Effects of bilateral dorsolateral pontine tegmentum lesions on hippocampus theta rhythm during paradoxical sleep in the rat]

Electrolytic lesions of the dorsolateral pontine tegmentum aimed at the locus coeruleus (LC) were performed bilaterally in 13 chronically implanted Rats. Following lesions, transient alterations of characteristic components of theta rhythm appeared. No shortening of duration of paradoxical sleep (PS) was observed. These results do not support the hypothesis that neurons of LC are directly involved in the production of theta rhythm during PS; moreover they seem not to be necessary to the normal appearance of this state of sleep.     

Ontogenetic analysis of the theta rhythm during paradoxical sleep in rats]

In the rat, an ontogenetic study of theta rhythm during paradoxical sleep shows a clear evolution between the 14th and the 30th postnatal day. During this period, its mean frequency increases from 5 to 7 cycles per second, and its spectrum shows significant changes. These parameters (mean frequency and spectral components) of the theta rhythm could be a useful index of brain maturation in the rat.     

Human slow wave sleep: A review and appraisal of recent findings,with implications for sleep functions,and psychiatric illness

Recent findings concerning human slow wave sleep (hSWS-stages 3+4; delta EEG activity) are critically reviewed. Areas covered include the significance of the first hSWS cycle; hSWS in extended sleep; relationship between hSWS, prior wakefulness and sleep loss; hSWS influence on sleep length; problems with hSWS deprivation; influence of the circadian rhythm; individual differences in hSWS, especially, age, gender and constitutional variables such as physical fitness and body composition. Transient increases in hSWS can be produced by increasing both the quality and quantity of prior wakefulness, with an underlying mechanism perhaps relating to the waking level of brain metabolism. Whilst there may also be thermoregulatory influences on hSWS, hypotheses that energy conservation and brain cooling are major roles for hSWS are debatable. hSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated. The hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link.     

Human slow wave sleep: a review and appraisal of recent findings, with implications for sleep functions, and psychiatric illness.

Recent findings concerning human slow wave sleep (hSWS-stages 3 + 4; delta EEG activity) are critically reviewed. Areas covered include the significance of the first hSWS cycle; hSWS in extended sleep; relationship between hSWS, prior wakefulness and sleep loss; hSWS influence on sleep length; problems with hSWS deprivation; influence of the circadian rhythm; individual differences in hSWS, especially, age, gender and constitutional variables such as physical fitness and body composition. Transient increases in hSWS can be produced by increasing both the quality and quantity of prior wakefulness, with an underlying mechanism perhaps relating to the waking level of brain metabolism. Whilst there may also be thermoregulatory influences on hSWS, hypotheses that energy conservation and brain cooling are major roles for hSWS are debatable. hSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated. The hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link.     

Circabidian rhythm: its appearance and disappearance in association with a bright light pulse

A shift from circadian to circabidian periods or vice versa was observed in the rhythm of sleep and wakefulness under temporal isolation. The shift occurred in two subjects, 3 times in association with a single bright light pulse applied, 4 times in all. The finding suggests that the bright light pulse has an additional effect to the phase shift on the human circadian system.     

Phasic hippocampal activity during paradoxical sleep in the rat: selective suppression after diazepam administration

Summary The effects of diazepam on tonic (T) and phasic (P) components of the paradoxical-sleep hippocampal theta rhythm were studied in the rat. Results show that diazepam, a benzodiazepine analogue known to interfere with the putative neurotransmitter -aminobutyric acid (GABA) in the mammalian central nervous system, selectively abolishes P. They confirm previous data according to which sedative/anaesthetic drugs cause, an apparent dissociation of T and P of the paradoxical-sleep hippocampal theta rhythm. Moreover, they suggest a possible involvement of GABA in the neurochemical mechanisms underlying P in the rat.     

Sleep in the tortoiseKinosternon sp.

Summary Individuals ofKinosternon sp., previously confined to laboratory conditions, were chronically implanted with electrodes for electroencephalogram, electro-oculogram and electrocardiogram recording. Behavioral states of waking and sleep were clearly observed. Two sleep stages were present: quiet sleep and REM or active sleep. Electrical cerebral activity was polymorphic and irregular. EEG frequencies declined and amplitudes diminished with sleep. Arrhythmic spikes occurred during behavioral sleep and declined with waking. Heart rate decreased when passing from wakefulness to quiet sleep. It was slightly but consistently higher during active sleep compared with quiet sleep.     

