Microdialysis and EEG in rats reveal cortical PGE2 changes during sleep and wakefulness

Prostaglandin (PG) E2 production was assessed in freely moving rats using the technique of microdialysis in the prefrontal cortex associated with parallel cortical EEG recordings. PGE2 concentrations were 40% higher during wakefulness than during slow wave sleep. PGE2 values varied during wakefulness with a maximal increase in the middle of the stage and a drop towards lower values before the occurrence of slow wave sleep. These variations were similar to those observed previously in the rostromedial hypothalamus, where PGE2 concentration was 2.6 times lower than that in the cortex. These data document a positive correlation between cortical EEG activation and PGE2 levels. Taken together with pharmacological data on the awakening effect of centrally administered PGE2, these observations are in favor of an involvement of PGE2 in the generation of wakefulness.     

Spectral power and coherence analysis of sleep EEG in AIDS patients: decrease in interhemispheric coherence

Fifteen patients aged between 26 and 55 years with the acquired immunodeficiency syndrome (AIDS) and various cerebral manifestations of the disease underwent an all-night sleep electroencephalogram (EEG) registration. The recordings of 15 age-matched volunteers were examined as controls. Sleep stages were determined visually and the following spectral analysis was based on corresponding artifact-free 40-second periods. The sampling rate was 64 second-1, the spectral resolution was 0.25 Hz and the frequency ranged from 0.25-24 Hz. The power density spectra of eight EEG derivations (left and right frontopolar, frontal, central and occipital; reference montage to the ipsilateral Cb electrodes) and the coherence spectra of interhemispheric (interfrontal, interoccipital) and intrahemispheric (frontooccipital, left and right) channel pairs were computed. The power density of the patients in the 11.5-13-Hz frequency range of nonrapid eye movement (NREM) sleep was considerably lower than that of the controls (p < 0.05 and p < 0.01 at left and right frontal derivations, two-tailed Mann-Whitney U test). The power density of rapid eye movement (REM) sleep showed no consistent differences between the two groups. The interfrontal coherence of the whole frequency range below 12 Hz was markedly lower in the patient group. This applied to NREM sleep and also to REM sleep (p < 0.01 and p < 0.001 for different frequency bands between 1 and 12 Hz in NREM and REM sleep). Possible relations to clinical features are discussed.     

Evening administration of melatonin and bright light: interactions on the EEG during sleep and wakefulness

PROBLEM: Human leukocyte antigen (HLA)-G is uniquely expressed on extravillous cytotrophoblasts of the placenta and is postulated to be a mediator of maternal immune tolerance. Although it was originally considered to be nonpolymorphic, variations of the HLA-G DNA sequence have been reported, and a limited number of HLA-G alleles been defined. METHOD OF STUDY: The HLA-G wild-type sequence was compared with HLA-A2 with regard to the conservation of functionally essential parts of classical HLA-I molecules. HLA-G polymorphisms were analyzed under the aspect of ethnic differences, site, and consequences for postulated molecule functions. RESULTS: HLA-G exhibits a high degree of conservation relative to HLA-A2 in functionally relevant sites of HLA-class I molecules. However, polymorphic sites in HLA-G and classical HLA loci are not congruent. CONCLUSION: The type and localization of HLA-G polymorphisms suggest that different parts of HLA-G molecule underlie different selective constraints.     

The reliability of visual scoring of alpha EEG activity during sleep

The reliability of visual scoring of alpha electroencephalogram activity in nonrapid eye movement sleep was evaluated. Three trained scorers independently, on two occasions, assessed one record from each of 10 patients. In addition to standard sleep staging of the records, alpha activity was scored using three methods: a) while the record was being scored, an assessment of alpha activity during the preceding stage was made at each stage change; b) after the record was scored a single global rating of alpha was made; and c) each 20-second epoch of the record was rated on the amount of alpha present. Relative and absolute generalizability coefficients in excess of 0.810 and 0.698, respectively, were obtained. However, the results also indicated that careful attention to methodological factors is critical in ensuring satisfactory standards of reliability.     

