Two studies have shed light on depression and anxiety by looking at what’s going on in the brains of mice.
The first study found a tiny group of neurons in the brains of mice that controls anxiety and depression. By manipulating them, researchers could turn emotional distress on and off.
Researchers already knew that anxiety starts in the amygdala. The team identified a small cluster of neurons in mice that, when overactive, spark anxiety, depression and social withdrawal. When the neurons are calmed down, the symptoms stop almost completely.
“We already knew the amygdala was involved in anxiety and fear, but now we’ve identified a specific population of neurons whose imbalanced activity alone is sufficient to trigger pathological behaviors,” said the team’s leader, neuroscientist Juan Lerma at Spain’s Institute for Neurosciences.
The researchers manipulated a gene that excites neurons. Mice that were bred to overexpress the gene were nervous, avoided making friends or going into open areas and were generally withdrawn from social activities. When the researchers used genetic tools to fix the gene, the mice behaved in healthy ways.
The team used the same genetic tools on mice that were naturally anxious and withdrawn, not ones that were specifically bred for it. Those mice also had lower anxiety after treatment and interacted with new mice more readily, showing less social anxiety.
But memory problems are often associated with depression. The mice that were struggling with anxiety still struggled with object recognition after treatment. That suggests the memory problems linked to mental health concerns may be located in another part of the brain.
A second study, from the Univ. of Utah, found another potential route to treating anxiety through research in mice’s brains. Their research found that immune cells in the brain called microglia impact anxiety. One kind of microglia can spur anxiety while another can quell it.
“This is a paradigm shift,” said Dr. Donn Van Deren. “It shows that when the brain’s immune system has a defect and is not healthy, it can result in very specific neuropsychiatric disorders.”
For their study, the researchers used mice that didn’t have any microglia in their brains and transplanted the cells into them. The mice who received the anxiety-provoking cells groomed themselves compulsively and didn’t like open spaces. The ones who received the anxiety-suppressing microglia weren’t anxious. And mice who got both types weren’t anxious either. That showed balance might be the key to mental health.
Humans also have two kinds of microglia that act in the same role. But no current medications focus on the microglia. The team thinks medications that treat microglia imbalances could be a way forward.
These studies had very different findings. It’s important to recognize that they were in mice, not humans. But it does show the importance of having researchers look at problems from several angles. Both of these studies may offer new ways to treat mental health that could benefit different people.
