Sleep and wakefulness in Callorhinus ursinus

Sleep and wakefulness of northern fur seals were studied on three subadult bulls carrying the implanted electrodes for recording the electrocorticogram of the two hemispheres, the neck electromiogram, the electrooculogram and the electrocardiogram. The active wakefulness accounted for 32.0 +/- 5.3% of total recording time, the relaxed wakefulness -31.7 +/- 3.1%, the slow wave sleep -30.5 +/- 5.1% and the paradoxical sleep -5.8 +/- 0.9%. The sleep cycle averaged 22,6 +/- 1.2 minutes. Interhemispheric asymmetry of the ECoG slow waves was pronounced in all three animals. Different forms of the asymmetry occupied 15.0 +/- 0.7% of total recording time. Such interhemispheric asymmetry was found in pinnipeds for the first time, in this respect the northern fur seals differ from the Caspean seals but resemble the dolphins.     

An EEG study of different behavioral states of freely moving dolphins]

ECoG and EMG of neck and eye muscles of four free moving dolphins were recorded during sleep-wakefulness cycle through chronically implanted electrodes. Wakefulness is accompanied by desynchronized ECoG, and slow sleep by synchronized ECoG, including the sleep spindles and theta- and delta-waves. The standard EMG criteria do not allow the discrimination between fast sleep and wakefulness in dolphins. Behavioral observations alone do not inform about dolphin's sleep or wakefulness. The respiration of dolphins may be observed during bilateral ECoG synchronization in slow sleep without arousal. ECoG synchronization as well as desynchronization may be observed when the contralateral eye is open.     

Sleep and wakefulness in the green iguanid lizard (Iguana iguana)

The reptile Iguana iguana exhibits four states of vigilance: active wakefulness (AW), quiet wakefulness (QW), quiet sleep (QS) and active sleep (AS). Cerebral activity decreases in amplitude and frequency when passing from wakefulness to QS. Both parameters show a slight increase during AS. Heart rate is at a maximum during AW (43.8+/-7.9 beats/min), decreases to a minimum in QS (25.3+/-3.2 beats/min) and increases in AS (36.1+/-5.7 beats/min). Tonical and phasical muscular activity is present in wakefulness, decreases or disappears in QS and reappears in AS. Single or conjugate ocular movements are observed during wakefulness, then disappear in QS and abruptly reappear in AS. Although these reptiles are polyphasic, their sleep shows a tendency to concentrate between 20:00 and 8:00 h. Quiet sleep occupies the greater percentage of the total sleep time. Active sleep episodes are of very short duration, showing an average of 21.5+/-4.9 (mean+/-SD). Compensatory increment of sleep following its total deprivation was significant only for QS. Reaction to stimuli decreased significantly when passing from wakefulness to sleep. It is suggested that the lizard I. iguana displays two sleep phases behaviorally and somatovegetatively similar to slow wave sleep and paradoxical sleep in birds and mammals.     

侧脑室注射促甲状腺激素释放激素对大鼠睡眠—觉醒的影响

采用多导睡眠描记术研究了例脑室注射促甲状腺激素释放激素(TRH)对正常大鼠和去甲状腺大鼠睡眠-觉醒的影响。在正常大鼠,TRH引起觉醒增加,浅慢波睡眠(SWS_1)、深慢波睡眠(SWS_2)和总睡眠时间(TST)均减少,异相睡眠(PS)消失,SWS_1、SWS_2和PS的潜伏期均显著延长,给药后立即产生效应并在1h内达高峰。去甲状腺对大鼠的睡眠-觉醒无明显影响,注射TRH后引起的效应与正常大鼠相似。结果提示TRH有促进大鼠觉醒的作用,对各睡眠时相均有抑制作用,其作用部位可能在下丘脑以外的中枢结构。     

Sleep pattern in the starling (Sturnus vulgaris)

Electrographic and behavioural observations were conducted on two male and two female captive starlings (Sturnus vulgaris) under natural illumination conditions during autumn. Polygraphically sleep and wakefulness of starling were similar to those of other birds. Starling's total sleep (TS) and slow wave sleep (SWS) lasted 39.0 +/- 1.4% and 38.3 +/- 1.7% of the 24-h period respectively. Paradoxical sleep (PS) was 1.8 +/- 0.2% of the total sleep time. The mean durations individual of TS, SWS and PS episodes were 6.8 +/- 0.2 min, 5.0 +/- 1.0 min and 18 +/- 3 s respectively. The daily percentage of SWS was correlated with the mean episode duration while that of PS was correlated with the number of episodes rather than with the mean episode duration. Starling females spent in sleep a greater percentage of the 24-h period than males.     

