Need a Drink?

After taking your dog for a run on a warm sunny day, it’s likely that your first instinct upon returning home is to gulp down a whole glass of water. Fido slurps from his bowl, too, as you’re both driven to the same specific behavior by a signal that the body’s healthy ratio of salt to water is getting out of balance. But how does that signal result in the desire to drink water? Assistant Professor of Biology Yuki Oka has pinpointed specific neurons in the brain that control this response, at least for mice. Oka and his colleagues focused a recent study on the circumventricular organs—the regions related to the hypothalamus that were previously suggested to play a role in thirst. Using optogenetics, a technique that allows the control of neural activities with light, the researchers found two distinct populations that controlled the animal’s water-drinking behavior. When the researchers “turned on” the first group of neurons, it evoked an intense drinking behavior even in fully water-satiated mice. The activation of a second group of neurons, on the other hand, could block the desire to drink even in highly water-deprived animals.

Although the work was done in mice, Oka says the finding suggests that there are innate brain circuits that can act as “switches,” creating or erasing the desire to drink water—and that these circuits could act as a thirst control center in humans, too.

--Written by Jessica Stoller-Conrad

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