Hemodynamics in sleep-induced apnea. Studies during wakefulness and sleep

Twelve patients with predominantly obstructive type sleep apnea underwent cardiac catheterization, hemodynamic monitoring, and arterial blood gas analysis during wakefulness and sleep. Abnormalities during wakefulness included systemic hypertension in four of 12, exercise-induced mild pulmonary hypertension in five of 12, and alveolar hypoventilation in one. During sleep nine patients had cyclic elevations of arterial pressure with each apneic episode, exceeding 200 mm Hg systolic in three of 12. Pulmonary artery pressures increased in 10 of 12, exceeding 60 mm Hg systolic in five. Marked degrees of hypoxemia (arterial P02, less than 50 mm Hg in eight of 12) and moderate hypercapnia with respiratory acidosis were associated with these hemodynamic changes. Cyclic upper airway obstruction during sleep may result in hypercapnia, acidosis, and pronounced hypoxemia, which can lead to hemodynamic abnormalities during sleep. Sustained pulmonary hypertension and possibly systemic hypertension may follow. Tracheostomy is an effective therapy and is recommended to symptomatic patients who have predominantly obstructive apnea but no relievable anatomic cause of upper airway obstruction.     

Activity of medullary respiratory neurons during ventilator-induced apnea in sleep and wakefulness

Mechanical ventilation of cats in sleep and wakefulness causes apnea, often within two to three cycles of the ventilator. We recorded 137 medullary respiratory neurons in four adult cats during eupnea and during apnea caused by mechanical ventilation. We hypothesized that the residual activity of respiratory neurons during apnea might reveal its cause(s). The results showed that residual activity depended on 1) the amount of nonrespiratory inputs to the cell (cells with more nonrespiratory inputs had greater amounts of residual activity); 2) the cell type (expiratory cells had more residual activity than inspiratory cells); and 3) the state of consciousness (more residual activity in wakefulness and rapid-eye-movement sleep than in non-rapid-eye-movement sleep). None of the cells showed an activation during ventilation that could explain the apnea. Residual activity of approximately one-half of the cells was modulated in phase with the ventilator. The strength of this modulation was quantified by using an effect-size statistic and was found to be weak. The patterns of modulation did not support the idea that mechanoreceptors excite some respiratory cells that, in turn, inhibit others. Indeed, most cells, inspiratory and expiratory, discharged during the deflation-inflation transition of ventilation. Residual activity failed to reveal the cause of apnea but showed that during apnea respiratory neurons act as if they were disinhibited and disfacilitated.     

Effect of strychnine on rat locus coeruleus neurones during sleep and wakefulness

The noradrenergic neurones of the locus coeruleus (LC) discharge tonically during wakefulness, decrease their activity during slow wave sleep and are virtually quiescent during paradoxical sleep. We recently demonstrated an inhibitory glycinergic input to the locus coeruleus and proposed that this could be responsible for inhibition of the LC during paradoxical sleep. To test this proposal, we developed a method combining polygraphic recordings, iontophoresis and single-unit extracellular recordings in the unanaesthetized head-restrained rat. Iontophoretically applied strychnine, a specific glycine antagonist, induced strong excitation of LC neurones during paradoxical sleep, but also during slow wave sleep and wakefulness. These results suggest that glycine tonically inhibits noradrenergic LC neurones throughout the entire sleep-waking cycle and not only during paradoxical sleep.     

Respiratory responses to tracheobronchial stimulation during sleep and wakefulness in the adult cat

The response to tracheal stimulation (50 microliters of tap water) during wakefulness, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep was investigated in adult cats. In wakefulness, repetitive coughing occurred on 80% of the trials. In NREM and REM sleep, the most frequent response (approximately 69% and 58% of the trials, respectively) was arousal, followed by coughing. Apneas occurred following the stimulus and before arousal in 11% and 24% of the trials in NREM and REM sleep, respectively. In NREM sleep, the tracheal stimulus sometimes evoked expiratory efforts following a normal inspiratory effort (11% of the trials). These were much weaker than the expiratory efforts during coughing in wakefulness. In REM sleep, stimulation in 11% of the trials elicited increased inspiratory efforts. Although these may have been diminutive preparatory inspirations for coughing, they were much smaller than preparatory inspirations associated with coughing in wakefulness, and they were never followed by active expiratory efforts. Arousal from either NREM or REM sleep in response to tracheal stimulation was sometimes associated with an augmented breath. This response, which is common upon spontaneous arousal, may lead to deeper aspiration of the tracheal fluid. We conclude that in cats coughing requires wakefulness and that airway stimuli in sleep cause a variety of respiratory responses, some of which may be maladaptive.     