Evidence for the involvement of alpha-2 adrenoceptors in the sedation but not REM sleep inhibition by clonidine in the rat

Rats with implanted electrodes for recording of EEG and EMG underwent 12-h recordings during the light period starting after i.p. injections of clonidine (0.1 mg/kg) alone or in combination with different alpha-adrenoceptor antagonists. Clonidine increased the proportion of time the rats spent in the drowsy stage of wakefulness which corresponds to behavioural sedation and inhibited both deep slow wave sleep and REM sleep for 6-9 hours. The amount of active wakefulness or light slow wave sleep were unaffected by clonidine. Yohimbine (1 mg/kg) reversed the increase in drowsy wakefulness by clonidine and increased active wakefulness without affecting sleep. Phentolamine (10 mg/kg) was ineffective against clonidine. Phenoxybenzamine (20 mg/kg) accentuated the sedative effect and prolonged the REM sleep inhibiting effect of clonidine. Prazosin (3 mg/kg) prolonged both the drowsy stage inducing and deep slow wave plus REM sleep inhibiting effects of clonidine. These electrophysiological results support the view that the sedative effect of clonidine in the rat is mediated by alpha-2 adrenoceptors, whereas in this species other mechanisms, possibly another population of alpha-2 receptors, may be involved in the clonidine-induced suppression of deep slow wave sleep and REM sleep.     

Respiratory chemosensitivity during wake and sleep in harbour seal pups (Phoca vitulina richardsii)

In this study, we examined the cardiorespiratory patterns of harbour seal pups under normoxic/normocarbic (air), hypoxic/normocarbic (15%, 12%, and 9% O2 in air), and normoxic/hypercarbic (2%, 4%, and 6% CO2 in air) conditions while awake and sleeping on land. Animals were chronically instrumented to record electroencephalogram (EEG), electromyogram (EMG), and electrocardiogram (EKG) signals, which, along with respiration (whole-body plethysmography) and oxygen consumption (VO2), were recorded from animals breathing each gas mixture for 2-4 h on separate days. Our results show that for animals breathing air, VO2 was not significantly lower during slow-wave sleep (SWS; 7.71 +/- 0.39 mL O2 min(-1) kg(-1); all measurements are mean +/- SEM) than during wakefulness (WAKE; 8.80 +/- 0.25 mL O2 min(-1) kg(-1)) and was unaffected by changes in respiratory drive. Although there was no significant fall in VO2 associated with a decrease in arousal state, breathing frequency (f(R)) did decrease (from 18.80 +/- 1.50 breaths min(-1) in WAKE to 10.40 +/- 0.49 breaths min(-1) in SWS), while the incidence of long apneas (>20 s) increased (12.76 +/- 4.06 apneas h(-1) in WAKE and 31.95 +/- 2.37 apneas h(-1) in SWS). Breathing was rarely seen during rapid eye movement (REM) sleep. Tachypnea was present at all levels of increased respiratory drive; however, hypoxia induced a dramatic bradycardia regardless of arousal state, while hypercarbia produced a tachycardia in SWS only. The hypoxic and hypercarbic chemosensitivities of harbour seal pups were similar to those of terrestrial mammals; however, unlike terrestrial mammals, where hypoxic and hypercarbic sensitivities are often reduced during SWS, the sensitivity of harbour seal pups to hypoxia and hypercarbia remained unchanged during the decrease in arousal state from WAKE to SWS.     

