Scientists find brain pathway of depression in rats

The team, led by Karl Deisseroth, assistant professor of bioengineering and of psychiatry and behavioral sciences, found that in rats the differing mechanisms of depression and its treatment in the end appear to funnel through a single brain circuit. Changes in how the electrical signals spread through the circuit appear to be the cause of depression-related behavior, according to their study.

“I think this will help us make sense of how there can be so many different causes and treatments of depression,” said Dr Deisseroth. “It also helps us understand conceptually how something that seems as hard to get traction on as depression can have a really quantitative, concrete basis. You can use that common pathway as the most efficient, most direct targeted way to find truly specific treatments.”

The scientists developed a technique which allows intact brain circuits to be viewed in real time, enabling the researchers to watch living neurons in action, across entire brain networks. The system uses a fluorescent dye, sensitive to brain circuit activity, which the researchers introduce into the animal brain tissue.

As dyed circuits light up and darken again in response to electrical activity, very fast high-resolution cameras capture the action. The researchers can observe how different stimuli received by the animal, such as a dose of an antidepressant drug, affect circuit operation.

In the rats, they found an alteration in electrical activity flow through the brain that could be corrected by human antidepressants. The extent that the signal spread through the brain sample was diminished in the “depressed” rats. Dr Deisseroth predicted that, as noninvasive imaging of human brains gets better in the next few years, researchers will be able to measure these same quantitative measures in people as well. “That will be a wonderful thing when that happens,” he said.