Changes in the composition of brain interstitial ions control the sleep-wake cycle.
Level 5 - mechanism / opinion, no new human data
Preclinical animal and ex vivo laboratory research
PubMed 27126038 · doi:10.1126/science.aad4821
What was done
Researchers investigated the mechanism of sleep-wake transitions by measuring extracellular ion concentrations in tetrodotoxin-silenced mouse cortical slices exposed to neuromodulators and in vivo in mice across states of arousal, natural sleep, and anesthesia. They tracked extracellular potassium ([K+]e), calcium ([Ca(2+)]e), magnesium ([Mg(2+)]e), and proton ([H+]e) concentrations, along with extracellular volume. They also tested whether directly manipulating local cortical interstitial ion composition in sleeping mice altered electroencephalography patterns.
What was found
Neuromodulators elevated [K+]e in silenced cortical slices. In vivo arousal caused AMPA receptor-independent increases in [K+]e with concurrent decreases in [Ca(2+)]e, [Mg(2+)]e, [H+]e, and extracellular volume. Natural sleep and anesthesia showed the reverse pattern: reduced [K+]e and increased [Ca(2+)]e, [Mg(2+)]e, [H+]e, and extracellular volume. Infusing an extracellular ion mixture into the cortex of sleeping mice converted local cortical activity into the electroencephalography pattern of wakefulness. The abstract reported no specific numerical values.
Why it matters
This study indicates that changes in interstitial ion composition directly control macroscale neural state transitions, establishing ion dynamics as an active driver of the sleep-wake cycle rather than a passive byproduct of neuronal firing.
Limits
The study was conducted exclusively in mice and ex vivo brain slices, so direct applicability to human physiology remains unverified. Quantitative values, sample sizes, and potential off-target effects of the ionic infusions were not detailed in the abstract.
Cited by
- supports Sodium, potassium, and magnesium electrolytes are essential for the normal physiological function of all cells, particularly neurons.