Decipher the mystery of thirst: Why does it form and why does it disappear?

Try answering a question, before you continue reading this article: 'Are you thirsty?'.

It may sound silly, but most people will not have an immediate answer. Because so far, thirst is something that naturally comes to you first. And you, you never naturally go to seek thirst, to ask if I should drink water or not?

In fact, the thirst has always been a mystery of science: Why does it form and why does it disappear?

Until now, thirst is something that naturally comes to you first.

When you think about thirst, everything seems simple: Go find water, drink and return to what you are doing. Thirst is like a naughty kid and annoys you, but just need 1 cup of water, like putting a child in a crib, you can dispel it.

But in fact, there's something quite profound going on when you drink water to satisfy your thirst. Starting with dehydration, your blood is thicker and nerve cells in your brain send out a signal, release the child, and tell you you need to drink water.

Then, once you drink water, almost immediately you feel satisfied. It conflicts with the initial mechanism of thirst, because you don't pour water directly into your blood. It will take at least 10 - 15 minutes, maybe longer, for water from the stomach to enter the blood. So how does the brain know that you are thirsty?

It seems obvious, but for some people with polysipsia syndrome , their brains really don't know when they are thirsty. As a result, these people often drink too much water, causing blood to dilute. Even this can be life-threatening, when drinking too much water lowers blood sodium - a fatal victim confirmed to be poisoned with water.

When neuroscientists at the California Institute of Technology (Caltech) think about: ' How and why are we thirsty?', They have shed light on a small corner of the problem. In the process of understanding how the brain monitors and monitors the body for drinking water, they have identified a set of neurons that receive signals, when mice are thirsty for drinking water.

Emerging in the center of the brain's thirst for control, these signals seem to be the one responsible for the quick satisfaction that comes from drinking water. It not only conveys the information of the water being drunk, but also measures how much water is flowing, the mice are drinking little by little or cultivating big sips.

If these signal circuits work in the same way on humans, it may be the key to understanding neuroscience about what happens when we are thirsty.

Neurons (red) in the brain respond to thirst.

In the last few years, biologists have been able to map the neuron map, in an area in the brain that controls thirst, according to Professor Yuki Oka at Caltech. It has been observed that neurons in this area turn off after the mice were given water. But the reason why is still a mystery.

A graduate student in Dr. Oka's laboratory, Vineet Augustine, has conducted a series of experiments with genetically modified mice, to keep track of the connections between these neurons more easily. In Augustine's experiments, when a neuron causes a mutation of another neuron, it is re-labeled. The result, is a long trail of interconnected neurons found.

This trail extends to its starting point, which is the neurons in an area called median preoptic nucleus . It turns out that the neurons here have 'told' neurons in the thirst control area that water is being drunk when that happens.

Subsequent experiments showed that mice disabled with these neurons drank twice as much water as normal. In the opposite case, when cells are actively activated without thirst, the mice did not drink even if they were dehydrated.

The most interesting thing is that these nerve cells do not react to the water itself, Augustine said. Researchers found that when a mouse drank water with a large flux, similar to the fact that you are in a rush, these neurons will work.

But when the water was dripped slowly, although the same amount of water remained, the mouse did not respond to the thirst. The same thing happens when it chews on water-containing gel particles.

Conversely, when the mice drink oil and not water, their neurons are activated."That just tells us it is possible that the speed - the speed of the swallowing reaction - is what these neurons are responding to ," Augustine said.

Clearly, the fast swallowing response is a good sign for the brain to know a person is drinking water. In natural conditions, it is reliable enough for instant brain satisfaction, when it feels how much water swallowing is enough.

This instant gratification mechanism has an important role. According to Dr. Oka speculation, naturally taught animals to drink water in the minimum time. Because when an animal drinks water, it will be distracting and vulnerable. For example, a deer easily attacked when it bent down to the river to drink water, the posture of bending down also made it dangerous.

Therefore, it is best to swallow water as quickly as possible."If you double the swallowing time, the risk of eating meat will double," Dr. Oka said.

The posture of drinking natural water is not conducive to alerting hazards.

Thus, the logical answer to the question 'Why can you satisfy your thirst immediately and how the brain correctly measures the amount of water it needs?' was:

"The reaction of a chain of neurons originates from the central prefrontal nucleus, which responds to a series of rapid swallowing in the mouth and throat. It may come from the instinct of animals, to drink water quickly and satisfactorily. satisfy the thirst for immediate relief with the surrounding world, full of predators and other dangers ".

Also, is there anything involved in this strange process? That's what scientists are continuing to learn. For example, Augustine's group is looking into whether our intestines have a 'sensor' that can measure water and alert the brain.

Research by Dr. Oka and Augustine was published in Nature magazine.