Scientists have developed a new optical technique to study how information is transmitted in the brains of mice. Using this method, they found that only a small portion of synapses — the connections between cells that control brain activity — may be active at any given time.
The study was published in the latest issue of Nature Neuroscience.
To obtain a detailed view of synaptic activity, the researchers developed a novel compound called fluorescent false neurotransmitter 200 (FFN200). When added to brain tissue or nerve cells from mice, FFN200 mimics the brain’s natural neurotransmitters and allows researchers to spy on chemical messaging in action.
Using a fluorescence microscope, the researchers were able to view the release and reuptake 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.
“This particular study didn’t explain what’s causing most of the synapses to remain silent,” said David Sulzer, a co-author of the paper. “If we can work this out, we may learn a lot more about how alterations in dopamine levels are involved in brain disorders such as Parkinson’s disease, addiction, and schizophrenia.”
Source: Columbia University Medical Center