Stage 2 Research Articles

Comparison of the effects of zolpidem and triazolam on nocturnal sleep and sleep latency in the morning: A cross-over study in healthy young volunteers

1. 1. Zolpidem (ZPD, 10mg) was directly compared with triazolam (TRZ, 0.25mg), a benzodiazepine hypnotic of a short action comparable to ZPD. The compounds were given to healthy young subjects for three nights, in a crossover design. 2. 2. Polysomnographic data of three 150-min sections of the nights as well as the whole nights were analyzed, to clearly detect the proper effects of the very short acting hypnotics, which might be missed in the analysis of whole night. 3. 3. Time courses were significantly different between the two compounds in the ratios (%) of stage wake (SW), stage 2 (S2), slow wave sleep (SWS) and stage REM (SR). 4. 4. Compared to the baseline, SWS was increased by ZPD on the first night, not by TRZ. The separate analysis of the three 150-min sections revealed an increase of SWS during the first 150-min of the ZPD night, suggesting a proper action of ZPD to augment SWS. An increase of S2 and a decrease of SR were caused by TRZ, not by ZPD. However, the separate analysis indicated that ZPD might reduce SR during the first 150-min, which was cancelled by a subsequent rebound increase in the whole night analysis. 5. 5. During the withdrawal period, TRZ, not ZPD, increased SW and SR with worsening of mood in the morning. ZPD did not affect sleep latency in the morning, while TRZ caused a trend of the reduction.

Effects of inhaled carbon dioxide and oxygen on cheyne-stokes respiration in patients with heart failure.

We hypothesized that in patients with congestive heart failure (CHF), reductions in PaCO2 sensed at the peripheral chemoreceptors trigger central apneas during Cheyne-Stokes respiration (CSR-CSA), and that raising PaCO2 by inhalation of a CO2 would eliminate these events. The effects of CO2 inhalation on the frequency of apneas and hypopneas during stage 2 (S2) sleep were studied in 10 CHF patients with CSR-CSA. The time from the breath with the minimal end tidal fraction of CO2 (FETCO2) during hyperpnea until the onset of apnea correlated strongly with the lung to ear circulation time (LECT) (r2 = 0.90, p < 0.0001), a measure of lung to carotid body circulatory delay. Among the six patients who also inhaled O2, CO2 inhalation increased transcutaneous PCO2 (PtcCO2) (36.4 +/- 4.6 mm Hg versus 38 +/- 4.4 mm Hg, p < 0.002), abolished central apneas and hypopneas (43.0 +/- 8.4 per hour on air versus 1.6 +/- 2.6 per hour on CO2, p < 0.0001), and increased SaO2. In contrast, O2 inhalation causing a similar rise in SaO2 had no significant impact on either PtcCO2 or the frequency of central events. We conclude that central apneas in patients with CHF are triggered by a low PaCO2 most likely sensed at the peripheral chemoreceptors, and that inhalation of CO2 reverses central apneas by raising PaCO2.

Neurotoxic N-methyl- d-aspartate lesion of the ventral midbrain and mesopontine junction alters sleep–wake organization

The dorsal regions of the midbrain and pons have been found to participate in sleep regulation. However, the physiological role of the ventral brainstem in sleep regulation remains unclear. We used N-methyl- d-aspartate-induced lesions of the ventral midbrain and pons to address this question. Unlike dorsal mesencephalic reticular formation lesions, which produce somnolence and electroencephalogram synchronization, we found that ventral midbrain lesions produce insomnia and hyperactivity. Marked increases in waking and decreases in slow wave sleep stage 1 (S1), stage 2 (S2) and rapid eye movement sleep were found immediately after the lesion. Sleep gradually increased, but never returned to baseline levels (baseline/month 1 post-lesion: waking, 30.6±4.58%/62.3±10.1%; S1, 5.1±0.74/3.9±1.91%; S2, 46.2±4.74%/23.1±5.47%; rapid eye movement sleep, 14.1±3.15%/7.2±5.42%). These changes are comparable in magnitude to those seen after basal forebrain lesions. Neuronal degeneration was found in the ventral rostral pons and midbrain, including the substantia nigra, ventral tegmental area, retrorubral nucleus, and ventral mesencephalic and rostroventral pontine reticular formation. We conclude that nuclei within the ventral mesencephalon and rostroventral pons play an important role in sleep regulation.

