A unique experiment that helps to understand the mechanisms of depression, was conducted by specialists of Institute of Cytology and genetics, Siberian branch of the Russian Academy of Sciences. The staff of the laboratory of gene regulation within 30 days was observed for the mice that were forced to coexist with more aggressive individuals. Mice sitting in cages two by two: the animals were divided transparent barrier, and direct physical contact between them was no more than 5 minutes a day. Similar to the experience of chronic social stress in humans can be obtained, for example, in a situation where the chief daily intimidates a subordinate or the family with the aggravated internal conflict.
Researchers found that after 10 days of this coexistence in the more vulnerable experimental animals revealed signs of severe stress — in particular, they lose interest in communicating with other mice. However, the direct threat to life (such as a mouse dropped into a glass of water) rodents remain active and fiercely defended their lives. After 30 days, the mouse experience was much more passive: they were sedentary and eschewed even non-aggressive counterparts. And repeated the test “forced swimming” depressed individuals have not even tried to escape and limp back in the day.
— In acute stress animals are active, they are afraid the brain reacts to the external environment by changing its internal state. Depressing the mouse indifferent to the external stimuli, — explains senior researcher of the laboratory of regulation of gene expression, Natalia Bondar.
As scientists found out, the stress unlike depression affects a greater number of genes: over the 10-day experience temporarily changed the expression of 473 genes, but after the 30-day period there were only 35 “excited” of genes from different systems, and the rest returned to their previous state. However, prolonged stress causes the genes to stop responding to corticosterone, a stress hormone, helping to mobilize all forces of the body in case of danger, — because this is already in a state of depression, the animal becomes indifferent even to direct threats from the outside world. According to scientists, although mouse social model should be transferred to the human with caution, this experience helps to better understand the development of depression and in animals and in humans.
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