Mechanisms involved in hippocampal LTP: implications for retrograde messengers

Retrograde messengers have been implicated in the generation of synaptic plasticity in the hippocampus. In this article we summarise what is known about the mechanisms and loci of induction and expression of short-term and long-term potentiation to provide a platform for determining the necessity for, and properties of, a retrograde messenger. We describe the role of glutamate metabotropic receptors in the induction of short-term and long-term potentiation. We also present new data which question some of the arguments for a purely postsynaptic mechanism of expression of synaptic potentiation. We conclude that induction is postsynaptic while expression of short-term potentiation may be presynaptic and that there is probably the need for a fast acting retrograde messenger.