It turns out that the neurons of the brain are “to blame” for the excruciating feeling of hunger that makes us run to the refrigerator endlessly. It is they who prevent us from following a diet, scientists are sure.
Scientists at the Howard Hughes Medical Center have discovered what prevents us from refraining from snacking, for example, during a diet. The point is most likely in brain cells called AGRP neurons. Recent experiments have shown that they are responsible for the excruciating feeling of hunger.
In our time, when there is enough food around, such brain signals seem redundant, but from the point of view of evolution, they are justified. For ancient people and wild animals, foraging for food was often fraught with danger, and they needed motivation to take risks. “We believe that these cells are part of a very ancient system that motivates the body to satisfy its physiological needs. An animal or person is looking for food in part to silence those neurons, says team leader Scott Sternson. “And the brain cells that motivate us to search for food are also responsible for getting the pleasant sensations associated with it – when we are hungry, food seems to us tastier.”
Read more:
- How the brain makes us overeat
To understand how AGRP neurons work, the scientists conducted a series of experiments. In the first, well-fed mice were given two types of jelly – with strawberry and orange flavors. The mice tried both. The scientists then artificially activated AGRP neurons when the animals ate one of the types of jelly. The mice began to avoid him. In the next experiment, the researchers, on the contrary, turned off AGRP neurons when a hungry mouse ate one of the jelly. The rodents began to choose it – obviously, they “wanted” to turn off the unpleasant signals coming from the brain. In further experiments, it turned out that mice like to be in those places where they were turned off. AGRP neurons, and the animals tried to avoid places where they, on the contrary, were included.
Using a special microscope, the researchers studied the activity of AGRP neurons in the brains of hungry mice. As expected, these cells were active until the animals found food. Surprisingly, in order to “turn off” them, in fact, it was not required to eat – it was enough to see food or receive a signal associated with it. While the rodents were eating, cell activity remained low. In further experiments, Sternson’s group plans to figure out how to control the functions of AGRP neurons. Perhaps in the future this will help everyone who wants to follow a diet more successfully.
Подробнее см. J. Betley, S. Xu, Z. Cao, R. Gong, Ch. Magnus, Y. Yu, S. Sternson «Neurons for hunger and thirst transmit a negative-valence teaching signal», Nature, 2015.