This work from the Beth Israel Deaconess Medical Center (Boston) identifies a “sleep switch” in the brain, which is involved in a subsidiary way in the regulation of body temperature. Very special neurons, documented in the journal Nature Communications, because when they are activated, the subject - here the mouse - is plunged into a deep sleep. A potential target, therefore, to treat sleep disorders.
About 20 years ago, the same team had already suggested that this set of nerve cells could play a key role in the onset of sleep. The team is doing it again with this new research, demonstrating in mice that these cells are indeed essential for normal sleep. It is in fact the first test that comes to activate these cells, located in a region of the hypothalamus called the ventrolateral preoptic nucleus (VLPO). And the researchers show that the activation, by laser (light) or drug (chemical activation), of these “VLPO neurons”, leads to deep sleep.
These new results confirm previous findings by the team, led by Dr. Clifford B. Saper, Chairman of the Neurology Department of the (BIDMC), that damage to these neurons can cause insomnia. One research in particular, conducted in elderly people who “lost” their VLPO neurons during the natural aging process, showed that these people suffered from insomnia.
In "normal times", these VLPO cells are stimulated 1-4 times per second, which induces sleep. If these cells are stimulated faster, they eventually fail to fire and stop functioning. Thus, activating them 10 times per second causes their function to stop completely. Finally, normal activation of VLPO cells also causes a drop in body temperature, which makes sense, since body temperature drops slightly during sleep, when VLPO neurons fire.
However, with continued activation, here in mice, body temperature drops very low, down to 5 or 6 degrees Celsius. The authors hypothesize here that excessive activation of these same neurons could be responsible for prolonged sleep and lower body temperature in hibernating animals…
