Depression Brain Changes Explored
New discoveries are being made about changes in the brain during depression. Dr. Mia Lindskog of the Karolinska Institute, Sweden, and her team say that two separate mechanisms cause the emotional symptoms and the deficits in memory and learning seen in depression.
Dr. Lindskog explains that depression “is characterized by both emotional and cognitive symptoms.” However, she adds, “the relationship between these two symptoms of depression is poorly understood.”
The team compared ordinary rats against a strain of rats that had been bred with a disposition toward depression. This strain of rats has recently been found to have decreased emotional memory, impaired brain plasticity, and a smaller hippocampus.
The idea was to investigate the glutamatergic system, which is a system of amino acids vital for information processing in the hippocampus, in order to “reveal the mechanisms underlying the emotional and cognitive aspects associated with the disease.”
Clinical studies have shown abnormalities in the glutamatergic system in depressed people, but it is not yet clear how this affects the brain and contributes to depression symptoms.
All of the rats were injected with D-serine, a substance secreted by support cells for brain neurons called astrocytes. The “depressed” rats showed an improvement in their previously impaired brain plasticity and on memory tests.
Apathy was tested by releasing the rats into a container of water and observing whether they immediately tried to climb out or stayed floating in the container. The “depressed” rats showed no improvement in their level of apathy following the injection with D-serine.
“We have shown that there are two symptoms that can be influenced independently of one another, which means they could be treated in tandem in patients with depression,” said Dr. Lindskog. She added, “It’s likely that astrocytes perform a very important function in the brain.”