States of rest and activity in the Commerson's dolphin <Emphasis Type="Italic">Cephalorhynchus commersonii</Emphasis>

The unihemispheric slow-wave sleep, the ability to sleep during swimming with one open eye and the absence of paradoxical sleep in its form observed in all terrestrial mammals are unique features of sleep in cetaceans. Visual observation supplement electrophysiological studies and allow obtaining novel data about sleep of cetaceans. In the present study we examined behavior of 3 adult Commerson's dolphins Cephalorhynchus commersonii kept in the oceanarium Sea World (San Diego, CA, USA). The behavior of the dolphins can be subdivided into 5 swimming types: (1) active swimming marked by variable and irregular trajectory of movement (for 3 dolphins, on average, 35.1 ± 2.7% of the 24-h period) was the active wakefulness; (2) circular swimming was divided into the slow and fast swimming and occupied, on average, 44.4 ± 3.8 and 9.7 ± 0.8% of the 24-h period, respectively; during the circular swimming, dolphins performed from 1 to 6 circular swimming during one respiration pause; (3) quiet chaotic swimming (3.9 ± 1.2%) that occurred at the bottom and was not accompanied by signs of activity; (4) hanging, and (5) slow swimming at the surface (4.1 ± 0.5 and 2.8 ± 0.4%) respectively; the latter two swimming types were accompanied by frequent respiration (hyperventilation). We suggest that the sleep state in Commerson's dolphins occurs predominantly during the circular and quiet swimming. From time to time the dolphins decreased the speed, up to complete stop. Such episodes appeared to be the deepest sleep episodes. In all dolphins, muscle jerks as well erection in male are observed. Most jerks and erections occurred during the circular and quiet chaotic swimming. Thus, Commerson's dolphins, like other studied small cetaceans, are swimming for 24 h per day and they sleep during the swimming. Some muscle jerks that were observed in the dolphins in this study might have been brief episodes of paradoxical sleep.     

Neuromuscular and mechanical responses to inspiratory resistive loading during sleep

The purposes of this study were 1) to characterize the immediate inspiratory muscle and ventilation responses to inspiratory resistive loading during sleep in humans and 2) to determine whether upper airway caliber was compromised in the presence of a resistive load. Ventilation variables, chest wall, and upper airway inspiratory muscle electromyograms (EMG), and upper airway resistance were measured for two breaths immediately preceding and immediately following six applications of an inspiratory resistive load of 15 cmH2O.l-1 X s during wakefulness and stage 2 sleep. During wakefulness, chest wall inspiratory peak EMG activity increased 40 +/- 15% (SE), and inspiratory time increased 20 +/- 5%. Therefore, the rate of rise of chest wall EMG increased 14 +/- 10.9% (NS). Upper airway inspiratory muscle activity changed in an inconsistent fashion with application of the load. Tidal volume decreased 16 +/- 6%, and upper airway resistance increased 141 +/- 23% above pre-load levels. During sleep, there was no significant chest wall or upper airway inspiratory muscle or timing responses to loading. Tidal volume decreased 40 +/- 7% and upper airway resistance increased 188 +/- 52%, changes greater than those observed during wakefulness. We conclude that 1) the immediate inspiratory muscle and timing responses observed during inspiratory resistive loading in wakefulness were absent during sleep, 2) there was inadequate activation of upper airway inspiratory muscle activity to compensate for the increased upper airway inspiratory subatmospheric pressure present during loading, and 3) the alteration in upper airway mechanics during resistive loading was greater during sleep than wakefulness.     

Ventilatory long-term facilitation in mice can be observed during both sleep and wake periods and depends on orexin.

Respiratory long-term facilitation (LTF) is a long-lasting (>1 h) augmentation of respiratory motor output that occurs even after cessation of hypoxic stimuli, is serotonin-dependent, and is thought to prevent sleep-disordered breathing such as sleep apnea. Raphe nuclei, which modulate several physiological functions through serotonin, receive dense projections from orexin-containing neurons in the hypothalamus. We examined possible contributions of orexin to ventilatory LTF by measuring respiration in freely moving prepro-orexin knockout mice (ORX-KO) and wild-type (WT) littermates before, during, and after exposure to intermittent hypoxia (IH; 5 x 5 min at 10% O2), sustained hypoxia (SH; 25 min at 10% O2), or sham stimulation. Respiratory data during quiet wakefulness (QW), slow wave sleep (SWS), and rapid-eye-movement sleep were separately calculated. Baseline ventilation before hypoxic stimulation and acute responses during stimulation did not differ between the ORX-KO and WT mice, although ventilation depended on vigilance state. Whereas the WT showed augmented minute ventilation (by 20.0 +/- 4.5% during QW and 26.5 +/- 5.3% during SWS; n = 8) for 2 h following IH, ORX-KO showed no significant increase (by -3.1 +/- 4.6% during QW and 0.3 +/- 5.2% during SWS; n = 8). Both genotypes showed no LTF after SH or sham stimulation. Sleep apnea indexes did not change following IH, even when LTF appeared in the WT mice. We conclude that LTF occurs during both sleep and wake periods, that orexin is necessary for eliciting LTF, and that LTF cannot prevent sleep apnea, at least in mice.     

