Researchers Find New Brain Mechanism Behind Depression


Neurons and neurotransmitters have been in the depression research spotlight for decades. Now, a different type of brain cell, the microglia, is getting some scientists’ attention.

About ten percent of the brain’s cells are microglia. They are there as part of our body’s immune system, ready to dispose of any infection that manages to cross the blood-brain barrier. Microglia also appear to be involved in depression pathology.

By discovering the involvement of microglia in depression development, researchers might have paved the way for new and possibly more effective medications for treating depressive symptoms.

Microglia, Mice, and Depression

Researchers at the Hebrew University of Jerusalem kept some mice in continuously stressful conditions for five weeks. The mice developed symptoms and behavior mirroring that of depressed people such as reduced social interaction, a decrease in pleasurable activity, and less neurogenesis or new brain cell generation.

The scientists discovered:

  1. Under duress, the mice microglia cells initially went through a phase of increased production and activity. After about a week, some microglia started to die.
  2. After five weeks of stress exposure, the microglia population was decreased and the remaining cells appeared to have degenerated—particularly in a brain area involved with stress response.
  3. Researchers could stop microglia degeneration, death, and the depressive mouse behavior during the study's early active phase by using genetic manipulation or drugs. These same treatments were not helpful to mice exposed to five weeks of constant stress.
  4. The mice that underwent 35 days of chronic stress did respond to microglia-stimulating drugs that restored the microglia population to normal levels. After a few days, the rodents enjoyed a complete recovery from their depressive symptoms and behavior.

“We were able to demonstrate that such microglia-stimulating drugs served as effective and fast-acting antidepressants...[and] our findings provide the first direct evidence that in addition to neurons, disturbances in the functioning of brain microglia cells have a role in causing psychopathology in general, depression in particular,” said researcher Professor Raz Yirmiya.

Source: Medical News Today


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