Triggering thirst with the flip of a switch

Thirsty? Craving a large glass of cold, refreshing water?

Now, what if you could trick your brain into thinking you weren’t thirsty in the first place without ingesting a single drop, or make yourself believe you are thirsty when you are not?

In a study published Monday in the journal Nature, scientists at Columbia University revealed the on/off switches for regulating thirst in the brains of mice. The scientists isolated two sets of neurons in the brain’s subfornical organ (SFO) — CAMK11, which signals thirst, and VGAT, that erases it — and were able to trigger both.

The researchers tested the triggers by first placing a light-sensitive protein into the cells of the mice, which allowed them to shine specific lights onto the mice in order to trigger the neurons. When scientists turned on a light activating the CAMK11 neurons, they found that mice that were well-hydrated as well as mice that were dehydrated both drank water continuously until the light was switched off. When the VGAT neurons were activated, the opposite happened: mice stopped drinking water, even if they were dehydrated.

Whether thirst was activated or deactivated in the mice, the scientists also found that the animals’ interests in salt or food were not affected, meaning that the neurons were responsible for water intake alone.

“The SFO is one of few neurological structures that is not blocked by the blood-brain barrier — it’s completely exposed to the general circulation,” said Dr. Yuki Oka, lead author of the paper. “This raises the possibility that it may be possible to develop drugs for conditions related to thirst.”