Central mechanisms of the sleep-wakefulness cycle control

The notions on the anatomical, physiological and neurochemical mechanisms of the regulation of wakefulness, slow wave (NREM) sleep and paradoxical (REM) sleep formed by the end of the first decade of the 21st century are briefly reviewed.     

Central mechanisms of sleep-wakefulness cycle

Brief anatomical, physiological and neurochemical basics of the regulation of wakefulness, slow wave (NREM) sleep and paradoxical (REM) sleep are regarded as representing by the end of the first decade of the second millennium.     

The English bulldog: a natural model of sleep-disordered breathing

To establish a natural model of sleep-disordered breathing, we investigated respiration during wakefulness and sleep in the English bulldog. This breed is characterized by an abnormal upper airway anatomy, with enlargement of the soft palate and narrowing of the oropharynx. During sleep, the animals had disordered respiration and episodes of O2 desaturation. These were worst in rapid-eye-movement (REM) sleep, with most bulldogs having O2 saturations of less than 90% for prolonged durations. In contrast, control dogs never desaturated. In REM sleep, the bulldogs had episodes of both central and obstructive apnea, the latter being associated with paradoxical movements of the rib cage and abdomen. During wakefulness, the bulldogs were hypersomnolent as evidenced by a shortened sleep latency (mean of 12 min compared with greater than 150 min for controls). This animal model should facilitate studies of the natural history of the sleep apnea syndrome and its complications.     

Dynamics of neuronal activity in the posterior hypothalamus during alternating phases of the sleep-wake cycle

The dynamics of neuronal activity in the posterior hypothalamus in different phases of the sleep-wake cycle were investigated during experiments on free-ranging cats. The highest frequency discharges were found to occur in 89.3% of neurons belonging to this region during the stages of active wakefulness and emotionally influenced paradoxical sleep. These neurons become less active during restful wakefulness and the unemotional stage of paradoxical sleep; this reduced activity can be most clearly observed in the context of slow-wave sleep. It was found that 7.1% of test neurons discharged at the highest rate during the stage of active wakefulness. They did not achieve an activity level characteristic of active wakefulness during the period of paradoxical sleep, although activity level was higher than during other states. Only 3.6% of neurons followed the opposite pattern, with discharges succeeding more frequently in slow-wave sleep and activity reduced to an equal degree during wakefulness and paradoxical sleep. The neurophysiological mechanisms governing the sleep-wake cycle and how the posterior hypothalamus contributes to these mechanisms are discussed.I. S. Beritashvili Institute of Physiology, Academy of Sciences of Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 160–167, March–April, 1988.     

Temporal patterns of unit activity of mesencephalic reticular nuclei during sleep and waking

Temporal patterns of unit activity in the mesencephalic reticular nuclei (n. cuneiformis, n. parabrachialis) were studied in unrestrained rats during the sleep-waking cycle; activity was derived by means of movable metallic microelectrodes. Analysis of the data showed that most neurons of these mesencephalic reticular nuclei (76 and 66% respectively) generate activity with the highest frequency during active waking and the emotional stage of paradoxical sleep; they discharge with lower frequency during passive wakefulness and the nonemotional stage of paradoxical sleep, and they exhibit least activity during slow-wave sleep. Comparatively few neurons (24 and 15%) demonstrate the opposite kind of temporal pattern of activity: They discharge more intensively during slow-wave sleep and more slowly during active wakefulness and the emotional stage of paradoxical sleep. Activity of these neurons during quiet wakefulness and the nonemotional stage of paradoxical sleep reaches the level of activity observed during slow-wave sleep. Neurons discharging intensively during active wakefulness were found in n. parabrachialis; their discharge frequency during passive wakefulness and slow-wave sleep and its frequency was least during paradoxical sleep. The similarity and differences of the neurophysiological mechanisms of regulation of the phases and stages of the sleepwaking cycle are discussed.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 16, No. 5, pp. 678–690, September–October, 1984.     

