Brain Circuit Causes You to Feel Thirsty and Drink Water

What causes you to feel thirsty? It's your brain, of course. Now, scientists have identified a circuit in the brains of mice that regulates thirst, which tells them a bit more about this regulation in humans.

In this case, the researchers found the thirst-regulating circuit in a region of the brain called the subfornical organ (SFO). The SFO is a dedicated circuit that has two elements that likely interact with one another to maintain a balance so that you drink when you have to and you don't when you don't need to. This ensures that animals have the right amount of fluid to maintain blood pressure and other bodily functions.

In the past, when scientists had electrically stimulated various circumventricular organs in the brain of mice, including the SFO, they had received inconsistent results. That's why the researchers analyzed genetic markers, which allowed them to identify three distinct cell types in the SFO that were probably responsible for thirst.

In order to test whether the SFO was indeed responsible, the researchers introduced a light-sensitive protein into cells in the SFO. This allowed scientists to selectively activate the cells in the mice. The researchers then "switched on" the excitatory cells in the SFO that already had plenty to drink. When the cells were turned on, the mice began to avidly drink water for prolonged periods.

"It's very exciting," said Charles Zuker, one of the researchers, in a news release. "This circuit informs and directs the mouse into a complex program of actions and behaviors: 'I'm thirsty. I need to identify a source of water. I have to go where the water is. I have to begin to consume that water and I have to continue until the signal is suppressed.'"

The findings reveal a bit more about how our brains regulate behaviors. More specifically, it shows which parts of our brains are responsible, which could help scientists create better treatments for diseases in the future.

The findings are published in the journal Nature.

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