Automatic SCSB analysis of motor and autonomic nervous functions compared with sleep stages.

All-night recordings of respiration, ballistocardiogram, and body movements were obtained using the static charge-sensitive bed (SCSB) and automatically analysed data were compared with sleep stages. The mean sum of eight SCSB variability parameters was lowest in slow wave sleep (SWS), higher during stage 2 (S2), and highest in REM sleep. The sum scores of the parameters with the highest correlations with the EEG data were classified into quiet (QS), intermediate (IS) and active (AS) states. SCSB signals during wakefulness, stage 1 and REM sleep were mostly scored as AS, whereas in S2 and especially in SWS they were scored as QS or IS. The SCSB is an easy and inexpensive tool for conducting follow-up studies on sleep quality in natural environments.

Inter and intrahemispheric EEG correlation as a function of sleep cycles

Corsi-Cabrera, Maria, Miguel Angel Guevara, Consuelo Arce' and Julieta Ramos. Inter and intrahemispheric EEG correlation as a function of sleep cycles. Prog. Neuro-Psychopharmacol. & Biol. Psychiat., 1996, 20. 1. 1. Inter (INTERr) and intrahemispheric (INTRAr) EEG correlation were assessed in 8 young male adults during wakefulness (W) with eyes closed before going to sleep and during stage 2 (S2), stage 4 (S4) and paradoxical sleep (PS) of the first three sleep cycles during the second night spent at the laboratory. 2. 2. Pearson product-moment correlation were calculated between EEG signals of each pair of electrodes (C3, C4, F3, F4, T3, T4) for every 0.5 Hz from 1.5 to 15 Hz. 3. 3. INTERr and INTRAr of 1.5–6.5 and 11–15 Hz were significantly higher during stage 2 and 4, INTERr of 1.5–6.5 Hz was also higher during PS in cycle 1 and 2, whereas INTERr and INTRAr of 7–10.5 Hz were lower than during wakefulness. 4. 4. INTRAr of S2 and S4 approximated, whereas INTRAr of PS moved away from W over successive sleep cycles. 5. 5. These data show that cortical changes during sleep are also observed in functional differentiation between cortical sites. Inter and intrahemispheric differentiation is attenuated during stage 2 and 4 while during PS only interhemispheric differentiation is attenuated but intrahemispheric differentiation is accentuated compared to wakefulness. This pattern of cortical differentiation may be of relevance for the understanding of mental activity changes during sleep.

Plant Water Status and Fruit Quality in `Braeburn' Apples

Five-year-old `Braeburn' apple trees (Malus domestica Borkh.) on MM.106 rootstock were studied to determine plant and fruit quality responses to reduced plant water status late in the season. Trees were irrigated or not irrigated. Those not irrigated developed reduced xylem water potential and stomatal conductance from 110 and 132 days after full bloom (DAFB), respectively. However, they showed no reduction in photosynthetic rates. Fruit were harvested at stage 1 (S1), starting 167 DAFB, or stage 2 (S2), starting 180 DAFB. At S1, fruit had higher soluble solids concentrations, enhanced red skin pigmentation, and a tendency for higher sorbitol concentrations. Total soluble sugar concentrations at final harvest showed no difference between treatments, but fruit from the nonirrigated trees showed earlier sugar accumulation during the season. Such fruit also had reduced Ca+2 concentrations at S1 and S2 relative to those on plants that were irrigated. No incidence of any disorder was found in fruit from either treatment at harvest or after 12 weeks of 0C storage.

