Synaptic vesicle pools.

Communication between cells reaches its highest degree of specialization at chemical synapses. Some synapses talk in a 'whisper'; others 'shout'. The 'louder' the synapse, the more synaptic vesicles are needed to maintain effective transmission, ranging from a few hundred (whisperers) to nearly a million (shouters). These vesicles reside in different 'pools', which have been given a bewildering array of names. In this review, we focus on five tissue preparations in which synaptic vesicle pools have been identified and thoroughly characterized. We argue that, in each preparation, each vesicle can be assigned to one of three distinct pools.