Run after high

No one knows why the squirrel is spinning in the wheel. But with the mice, the situation cleared up: according to the study of German scientists under the leadership of Peter Gass from the University of Heidelberg [1], a five -hour run causes the euphoria of the runner due to the same physiological mechanism that explains the effect of marijuana.

The term "euphoria of the runner" appeared in the USA in the 1970s in the wake of the passage of a coward with a run, but the indicated state of emotional and physical upsurge can be associated with any prolonged physical exertion. Almost always, this condition is accompanied by a decrease in pain, a decrease in anxiety and a sense of general peace. People who have experienced the euphoria of the runner in a particularly vivid form, note unexpected sensations: a slowdown in time, extraordinary ease and loss of conscious control over the body. All this is wonderful, but how can you study euphoria in mice?

Most of the listed signs are subjective, but three of them can be found using behavioral tests. For example, this: the mouse is planted in a two -room box, where one compartment is brightly lit, and the other is not lit at all, and measure how much time the animal will spend in each of them. Any mouse will consider the dark compartment to be safer, but from time to time it will also be explored by illuminated too. The stronger the mouse is alarmed, the less often it will come out and the more time it will spend on the dark side - this is a test for anxiety. In another test - on sensitivity to pain - the mouse is put on a hot platform and cut it out before it begins to lick your paws or bounces. The third sign - a general sedative effect, or peace - measure to reduce physical activity.

In the study under discussion, a group of 16 mice, which had previously run in a wheel in 5 hours an average of 6.5 km, showed a significant decrease in anxiety and sensitivity to pain compared to a control group, deprived of the same 5 hours to run. After testing, all mice for an hour received at their disposal on the wheel - here the running animals behaved calmer and ran fewer animals from the control group, which indicates a sedative effect of a five -hour run. Having thus proved the presence of an euphoria of the runner in mice, the researchers began to clarify the mechanism of its occurrence.

For a long time it was believed that the euphoria of the runner was caused by endorphins - the natural analogues of opioids. It was shown that both the mouse and in humans, the concentration of endorphins in blood plasma increases after the run. However, later it turned out that the beta-endorphin could not pass through the hematoencephalic barrier to the brain, and when the antagonists of the endorphins are introduced, the sensation of euphoria in the athletes does not disappear. Then other substances were discovered, the concentration of which in the blood correlates with physical activity - endocannabinoids. These are patient compounds similar to the active substances of hash and marijuana. It was shown that blocking in mice of the receptors of these connections leads to a decrease in the average distance running in the wheel.

To find out whether endorphins and endochanabinoids are associated with the studied features, in this work the mice also introduced blockers of different receptors and checked how this would affect the passage of tests. It turned out that blocking the receptors associated with endorphins does not affect the manifestations of signs of euphoria - a decrease in anxiety and pain sensitivity, as well as the general peace after the run, does not depend on endorphins. However, the appeal does not depend on endocannabinoids too - well, the authors say, perhaps, a decrease in physical activity after five hours in the wheel is due to fatigue than with euphoria.

For the remaining two signs, the normal functioning of endocannabinoid receptors was critical. The effect of pain relief disappears when any endocannabinoid receptors are blocked, and the effect of reducing anxiety is only when blocking endocannabinoid receptors of CB1 located in the central nervous system. To confirm the significance of these receptors for the emergence of the euphoria of the runner, a special line of mice was taken, which did not have CB1 receptors on the surface of GABA-ergic neurons. Indeed, such mice does not find the signs of euphoria under consideration. Only fatigue is found, which the authors persistently call the sedative effect.

1. J. Fuss et al . A runner ' S High Depends on Cannabinoid in Mice. ProC . Natl . ACAD . SCI USA , 2015. 112 (42): 13105-3108 .