Distribution of synaptobrevin/VAMP 1 and 2 in rat brain.

The synaptobrevin/vesicle-associated membrane protein (VAMP) family of proteins, which are essential for neurotransmitter release, are the vesicle donor soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) proteins first described in synaptic vesicles at nerve terminals. Two synaptobrevin/VAMP isoforms are involved in calcium-dependent synaptic vesicle exocytosis, synaptobrevin/VAMP 1 and synaptobrevin/VAMP 2. However, the functional significance of these two highly homologous isoforms remains to be elucidated. Here, we used immunohistochemical, immunofluorescence and confocal microscope techniques to localize the two synaptobrevin/VAMP isoforms in rat brain areas, particularly in nerve terminals. Our results show that the two isoforms are present in the rat central nervous system and that their expression overlaps in some areas. However, a distinct distribution pattern was detected. Synaptobrevin/VAMP 2 is the most abundant isoform in the rat brain and is widely distributed. Although synaptobrevin/VAMP 1 is less abundant, it is the main isoform in particular brain areas (e.g. zona incerta at the subthalamus or nerve terminals surrounding thalamic neurons). The colocalization of synaptophysin with synaptobrevin/VAMP 1 demonstrates the presence of this isoform in subsets of nerve terminals. These results indicate that each synaptic vesicle donor SNARE protein isoform could have a specialized role in the neurosecretory process.