The association between the nocturnal sleep gate and nocturnal onset of urinary 6-sulfatoxymelatonin.

The present study investigated the relationship between the time of nocturnal onset of urinary 6-sulfatoxymelatonin (aMT6s) secretion, and the timing of the steepest increase in nocturnal sleepiness ("sleep gate"), as determined by an ultrashort sleep-wake cycle test (7 min sleep, 13 min wake). Twenty-nine men (mean age 23.8 +/- 2.7 years) participated. The ultrashort sleep-wake paradigm started at 0700 hr after a night of sleep deprivation and continued for 24 hr until 0700 hr the next day. Electrophysiological recordings were carried out during the 7-min sleep trials, which were then scored conventionally for sleep stages. Urinary aMT6s was measured every 2 hr. The results showed that the timing of the sleep gate was significantly correlated with the onset of aMT6s secretion. These results are discussed in light of the possible role of melatonin in sleep-wake regulation.

Periodic, profound peripheral vasoconstriction--a new marker of obstructive sleep apnea.

We report a novel approach to the determination of sleep apnea based on measuring the peripheral circulatory responses in a primary condition of disordered breathing. The apparatus is a finger plethysmograph coupled to a constant volume, variable pressure, pneumatic system. The plethysmograph's tip (measurement site) is composed of two parallel opposing longitudinal half thimbles, which is attached to a contiguous annular cuff. Each compartment consists of an internal membrane surrounded by an outer rigid wall. These provide a uniform pressure field and impart a two-point locking action preventing axial and longitudinal motion of the finger. Subdiastolic pressure is applied to prevent venous pooling, engorgement, and stasis, to inhibit retrograde venous shock wave propagation and partially unload arterial wall tension. The annular cuff extends the effective boundary of the pressure field beyond the measuring site. In 42 patients with Obstructive Sleep Apnea Syndrome (OSAS) profound, transient vasoconstriction and tachycardia usually of a periodic nature, were clearly seen with each apneic event, possibly related to transient arousal. Good agreement was found between standard total apnea-hypopnea scoring, 129.5+/-22.4 (Mean +/- SEM), and transient vasoconstriction and tachycardia events, 121.2+/-19.4 (R = .92, p<.0001). We conclude that the finger tip exemplifies the scope of peripheral vascular responsiveness due to its high density of alpha sympathetic innervation, and its high degree of blood flow rate lability. Given that elevated peripheral resistance and tightly linked transient heart rate elevation is a consistent part of the hemodynamic response to arousal and OSAS, we believe that pulsatile finger blood flow patterns can be clearly diagnostic of OSAS and other sleep-disordered breathing conditions.

Power spectrum analysis and heart rate variability in Stage 4 and REM sleep: evidence for state-specific changes in autonomic dominance.

The present study investigated autonomic activity during NREM and REM sleep stages and wakefulness by spectral analysis of heart rate variability. The results demonstrated that NREM sleep in humans was characterized by a widely different autonomic activation pattern than REM sleep: high parasympathetic activity was found in NREM, while REM was characterized by attenuated vagal tone, and augmented sympathetic activity. The overall pattern during wakefulness showed an intermediate position between NREM and REM patterns; parasympathetic activity was lower than in NREM and higher than in REM, with an opposite trend for sympathetic activity.

Hypnotic and hypothermic effects of melatonin on daytime sleep in humans: lack of antagonism by flumazenil.

In this double-blind, placebo-controlled study we investigated whether 10 mg flumazenil, a pure benzodiazepine antagonist, can block the hypnotic and hypothermic effects of 3 mg melatonin. The design comprised four 7-h (1200-1900 h) testing periods, preceded by a 'no-treatment' adaptation period of the "7/13' sleep-wake paradigm. Six young healthy adult males were paid to participate. During each experimental period, tablets were administered at 1145 h (flumazenil or placebo) and at 1200 h (melatonin or placebo) in a randomized, double-blind, partially repeated Latin square design. Polysomnographic recordings and core body temperature recordings revealed that melatonin, either in combination with placebo or with flumazenil, significantly increased the amounts of sleep, and decreased core body temperature in comparison with placebo alone or the combination of flumazenil plus placebo. These results do not support the hypothesis that melatonin exerts its hypothermic and hypnotic effects via the central benzodiazepine receptors.

Cardiac autonomic function during sleep in psychogenic and organic erectile dysfunction.

The present study investigated the sympathetic/parasympathetic balance during non-rapid eye movement (NREM) and rapid eye movement (REM) sleep in patients with psychogenic and organic erectile dysfunction. The cardiac autonomic balance was assessed from the power of the low frequency (LF) and high frequency (HF) spectral components of heart-rate variability in 11 patients with psychogenic erectile dysfunction and 11 patients with organic erectile dysfunction as determined by monitoring sleep-related erections. Spectral analysis of heart-rate variability was calculated for at least four successive 4-min epochs of electrocardiogram recordings during NREM sleep and for all available 4-min epochs during REM sleep. Statistical analysis revealed that organic patients had a significantly higher LF/HF ratio (P < 0.01) during both stages of sleep, which resulted from a significantly lower power in the HF component (P < 0.004) and higher power in the LF component (P < 0.01) in these patients, in both REM and NREM sleep stages. These results demonstrate that patients complaining of daytime sexual dysfunction and found by sleep-related erection monitoring to suffer from organic erectile dysfunction, have altered cardiac autonomic balance during both stages of sleep.

Alterations in R-R variability associated with experimental motion sickness.

Motion sickness is a complex integration of responses from multiple physiological systems. Whether the changes that occur during the time course of motion sickness are mediated by the sympathetic or parasympathetic systems is still controversial. The present study evaluates alterations in R-R variability during experimental motion sickness in motion sick and non-motion sick subjects. Ten motion sick subjects and 7 non-motion sick subjects participated in the study. Power spectrum analysis of R-R variation was conducted for all subjects 10 min before a brief vestibular disorientation test (BVDT), for 5-10 min of the test, and 10 min after the test. Subjects were also asked to report their symptoms during the test. The motion sick group showed a significant reduction in the power spectrum density of the R-R interval at the mid and high frequencies during the BVDT test period (BVDT), in comparison with the rest period (Rest). These changes probably indicate a decrease in parasympathetic activity during the time course of motion sickness. The non-motion sick group did not show significant differences at any of the frequencies during BVDT. Power spectrum analysis of the R-R interval provides an objective measure of the autonomic response to experimental motion sickness.