[SLOW-WAVE SLEEP AND MOLECULAR CHAPERONES].

From ancient times the mankind has been interested in a topical issue: why is it necessary to spend about one-third of human life for sleep? This review considers the main data on the key function of slow-wave sleep (SWS) and the molecular mechanisms of its regulation; the basic conclusions are presented below as a summary and hypotheses. 1. SWS has an energy-conserving function developed simultaneously with the evolution of tachimetabolism and endothermy/homoiothermy. 2. The most significant reduction of energy demands in the brain occurs during the deep SWS (characterized by increased EEG-delta power), thus creating the optimal conditions for enhancing anabolic processes and realizing the key biological function of sleep--the increase in protein synthesis rate in the brain. 3. The conditions of the paradoxical sleep (PS) as an 'archeowakefulness' state, containing the elements of endogenous stress, seem to be acceptable for expression of chaperones required for repairing misfolded proteins newly synthesized during the deep SWS. 4. The close integration of two molecular systems, HSP70 and HSP40, contained in the sleep 'center' in the preoptic area of the hypothalamus, and their compensatory interrelations contribute significantly to the maintenance of sleep homeostasis and to implementation of its functions under non-stress conditions and during long-term deficiency of chaperones in the brain that is intrinsic for aging and various neuropathologies. 5. Occurring daily throughout the lifetime cyclical changes of the protein synthesis rate (during the deep SWS) and the expression of HSP70 chaperonez (during wakefulness and, possibly, during PS) are crucial for functions of homeothermic organisms, including recuperation of the nervous system's structure and functions.