Sleep is an essential part of our life and the longer we stay awake, the greater the urge to sleep becomes. Research has shown that following sleep deprivation we experience sleep that is longer and deeper than normal. The mechanism behind this has been termed sleep homeostasis. Today, we don’t have a full understanding of how this process works.

A recent study conducted by researchers at the Imperial College, London and the University of Zurich looked into the mechanism behind sleep homeostasis in mice.

Body temperature measured in sleep-deprived mice
To better understand this mechanism, mice with lesioned PO galanin neurons, as well as a control group, received an injection containing a dexmedetomidine and saline solution. Dexmedetomidine is a known long-term sedative that is commonly used in intensive care units. Despite its effectiveness, an unwanted side effect is hypothermia.

Following injection and a baseline recording period, mice were then sleep-deprived for five hours.

Throughout the study core body temperature was measured every two minutes, using Star-Oddi’s DST nano-T temperature logger. The logger was implanted into the abdominal cavity.

A common mechanism identified
Mice that had lesioned PO galanin neurons showed a reduction in sleep homeostasis. In addition, dexemedetomidine did not result in sustained hypothermia, nor did it induce high-power delta oscillations.

This implies a common mechanism behind PO galanin neurons and dexmedetomidine-induced sedation exists.

Dexmedetomidine prevents restorative sleep
The researchers conclude that it seems that dexmedetomidine over activates natural sleep homeostasis pathway resulting in deep hypothermia. It appears that when under dexmedetomidine sedation the sleep the mice experience is not restorative in the same way normal sleep is. This may be caused by the mice becoming too cold.

Going forward, understanding cellular substrates of dexmedetomidine could help in the search for sedative drugs that don’t lead to excessive cooling.

The paper was published in Current Biology and can be accessed in full here.