The speed at which the limited pool of synaptic vesicles can be replenished controls the rate of synaptic transmission. Collapse and slow retrieval of synaptic vesicles is involved in the mechanisms that operate at synapses in some neurons, but the details of these processes in the central nervous system have been unclear. Two papers in the June 5
Sunil P. Gandhi and Charles F. Stevens at The Salk Institute used an optical recording method to track individual synaptic vesicles, following a single electric shock. They observed that in living neurons from rat brains, exocytic events terminate via one of three vesicle retrieval methods: a fast, kiss-and-run mode that has a selective fusion pore, a slow, "compensatory" mode, and a "stranded" mode of recycling in which a vesicle is left on the...