LTP expression: hanging like a yo-yo?

Until a few years ago long-term potentiation or LTP was not a very popular subject for a cell biology-oriented audience. Recently, however, the picture has completely changed, mainly because most of the LTP papers are now dealing with specific molecules, second messengers, biochemical pathways, gene regulation, Ca2+ homeostasis, and so forth. This very big transition, has not led yet to a clear-cut picture on the actual locus of change after LTP induction and on the 'memory' molecule that bears the permanent change. Perhaps the biggest limitation is still the very small knowledge we have on how central synapses work. For this reason, at the moment, the most popular and conservative view is that LTP expression involves both pre- and postsynaptic changes. The aim of this review is to briefly summarize the status of LTP expression and to describe some possible future developments based on new approaches and techniques.