Overnight growth hormone secretion in short children: independence of the sleep pattern.

to analyze the interrelationships between GH secretion and pattern of sleep. 18 children (10 male, 8 female; mean age 9.1 yr, range 5.1-14.3 yr), with short stature (mean height standard deviation score (SDS) -2.52, range -3.86-(-)1.88; mean height velocity SDS -1.1, range -2.40-(-)0.08), including 9 children with genetic short stature and 9 with idiopathic short stature. blood samples were taken every 15 min from 2000 h-0800 h, and GH profiles were analyzed by the PULSAR computerized peak identification algorithm; simultaneous sleep was analyzed by electroencephalogram recording. no significant correlation was noted between GH secretion parameters and any of the electroencephalogram parameters evaluated: stage 1 (S1) percent, stage 2 (S2) percent, slow-wave sleep (SWS) percent, rapid eye movement sleep percent, wakefulness (W) percent, and sleep efficiency (EFF); there was no significant difference in GH secretion between children with EFF less than 76% and those with EFF more than 76% (P > 0.5). Maximal GH peak coincided 9 times (50%) with SWS, 3 times (17%) with S2, 3 times with W, twice (11%) with S1, and once (6%) with rapid eye movement sleep. First GH peak coincided 12 times (67%) with W, 3 times with S2, twice with SWS, and once with S1. There was no significant difference comparing the percentage of sleep stages occurring in the 15 min of maximal GH increment, in the 15 min preceding it, and in those following it; there was no significant difference comparing the percentage of sleep stages occurring in the 15 min preceding the onset of a GH peak and in those following it. GH secretion in short children seems independent of the sleep stage and efficiency; in children it is possible that GH secretion relates with sleep per se and with neurohormonal changes occurring at nighttime rather than with a specific sleep stage or sleep stage sequence.

A starvation test to determine optimal salinities for larval freshwater prawns, Macrobrachium rosenbergii

1. 1. A starvation test was conducted in small beakers with stage 1 (S1) and stage 2 (S2) Macrobrachium rosenbergii larvae to determine optimal salinities. 2. 2. Experiments were first performed with S2 larvae at 13 ppt to identify a suitable medium made with artificial sea salts. 3. 3. A broad-range (0–35 ppt) and a subsequent narrow-range (9–16 ppt) salinity experiment with S2 larvae were used to identify 13 ppt as the optimal salinity, with 12 ppt as the next best; this agrees well with most previous estimates of optimal salinities for rearing larvae. 4. 4. S1 larvae were also tested in a narrow-range salinity experiment but were not used further because, unlike starved S2 larvae, they molted during the experiment. 5. 5. Identification of the optimal salinity was not affected by 50% daily water exchange or by bright light. 6. 6. Exposure of larvae to three different salinities—7, 13 and 19 ppt—during S1 influenced the width of the optimal salinity range for S2 larvae.

A dose-response study of sleep loss and spontaneous sleep termination.

ABSTRACTRecent concepts of sleep/wake regulation have emphasized circadian influences and largely disregarded homeostatic ones. The present experiment was designed to study sleep loss homeostasis while minimizing confounding circadian influences. Eight male subjects participated in the study. Night sleep was curtailed across four conditions to yield 0, 2, 4, or 8 hrs of sleep. The effects were studied on subsequent day sleep begun at 1100h and spontaneously terminated. Total sleep time (TST), Stage 2 (S2), and Stages 3+4 (SWS) showed very strong dose‐dependent increases with increasing loss. REM sleep did not respond. After maximum sleep loss TST and S2 doubled whereas SWS increased fivefold. Sleep did not terminate until the prior loss of SWS had been recovered. The total SWS recovery approximately matched the loss. TST, S2, and REM failed to recover more than limited amounts of the loss. The results show that homeostatic influences on sleep may be much larger than usually acknowledged and that SWS closely, although not perfectly, reflects the “active component’ of sleep homeostasis.

Comparison of Sleep Characteristics of Subjects in Their 70's with Those in Their 80's

This study was undertaken to examine the effect of aging on sleep. All-night sleep polygrams of 15 subjects in their 70's and 11 subjects in their 80's were recorded for three consecutive nights. The increase in stage wakefulness (SW) and the decrease in stage 2 (S2) were significant in the subjects in their 80's in comparison with those in their 70's (p less than 0.05, P less than 0.01, respectively). After the age of 70, slow wave sleep decreased in the earlier part of the night and REM sleep shifted to the earlier part of the night. These facts support the hypothesis that slow wave sleep and REM sleep compete with each other.