In Brief
A team of scientists at Stanford has identified the exact neurons responsible for controlling thirst. They made this remarkable discovery by using light to activate and deactivate individual neurons within the brains of mice.

A Thirst for Knowledge

More than 60 years ago, researchers first identified the part of the brain that controls the feeling of thirst. Now, a team of scientists has identified the exact neurons responsible for telling our bodies when we need to reach for a beverage.

Led by Stanford neuroscience researcher William E. Allen, the team made this discovery by first depriving mice of water for 48 hours. Then, they analyzed the RNA expression in the animals’ median preoptic nucleus (MnPO), the area of the brain previously linked to thirst. Through this analysis, the researchers were able to narrow down their area of interest to specific clusters of neurons within a particular region of the brain.

Next, the researchers focused on how manipulating these neurons would affect water consumption in the mice. When they inhibited the activation of the neurons via optogenetics (the use of light to control genetically modified cells) they noticed that the mice decreased their water consumption. Conversely, when the neurons were activated, water consumption increased.

Some of the mice in the study were trained to access water by pressing a lever. The researchers noticed that when the neural activity in these mice decreased — a sign they weren’t thirsty — so did the rate at which they pressed the lever.

Meanwhile, when mice were given the opportunity to stop the photoactivation of their MnPO neurons by pressing the lever, they did so “vigorously” — expressing a strong desire to free themselves from their feeling of unquenchable thirst.

The Next Level of Humanity

Thirst is one of our most basic drives. If we don’t ingest the appropriate amount of water, our bodies can become dehydrated, causing our biological systems to shut down. Ultimately, we can die of thirst. Conversely, too much water can be problematic as well, causing the cells in our bodies to swell and potentially leading to seizures, coma, and death.

This new research from Stanford could lead to treatments that help people suffering from conditions such as adipsia (a lack of thirst) and polydipsia (an unquenchable thirst) make up for their bodies’ inability to naturally maintain appropriate hydration levels.

Even more broadly, this research tells us something about the brain that we didn’t previously know. Despite the vast amount of research in the field of neuroscience, the brain is still largely a mystery, and each new discovery puts us one step closer to unlocking its secrets.

Not only could a more complete understanding of the brain lead us to better treatments for psychological and neurological disorders, it could also help us reach the next level in human evolution — a time when we navigate virtual reality (VR) through thought alone, control bionic devices with our minds, and access the digital world via brain implants.