Evolutionary aspects of sleep–wake cycle development in vertebrates (Modern state of the I.G. Karmanova’s sleep evolution theory)

The genetic basis of rest–activity circadian alternation in animal behavior is considered in the evolutionary range from bacteria to mammals. We scrutinize various concepts of sleep development in the animal world evolution as well as the I.G. Karmanova’s theory of the sleep–wake cycle evolution in vertebrates, beginning from wakefulness–primary sleep (or protosleep) in fish and amphibians through wakefulness–intermediate sleep in reptiles to wakefulness–slow wave sleep (SWS) and paradoxical sleep (PS) in birds and mammals. Primary sleep is represented by the three major sleep-like immobility states: catalepsy, catatonia and cataplexy. The main behavioral, somatovegetative and neurophysiological characteristics of primary sleep and the ancient activation pattern during primary sleep are described. The issues of which of these sleep manifestations are homologous to SWS, PS, hibernation and stress response are discussed. In conclusion, the general diagram of sleep evolution in vertebrates is presented, and the I.G. Karmanova’s contribution to evolutionary somnology is highlighted.     

Auditory deprivation modifies biological rhythms in the golden hamster

To assess to what extent auditory sensory deprivation affects biological rhythmicity, sleep/wakefulness cycle and 24 h rhythm in locomotor activity were examined in golden hamsters after bilateral cochlear lesion. An increase in total sleep time as well as a decrease in wakefulness (W) were associated to an augmented number of W episodes, as well as of slow wave sleep (SWS) and paradoxical sleep (PS) episodes in deaf hamsters. The number of episodes of the three behavioural states and the percent duration of W and SWS increased significantly during the light phase of daily photoperiod only. Lower amplitudes of locomotor activity rhythm and a different phase angle as far as light off were found in deaf hamsters kept either under light-dark photoperiod or in constant darkness. Period of locomotor activity remained unchanged after cochlear lesions. The results indicate that auditory deprivation disturbs photic synchronization of rhythms with little effect on the clock timing mechanism itself.     

Behavioral and electrophysiological patterns of wakefulness-sleep states in a lizard.

Four individuals of the lizard Ctenosaura pectinata were chronically implanted for electroencephalographic (EEG), electromyographic (EMG) and electro-oculographic (EOG) recordings. Four different vigilance states were observed throughout the nyctohemeral cycle. These states were: Active wakefulness (Aw), quiet wakefulness (Qw), quiet sleep (Qs) and active sleep (As). Each state displayed its own behavioral and electrophysiological characteristics. EEG waves were similar during Aw and Qw but they diminished in amplitude and frequency when passing from these states to Qs, and both parameters increased during As. Muscular activity was intense in Aw, it decreased during Qw and almost disappeared during Qs. This activity reappeared in a phasic way during As, coinciding with generalized motor manifestations. Ocular activity was intense during Aw but minimal during Qw, it disappeared in Qs and was present intermittently in As. Aw, Qw, Qs and As occupied 5.9%, 25.7%, 67.7% and 0.6% of the 24 hr period, respectively. The frequency and duration of As episodes showed great inter-animal variability and the mean duration was of 12.9 sec. Stimuli reaction threshold was highest during sleep. In conclusion, the lizard Ctenosaura pectinata exhibit two sleep phases (Qs and As) that may be assimilated to slow wave sleep (SWS) and paradoxical sleep (PS) of birds and mammals.     

The role of the posterior hypothalamus in the regulation of paradoxical sleep

Posterior hypothalamus was found to take part in the inhibitory control of the paradoxical sleep executive mechanisms responsible for the ECoG desynchronisation and phasic events. Functional activity of the posterior hypothalamus seems to be at its lowest during the paradoxical sleep stage as characterised by phasic events and the ECoG desynchronisation, and increases during the stage with alpha-like activity in the ECoG and absence of phasic events, the latter having, probably, a "sentinel" function.