Protein trafficking plays a central role in many aspects of neuronal functi
on, from the release of neurotransmitters by exocytosis and the recycling o
f synaptic vesicle proteins to the regulation of receptor signalling. Synap
tic function can be significantly modified on a short time scale by alterat
ions in the levels of receptors, ion channels and transporters both pre- an
d postsynaptically. In many cases, these alterations appear to be mediated
by acute changes in the rates at which the proteins are endocytosed from an
d exocytosed to the cell surface from intracellular pools. While our curren
t understanding of the signalling mechanisms and the intracellular pathways
responsible for these acute changes is still in its infancy: intriguing de
tails are beginning to emerge from a number of systems.