Charles Zuker and colleagues from Howard Hughes Medical Institute are the first to absolutely identify two types of cells that form a circuit that controls how much water that an animal drinks. This is the first known discovery of a brain mechanism that controls how much water an animal needs to consume.
The researchers found two different types of cells that are involved in regulating how much water an animal consumes. Both types of cells are located in the region of the brain called the subfornical organ. This region of the brain comes into direct contact with body fluids. The contact with body fluids allows the two types of cells to determine the need for water based on the electrolyte composition of body fluids.
The two cells form a circuit that ensures animals take in the right amount of water to maintain blood pressure, electrolyte balance, and cell volume. The researchers saw different levels of activity in the subfornical organ when test mice were dehydrated and when the mice had enough water. The activity of both types of cells was found to be independent of water concentration.
The researchers added a light controlled gene to each type of cell. The cells could be made to react by light. One type of cell caused the test mice to drink as much as eight percent of their body weight in water. The second type of cell caused the test mice to reduce their consumption of water by as much as 80 percent as long as the light that stimulated the cell remained on. Together the two types of cells form a feedback circuit that maintains the amount of water in an animal’s body.
