between revisions

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== Retrograde signaling ==

Retrograde signalling is a theoretical concept that arises from the question: "If LTP is induced postsynaptically, but expressed presynaptically, how does the presynaptic terminal "know" that LTP has been induced?" The obvious answer is that there must be some communication "backwards" across the synapse, that is, in the retrograde direction from the postsynaptic to the presynaptic side. This concept led to a flurry of work in the early 1990's to demonstrate the existance of a retrograde messenger and also to identify such a messenger. A number of candidates were examined including [[carbon monoxide]] (11331380){{ref|alkadhi-retro_co}}, [[platelet-activating factor]] (8906580)(8114914){{ref|kato-retro_paf}}{{ref|kato-retro_paf2}}, arachidonic acid, and nitric oxide (8978607)(9932440){{ref|arancio-retro_no}}{{ref|hawkins-retro_no}}.

Perhaps unfortunately for the retrograde signaling hypothesis, subsequent work has strongly established that LTP, at least early LTP, is expressed entirely postsynaptically (cf. Malenka and Bear, 2004). However, there is still life in the retrograde signalling hypothesis, since it has been demonstrated that ''induction'' of LTP may involve a retrograde messenger, since contrary to dogma, LTP induction does not appear to be entirely postsynaptic (Pavlidis, et al., 2000).