Stress hormone, and not neurons, manage the fixed circadian rhythm that controls everything from sleep needs to body temperature, the researchers have found.
Our internal clock is controlled by some very distinct hereditary genes, known as clock genes. These genes are particularly active in the so-called suprachiasmatic nucleus area of the brain.
However, these areas of the brain are not directly linked by neurons, and this made researchers at the University of Copenhagen curious.
Using lab tests, the team demonstrated that the circadian rhythm is controlled by the stress hormone, corticosterone.
"In humans, the hormone is known as cortisol, and although the sleep rhythm in rats is the opposite of ours, we basically have the same hormonal system," said Associate Professor Martin Fredensborg Rath from the Department of Neuroscience.