The purpose consists of determination of the shifts in the activity level of the noradrenergic and serotonergic central neurotransmitter systems during periodic asphyxia during sleep, as well as in the state of sleep on the background of preliminary adaptation to hypoxia. Male rats (180-220g) cortical, hippocampal, electrooculo- and electromyographic electrodes were implanted; during REM sleep, asphyxia was performed (by tightening the cuff around the neck) until awakening; repeatedly, daily for 15 days. This was an attempt to experimentally model obstructive sleep apnea. Adaptation to hypoxia was performed in a hypobaric chamber (daily for 40 days, at an "altitude of 2500 m" with an exposure of 5 hours starting from the 15th day). The concentration of norepinephrine (NE), 5-hydroxytryptamine (5-HT), and 5-hydroxyindole-3-acetic acid (5-HIAA) was determined in the tissue of the periaqueductal region of the midbrain and dorsal part of the medulla oblongata of decapitated animals using HPLC with electrochemical detection. Statistical analysis was performed using the ANOVA method. After the first day of sleep, interrupted by episodes of asphyxia in the medulla oblongata, a significant increase in the concentration of 5-HT was found compared with the control (534±27.2 vs. 439±23.4 pg/mg ww, P<0.05). After 15 days of asphyxia, an increase in the concentration of 5-HIAA was detected in the midbrain and NE in the medulla oblongata (494±19.1 vs. 407±17.6; 573±23.5 vs. 463±21.4 pg/mg, respectively). In adapted animals, after 15 days of asphyxia, the concentration of 5-HT increases and 5-HIAA decreases in the medulla oblongata compared with the group of non-adapted animals. The latent period of awakening is significantly lengthened. It can be assumed that adaptation to prior intermittent hypoxia contributes to maintaining a sufficient level of serotonin in the respiratory motor center by reducing its degradation, as well as increasing tolerance to hypoxia and/or hypercapnia, and adaptability.