Scientists show how the brain may be wired for drinking fluids

Scientists uncovered a high-resolution map of the wiring inside the mouse brain’s thirst center. With these blueprints, they could trick mice into becoming light or heavy water drinkers. Moreover, they discovered a quenching circuit that knew when to tell the brain, “Stop, the body has had enough.” Supported, in part, by the NIH’s Brain Research through Advancing Innovative Technologies (BRAIN) Initiative, the results may also provide a glimpse into the rules that govern how the brains circuits work.

“Bodily fluids are maintained by a delicate and tightly regulated balance of thirst and satiety. We genetically mapped out the neuronal circuits that tell the body when to drink,” said Yuki Oka, Ph.D., California Institute of Technology and senior author of the study published in Nature.

His group studied the circuits of the lamina terminalis, the thirst center located deep inside the brain. For decades, scientists knew that three groups of neurons in this area cooperated to control drinking, and they even had clues as to which type of neurons did so. But no one had a genetically defined circuit diagram for how they did it. Nor did they completely understand how the cells tell the body to stop drinking well before the stomach fully absorbs water and other fluids.

Using genes designed to help scientists dissect brain circuits, the researchers of this study found that opposing lines of communications running through an area of the lamina terminalis called the median preoptic nucleus (MnPO) may be critical players. One line was essentially responsible for telling the mice to drink while the other line told them when to stop. Both seemed to work in sequential order, relaying drinking or quenching messages from one neuron to another. Use of the mapping tools was supported by NIH’s BRAINInitiative.

“A goal of the BRAIN Initiative is to arm scientists with 21st century tools so they can fully understand how the healthy and diseased brain works at a level never seen before,” said Dr. Walter J. Koroshetz, M.D., director at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS). “This study is a good example how, after only a few years, the public’s investment in the BRAIN Initiative is paying off and helping researchers solve some of the mysteries of the brain.”