La Función del Sueño: Mantener la Integridad de los Sistemas de Protección y Limpieza del Cerebro

Sleep is a vital function for organisms. Pioneering studies carried out in the 1980s showed that sleep is essential to guarantee the survival of the species. Since then, numerous experiments have been carried out to elucidate the function of sleep; Despite the accumulation of evidence, a widely accepted consensus has not been generated in this regard. Our group has proposed that the function of sleep is to maintain reciprocal interactions between systems that maintain homeostasis, the nervous, endocrine and immune systems. In the particular case of the nervous system, the systems responsible for maintaining homeostasis are the blood-brain barrier and the lymphatic system. The blood-brain barrier is located at the level of the brain capillaries, is made up of brain endothelial cells. The barrier phenotype of brain endothelial cells depends on cell-cell interactions with pericytes and on soluble factors released by astroglia. The lymph system promotes the exchange of solutes between the interstitial fluid of the brain and the cerebrospinal fluid at the level of the perivascular spaces. In the last decade, it has been described that both systems present changes in their physiology in response to variations in local synaptic activity; In particular, it has been described that the great changes in brain electrical activity associated with the sleep / wake cycle modify the functioning of both systems. In the case of the lymphatic system, it has been described that during slow sleep the rate of solute exchange from interstitial fluid to cerebrospinal fluid increases. While in the case of the blood-brain barrier, a reduction in the expression of occludent binding proteins has been shown, which is reflected in an increase in the permeability to soluble molecules circulating in the blood.