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To sustain neurotransmission, synaptic vesicles and their associated proteins must be recycled locally at synapses. Synaptic vesicles are thought to be regenerated approximately 20 s after fusion by the assembly of clathrin scaffolds or in approximately 1 s by the reversal of fusion pores via 'kiss-and-run' endocytosis. Here we use optogenetics to stimulate cultured hippocampal neurons with a single stimulus, rapidly freeze them after fixed intervals and examine the ultrastructure using electron microscopy--'flash-and-freeze' electron microscopy. Docked vesicles fuse and collapse into the membrane within 30 ms of the stimulus. Compensatory endocytosis occurs within 50 to 100 ms at sites flanking the active zone. Invagination is blocked by inhibition of actin polymerization, and scission is blocked by inhibiting dynamin. Because intact synaptic vesicles are not recovered, this form of recycling is not compatible with kiss-and-run endocytosis; moreover, it is 200-fold faster thanclathrin-mediated endocytosis. It is likely that 'ultrafast endocytosis' is specialized to restore the surface area of the membrane rapidly., Recycling of synaptic vesicle membrane and proteins is required to keep membrane surface area constant and ensure efficient neurotransmission during sustained synaptic activity. Classical ultrastructural analysis of frog neuromuscular junctions [...]

Author(s): Jean-Louis Bessereau [1]; Ashley Wright; Daniel C. Williams; Kim Schuske; M. Wayne Davis; Erik M. Jorgensen (corresponding author) Transposons have been enormously useful for genetic analysis in both Drosophila [...]

Author(s): Janet E. Richmond [1]; Robby M. Weimer [1]; Erik M. Jorgensen (corresponding author) The priming step of synaptic vesicle exocytosis is thought to require the formation of the SNARE [...]

The gene unc-47 has been implicated in the release of gamma-aminobutryic acid (GABA), in studies of the nematode Caenorhabditis elegans. Further research shows that the sequence of unc-47 predicts a 10 transmembrane domain protein, the gene is expressed by GABA neurons and that the protein colocalizes with synaptic vesicles. This vesicular GABA transport (VGAT) is compared with a vesicular transporter for monoamines, and indicates differences in bioenergetic transport dependence.

The synaptotagmin mutants of the nematode Caenorhabditis elegans has almost no synaptic vesicles at the synaptic terminals. The absence of synaptotagmin impairs both endocytosis and exocytosis which are involved in the recycling of synaptic vescicles. Therefore, synaptotagmin participates both in exocytosis and endocytosis of synaptic vesicles. Defective accumulation of synaptic vesicles from the plasma membrane or defective vesicular recycling causes such reduction.

Gamma-aminobutyric acid (GABA) can excite as well as inhibit postsynaptic membranes. It is the most abundant inhibitory neurotransmitter, and its receptors are the target of many drugs and insecticides. The functions of 25 of the 26 GABAergic neurons in the nematode Caenorhabditis elegans were analyzed as to how they control the body and enteric muscles to produce different behaviors.

The nematode Caenorhabditis elegans requires five genes for proper gamma-aminobutyric acid (GABA) function. These five are unc-25, unc-30, unc-46 unc-47 and unc-49. Each seems responsible for a number of functions, and some appear to encode familiar chemicals. Unc-30 is required for some neural differentiation; unc-25, unc-47 and unc-47 for presynaptic GABAergic function with the latter two influencing the release of GABA into the synaptic cleft; and unc-49 for postsynaptic function.