Insomnia induced by P-chlorophenylalanine in cats. Its reversibility by intraventricular injections of indolamines

Intraventricular injection of 250 microgram of 5 HTP induces both slow wave and paradoxical sleep, after 20-60 min. latencies, in insomniac Cats pretreated with P-chlorophenylalanine. Direct injections of 5 HTP in several brain stem structures do not induce sleep. The long latency or paradoxical sleep induction and its suppression with chloramphenicol suggest that indolamines are not directly responsible for paradoxical sleep, but that they act by controlling the synthesis and/or the liberation in the periventricular system of some specific paradoxical sleep inducing factor.     

Electrophysiological semeiology of sleep

Summary The main characteristics of electroencephalograms, electro-oculograms and electromyograms in human sleep are described. This electrophysiological semeiology permits the identification of the different stages in normal sleep. In animals, sleep is generally less differentiated; the possibility of recording subcortical structures allows the observation of additional phenomena such as hippocampal theta, activity and PGO spikes. Evoked brain electrical activity is less well known than the spontaneous activity in sleep. Recent technological developments offer many interesting possibilities in the processing of the EEG and other physiological signals.     

EEG and sleep in aged hospitalized patients with senile dementia: 24-h recordings

Polygraphic recordings of wake and sleep were performed on 10 partly bed-ridden, severely deteriorated patients with senile dementia. Compared with healthy elderly persons these subjects showed less SWS (slow wave sleep, characterized by high amplitude, slow EEG waves), less REM sleep (rapid eye movement sleep, usually accompanied by dream activity) and poorly organized stage 2 sleep (no sleep spindles, i.e. phasic EEG activity with a frequency of 12-14 Hz). Six of the 10 patients had no dominant alpha rhythm during wakefulness; this seemed to be related to their more deteriorated clinical state, to still less SWS and REM sleep and more time spent in stage 2. The basic NREM-REM cycle of sleep, i.e. the regular alternation between non-REM- and REM-periods, could still be distinguished, however, and showed similar average temporal characteristics as in healthy old and younger people. Similarly, although sleep was severely fragmented in most patients and many sleep episodes occurred during the day, the day-night alternation of wakefulness and sleep was maintained in the sample as a whole.     

Intrathalamic sensory connections mediated by the thalamic reticular nucleus

The thalamus and cerebral cortex are linked together to form a vast network of interconnections. Different modes of interactions among the cells in this network underlie different states of consciousness, such as wakefulness and sleep. Interposed between the dorsal thalamus and cortex are the GABAergic neurons of the thalamic reticular nucleus (TRN), which play a pivotal role not only in switching between the awake and sleep states but also in sensory processing during the awake state. The visual, somatosensory, and auditory sectors of TRN share many of the same organizational features. Each of these sectors contains maps, which are related to its inputs and outputs, and organizational components called ‘slabs.’ It is proposed that, during wakefulness, TRN is crucially involved in resetting the activity levels in sensory nuclei of the dorsal thalamus, which allows the cortex to actively and periodically compare its on-going sensory processing with the available sensory information. Received 11 May 1999; received after revision 15 July 1999; accepted 21 July 1999     

Sleep in an Amazonian manatee, Trichechus inunguis.

For the first time, sleep was studied in a representative of the order of Sirenia. Slow wave sleep occupied 27%, and paradoxical sleep 1% of the total recording time in the Amazonian manatee. Trichechus inunguis. The circadian rhythmicity of sleep was pronounced. During the sleep period, the manatee woke up for a short time for each respiratory act. Interhemispheric asynchrony of the electrocortical slow wave activity was found.     

Sleep in an Amazonian manatee,Trichechus inunguis

For the first time, sleep was studied in a representative of the order of Sirenia. Slow wave sleep occupied 27%, and paradoxical sleep 1% of the total recording time in the Amazonian manatee,Trichechus inunguis. The circadian rhythmicity of sleep was pronounced. During the sleep period, the manatee woke up for a short time for each respiratory act. Interhemispheric asynchrony of the electrocortical slow wave activity was found.     

Splitting of the circadian activity rhythm in common marmosets (Callithrix j. jacchus; primates)

Long-term recordings of the free-running circadian activity rhythm in common marmosets, Callithrix j. jacchus, living under constant environmental conditions (LL 200-470 lx) provided evidence of rhythm splitting in nonhuman primates. In two out of ten test animals two different types of splitting occurred; spontaneous persistent splitting and temporary splitting. Neither a reduction of the illumination intensity nor the application of dark pulses had any effect on the two activity components of the persistently split rhythm.     

