Salts in the brain control our sleep-wake cycle

Salts in the brain control our sleep-wake cycle

Salts in our brain decide whether we are asleep or awake. For the first time, researchers have shown that the level of salts in our body and brain differ depending on whether we are asleep or awake. A new study reveals that by influencing the level of salts, it is possible to control a mouse's sleep-wake cycle. The research has just been published in the scientific journal, SCIENCE.

The researchers have used mice to test whether injecting salt into the brain enables control of the mouse's sleep-wake cycle -- independently of the so-called neuromodulators. Neuromodulators are compounds such as for example, adrenalin, which plays a decisive role in our waking up every morning.

The study shows that adrenalin and other neuromodulators change the level of salts surrounding the neurons and that the salt balance then decides whether the neurons are sensitive to stimulation in the shape of a touch. When we are awake, the salt balance makes neurons highly sensitive to stimulation, as opposed to the salt balance in the brain during sleep, where the level of salts makes it harder to activate the neurons.

Auhtors show that neuromodulators induce increases in the extracellular K+ concentration ([K+]e) in cortical slices electrically silenced by tetrodotoxin. In vivo, arousal was linked to AMPA receptor–independent elevations of [K+]e concomitant with decreases in [Ca2+]e, [Mg2+]e, [H+]e, and the extracellular volume. Opposite, natural sleep and anesthesia reduced [K+]e while increasing [Ca2+]e, [Mg2+]e, and [H+]e as well as the extracellular volume.

Local cortical activity of sleeping mice could be readily converted to the stereotypical electroencephalography pattern of wakefulness by simply imposing a change in the extracellular ion composition. Thus, extracellular ions control the state-dependent patterns of neural activity.