A co-evolutionary theory of sleep.
Based on recent experimental evidence, a novel theory of sleep function and regulation is advanced, stating that sleep primarily evolved to protect the brain against a wakefulness-dependent increase in the permeability of the blood-brain barrier. A restitutional mechanism for the blood-brain barrier had to co-evolve against the omnipresent gut-derived bacterial cell wall constituents, because these and their elicited cellular responses increase blood-brain barrier permeability and potentially harm nervous tissue. Thus, in order to develop a highly organized cerebral structure, an immune-like response specific for the brain co-evolved during the phylogeny of the symbiosis between animals and gut bacteria to control the detrimental effects of bacterial cell wall constituents. In the course of further evolution, the sleep-associated 'controlled inflammatory state' of the brain employed the growth-factor activities of locally activated cytokines to enforce cerebral development and the maintenance of cognitive functions.
Korth
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D000818:Animals; D001419:Bacteria / Q000378:metabolism; D005075:Biological Evolution; D001812:Blood-Brain Barrier; D002473:Cell Wall / Q000378:metabolism; D003071:Cognition / Q000502:physiology; D016207:Cytokines / Q000502:physiology; D006801:Humans; D007408:Intestinal Absorption; D007422:Intestines / Q000382:microbiology; D051379:Mice; D008809:Mice, Inbred C3H; D008954:Models, Biological; D011817:Rabbits; D012890:Sleep / Q000502:physiology*; D013559:Symbiosis; D014851:Wakefulness / Q000502:physiology
D016207:Cytokines