In spite of the subsequent decrease in the depth of sleep, MFV decreased further from stages IVa to IIc preceding the REM period. MFVs in stage IIa of the second and last sleep cycles were significantly (p < 0.01) lower than those in stage IIa during the first NREM cycle. A special pattern in the MFV profile was seen during passage through the second and subsequent NREM sleep cycles. MFV values were low during sleep stages

IIa and IVa following REM sleep, increased moderately during intermediate sleep stage IIb and decreased again gradually with consecutive sleep stages IIIb, IVb and IIc. The decrease in MFV values was less during the second and last NREM sleep stages than during the first sleep cycle. MFV values in all sleep stages did not differ significantly during the NREM sleep stages in the second and last NREM sleep cycles CHIR 99021 studied. The beginning of REM sleep was accompanied by a marked increase in MFV. MFV values markedly exceeded values of the preceding sleep stages II and IV but did not reach waking values in the first, second and last sleep cycle. The MFV during alpha-frequency wakefulness that follows NREM sleep was lower than waking values preceding sleep onset (Fig. 3). After morning awakening, patients lying awake often required more than half an hour to reach MFV values Trametinib corresponding to the waking state of the previous evening.

MFV profiles were occasionally interrupted by movement artifacts in all healthy subjects (Fig. 3). Rapid fluctuations in FV lasting seconds occurred during SWS as well as stage II and REM sleep. Fig. 4 shows the FV curve with corresponding sleep stages in a typical healthy

subject [39]. There were no major fluctuations of FV during stage IV. Moderate fluctuations appeared during sleep stage II. During REM sleep, the amplitude and the duration of fluctuations were markedly increased. Large fluctuations in FV lasting seconds were accompanied G protein-coupled receptor kinase by fluctuations in blood pressure. However, the changes in peripheral blood pressure and pulse were not always accompanied by corresponding changes in FV. Fluctuations in FV also occurred following sleep events such as K-complexes and arousal. Immediately after the sleep event there was a moderate increase followed by a pronounced decrease in MFV. During REM sleep, increases in velocity that appeared during phases of rapid eye movements (phasic REM) often persisted for several minutes. Fig. 5, showing a typical recording of about 6 min duration during sleep stage II, illustrates FV fluctuations that correlated with cardiovascular and respiratory parameters. K-complexes and arousal initiated the observed alterations in FV, MFV, blood pressure and CO2. Blood pressure increased in the subsequent cardiac cycles, reaching a maximum after about 5 s, then returned to normal during the next 5–15 s. Increases in MFV did not always occur despite rising blood pressure in stage II but were usually found with greater rises of blood pressure in REM sleep.