Different action of alpha-methyl-DOPA on sleep and labyrinth learning in 2 inbred strains of mice]

In two inbred mice strains C 57 BR and C 57 BL/6 presenting the same type of sleep, but a different capacity of learning, Alpha-Methyl-Dopa (100 mg/kg) injected after every session, suppresses paradoxical sleep completely for 9 to 11 h. Maze-learning performance is retarded in C 57 BR mice, but facilitated in C 57 BL/6.     

Long-term motor activity recording of dogs and the effect of sleep deprivation

Summary Motor activity of laboratory dogs was recorded for several weeks with an ambulatory monitoring device. The effect of 24 h sleep deprivation (SD) on motor activity during recovery was investigated. A clear rest-activity rhythm was established. The dogs exhibited a similar mean daily rest-activity pattern: 1) rest occurred mainly in the dark; 2) the amimals were most active after light onset; activity increased during the last two dark hours; 3) a rest period was found at noon and reduced activity during afternoon hours. There was a marked difference in total activity between individual dogs. Activity patterns varied as a function of the day of the week; this may have been a reflection of variations in the level of human activities in the laboratory. There was a significant reduction of motor activity during the 24-h period following SD. This was particularly evident in the first 6 h of the light period immediately following the deprivation.In addition, there was a significant increase in the number of episodes with activity 5 counts during recovery. The study confirms the possibility of measuring motor activity to assess compensatory mechanisms during recovery after SD. Sleep regulation, therefore, does not necessarily need to be exclusively examined by the invasive technique of EEG registration.     

Statistical relationship between "slow-wave sleep" and "paradoxical sleep" in rats]

In the Rat, statistical analysis of slow sleep (SS) and paradoxical sleep (PS) episodes disclosed two significant (p less than 0,01) positive correlations: (1) Over a four-hour period, the mean duration of PS episodes was correlated to the mean of the just preceding "light" SS episodes; (2) On the contrary, from cycle to cycle of sleep-wakefulness, the duration of each PS episode was correlated to that of the "light" SS episode of the next cycle.     

Interdependence between locomotor activity and duration of wakefulness in humans during isolation

Locomotor activity was recorded in 14 subjects who lived singly in an isolation unit for 16 to 88 days. Their free-running circadian rhythms had a mean period of 25.9 h, with individual means in the duration of wakefulness (alpha) ranging from 12.1 to 22.9 h. Intraindividually, the hourly means of activity were negatively correlated with alpha to such a degree that the total amount of activity per 'day' remained constant irrespective of large variations in alpha.     

Rhythms of enzymatic activity in maternal and umbilical cord blood

The 24-h activity patterns of variouns enzymes were determined in human serum, red blood cells and white blood cells of maternal and umbilical cord blood. Blood was drawn from the brachial vein of mothers and from the umbilical cord within ten minutes after delivery. Corresponding blood specimens were obtained from 83 spontaneous labors, occurring at different hours over a period of 60 days. For each variable (variable=activity of a specific enzyme in one of the blood components) the results were grouped according to delivery hour, forming a 24-h pattern which was analyzed to elucidate time dependency. Five out of six corresponding maternal and fetal variables were similar with regard to pattern and peak time. The activity rhythms of glyceraldehyde-3-phosphate dehydrogenase and glucose phosphate isomerase in red blood cells of mothers and fetuses possessed a significant bimodal pattern. The activity rhythms of the latter enzyme in white blood cells and sera exhibited a significant 24-h period. Hexosaminidase activity exhibited a distinct 24-h rhythm in maternal white blood cells, but no significant rhythm could be detected in the fetal white blood cells. The activity of hexosaminidase showed, identical 24-h patterns in maternal and cord serum when analyzed by best fit cosine, and no significant time-dependency when analyzed by ANOVA.     

Single injections of triazolam,a short-acting benzodiazepine,lengthen the period of the circadian activity rhythm in golden hamsters

Single injections of the benzodiazepine, triazolam, induce phase shifts and cause a lengthening of the circadian activity rhythm in the golden hamster. The effect of triazolam on period depends on the phase of injection, but is not dependent on the direction of the phase shifts. Triazolam injections caused increases in period that were associated with phase advances as well as phase delays in the activity rhythm. This relationship between triazolam-induced phase shifts and changes in period is different from the relationship between light-induced phase shifts and period changes.