Short, but short-lived stress is good for the brain
Stress improves memory
Stress, generally speaking, is a protective and adaptive reaction: if an animal gets into an unpleasant situation, stress hormones quickly mobilize the body's reserves so that it can cope with the troubles. In addition, the animal remembers the scheme of actions, and if it happens to get into the same situation again (for example, to wander into someone else's territory again and stumble upon the owner there), then the stress will not be so strong – because the understanding of how to act has remained from the last time.
It is clear that stress affects memory, since an individual can remember a stressful pattern of behavior. The main memory center in the mammalian brain is the hippocampus, and the researchers undertook to test how stress affects the neurons of this part of the brain. It turned out that stress neither more nor less stimulates neurogenesis, that is, the formation of new nerve cells.
In the diagram from the article in eLife, sections of the dorsal and ventral gyrus of the hippocampus are highlighted in red,
selected by the authors to assess the proliferation of nerve cells – VM.As is well known, stem cells that give rise to new neurons are preserved in the adult brain, and one of the places where these stem cells work is the dentate gyrus of the hippocampus.
As the researchers write in the journal eLife (Kirby et al., Acute stress enhances adult rat hippocampal neurogenesis and activation of newborn neurons via secret astrocytic FGF2, in the public domain), the dentate gyrus of the hippocampus is very sensitive to glucocorticoid stress hormones. However, so far all the experiments have said only that chronic stress, which is accompanied by an increase in stress hormones, suppresses the activity of nerve stem cells in the hippocampus. And therefore it also leads to memory deterioration, in addition to the standard set of "joys", such as obesity, depression and heart problems.
However, stress can be of various kinds: prolonged and not very strong, as well as short-term, but rather sharp (see the diagram from the press release of the University of California at Berkeley – VM).
Actually, the situation of a collision with an opponent-competitor is just the second kind. The experiments performed by Elizabeth Kirby and her colleagues simulated a short but severe stress. The rat was mechanically immobilized for several hours, while the level of stress hormones in her rose to the level characteristic of long-term stress, but the stress itself did not last long. As a result, scientists could observe how cells in the hippocampus of animals began to multiply intensively.
Moreover, two weeks after the stress, the animals began to perform better on memory tests. The researchers specifically labeled the "newborn" cells, and later it turned out that these cells were needed for the best performance of the task. At the same time, however, immediately after stress, there were no cognitive improvements in rats, apparently due to the fact that new cells need time to mature and integrate into neural networks.
The picture (authors – Daniela Kaufer and Liz Kirby) shows astrocytes (pink), in response to acute stress, enhancing the synthesis of fibroblast growth factor 2 (green), which stimulates the growth of new neurons (blue) – VM.
From a molecular and biochemical point of view, it was all about a signaling protein called fibroblast growth factor 2 (FGF2). After stress, the service cells of the nervous system, astrocytes, released a large amount of this protein, which spurred the formation of new neurons. Curiously, the tendency to depression is often correlated with a lack of this protein factor. Perhaps this is due to the fact that without FGF2, the brain does not have enough "workers", that is, neurons to cope with a difficult situation. In other words, stress can be not only harmful, but also useful: if you fall under the hot hand of the authorities, thanks to the new cells you can not only avoid a repetition of an unpleasant situation in the future, but also generally improve your memory and, accordingly, other cognitive abilities associated with it.
If the bosses are characterized by increased tyranny, the above advantages will be covered by the disadvantages associated with constant, incessant stress.
Prepared by UC Berkeley: Researchers find out why some stress is good for you.
Portal "Eternal youth" http://vechnayamolodost.ru17.04.2013