<< (..) researchers were able for the first time to view the release and re-uptake of dopamine — a neurotransmitter involved in motor learning, habit formation, and reward-seeking behavior — in individual synapses. When all the neurons were electrically stimulated in a sample of brain tissue, the researchers expected all the synapses to release dopamine. Instead, they found that less than 20 percent of dopaminergic synapses were active following a pulse of electricity. >>
The case of the silent synapses: Why are only 20% of synapses active during neurotransmission? Unknown information coding in the brain? February 26, 2016
http://www.kurzweilai.net/study-finds-only-a-small-portion-of-synapses-may-be-active-during-neurotransmission
Daniela B Pereira, Yvonne Schmitz, et al. Fluorescent false neurotransmitter reveals functionally silent dopamine vesicle clusters in the striatum. Nature Neuroscience (2016) doi:10.1038/nn.4252. Published online 22 February 2016
http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.4252.html