New sensors follow dopamine in the brain for more than a year

Dopamine, a signaling molecule used throughout the brain, plays a major role in regulating our mood and controlling movement. Many disorders, including Parkinson's disease, depression and schizophrenia, are linked to dopamine deficiency.

MIT neuroscientists have now devised a way to measure dopamine in the brain for more than a year, which they believe will help them learn more about its role in healthy and diseased brains.

"Despite all that is known about dopamine as an essential signaling molecule in the brain, involved in neurological and neuropsychiatric conditions as well as our learning ability, it has been impossible to track the changes in the report. to clinical conditions, "says Ann Graybiel, a professor at the MIT Institute, a member of the McGovern Institute for MIT Brain Research, and one of the lead authors of the study .

Michael Cima, Professor of Engineering David H. Koch at the Department of Materials Science and Engineering and member of the Koch Institute for Integrative Cancer Research at MIT and Rober Langer, Professor at the David H. Institute Koch and a member of the Koch Institute, are also the lead authors of the study. Helen Schwerdt, a postdoctoral fellow at MIT, is the lead author of the journal, which appears in the September 12 issue of Biology of communication.

Long-term detection

Dopamine is one of many neurotransmitters that brain neurons use to communicate with each other. Traditional dopamine measurement systems – carbon electrodes with a diameter of about 100 microns – can only be used reliably for about a day as they produce scar tissue that interferes with the ability of the electrodes to interact with dopamine.

In 2015, the MIT team demonstrated that tiny microfabricated sensors could be used to measure dopamine levels in a part of the brain called the striatum, which contains dopamine-producing cells essential for habit formation and Enhanced learning.

Because these probes are so small (about 10 microns in diameter), the researchers were able to implant up to 16 of them to measure dopamine levels in different parts of the striatum. In the new study, researchers wanted to test whether they could use these sensors for long-term monitoring of dopamine.

"Our fundamental goal from the start was to operate the sensors for a long time and produce accurate readings from one day to the next," Schwerdt says. "This is necessary if you want to understand how these signals are involved in specific diseases or conditions."

To develop a sensor that can be accurate over long periods, researchers had to make sure that it would not cause an immune response, to avoid scar tissue that interferes with read accuracy.

The MIT team found that their tiny sensors were virtually invisible to the immune system, even over long periods. After the implantation of the sensors, the populations of microglia (immune cells that react to short-term damage) and astrocytes, which react over longer periods, were the same as those of the brain tissues for which the probes n & ## They had not been inserted.

In this study, researchers implanted three to five sensors per animal, about 5 millimeters deep, into the striatum. They took readings every few weeks, after stimulating the release of dopamine from the brainstem, which goes to the striatum. They found that the measurements remained constant for 393 days.

"This is the first time anyone shows that these sensors work for more than a few months, which gives us great confidence that these types of sensors could be usable by humans." said Schwerdt.

Parkinson's disease surveillance

If they are developed for use in humans, these sensors could be useful for monitoring patients with Parkinson's disease who are receiving deep brain stimulation. This treatment involves implanting an electrode that delivers electrical impulses into a deep brain structure. Using a sensor to monitor dopamine levels could help doctors deliver stimulation more selectively, only when necessary.

Researchers are now looking to adapt sensors to measure other neurotransmitters in the brain and to measure electrical signals, which can also be disrupted in Parkinson's disease and other diseases.

"Understanding these relationships between chemical and electrical activity will be very important to understand all the problems you see in Parkinson's disease," said Schwerdt.

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