Dynamics of EEG spindle frequency activity during extended sleep in humans: relationship to slow-wave activity and time of day

The dynamics of EEG spindle frequency activity (SFA; spectral power density in the 12.25-15.0 Hz range) and its relationship to slow-wave activity (SWA; 0.75-4.5 Hz) were investigated in long sleep episodes (> 12 h). Young healthy men went to bed at either 19:00 h (early sleep; prior waking 36 h, n = 9) or 24:00 h (late sleep; prior waking 17 h, n = 8). In both nights, SWA in non-rapid-eye-movement sleep (NREMS) decreased over the first three to four 1.5-h intervals and remained at a low level in the subsequent five to six 1.5-h intervals. In contrast, the changes of SFA were more variable and differed between the lower (12.25-13.0 Hz), middle (13.25-14.0 Hz) and higher frequency bin (14.25-15.0 Hz). A pronounced influence of time of day was present in the lower and higher SFA bin, when the dynamics were analyzed with respect to clock time. In both the early and late sleep condition, power density in the lower bin was highest between 2:00 and 5:00 h in the morning and decreased thereafter. In the higher bin, power density was low in the early morning hours and increased as sleep was extended into the daytime hours. The results provide further evidence for a frequency-specific circadian modulation of SFA which becomes more evident at a time when SWA is low.     

Aberrant functional organization in schizophrenia: analysis of EEG coherence during rest and photic stimulation in drug-naive patients

Participation in bronchial asthma pathogenesis of the epithelium, bronchial wall, effector cells of inflammation at various periods of the disease are described. Morphology of the bronchi between the attacks, at the height of the attack and at the experimental model of the bronchospasm is presented. The hypotheses of the bronchospasm and respiratory tract obstruction are discussed.     

Changes in EEG power density during sleep laboratory adaptation

First- and second-night effects on the electroencephalogram (EEG) were investigated by means of polygraphic sleep recordings and all-night spectral analysis. Eighteen normal subjects were studied for three consecutive nights in a hospital sleep laboratory. Visual sleep scoring showed that there was a first-night effect in normal subjects similar to that reported previously [increased wakefulness; decreased total sleep time, sleep efficiency, and rapid eye movement (REM) sleep]. Spectral analysis of the sleep EEG revealed important changes, most of which occurred in REM sleep. Increased delta, theta, and beta1 power densities accompanied by decreased mean frequency were seen in REM sleep in the second night. On the basis of REM sleep deprivation results previously published, our data suggest that the second night could be affected by partial REM sleep deprivation that occurred in the first night. Delta and theta power density values decreased in the first non-rapid eye movement episode of nights 1 and 2; this could result from increased REM sleep pressure. The overall consistency of spectral data in the first and second night with REM sleep findings derived from visual scoring in the first night lends further support to this hypothesis. The sleep disturbance experienced during the first night in a sleep laboratory may be a useful and valid model of transient insomnia. Therefore, we conclude that data from all nights recorded should be included in assessing a subject's sleep.     

The mismatch negativity to frequency deviants during the transition from wakefulness to sleep.

Examined the changes in the mismatch negativity (MMN) during the transition from a waking, conscious state to one of sleep and unconsciousness. Auditory event-related potentials were recorded from 8 Ss, 21–32-yrs old, during the sleep onset period. A 1,000 Hz-standard stimulus was presented every 600 ms. At random, on 20% of the trials, the standard was changed to either a large 2,000-Hz or a small 1,100-Hz deviant. Results indicate that during wakefulness, the large deviant elicited a larger, long-lasting MMN than the small deviant. Following the large deviant during relaxed wakefulness and Stage 2 sleep, the MMN continued to be elicited although it was reduced in amplitude. No significant MMN was recorded for either deviant in Stages 1 and slow wave sleep. The loss of consciousness therefore appears to have a marked effect on the MMN. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic and environmental influences on EEG coherence

EEG coherence measures the covariation in electrical brain activity between two locations on the scalp and is used to study connectivity between cortical regions. The aim of this study was to determine the heritability of EEG coherence. Coherence was measured in a group of 213 16-yr-old twin pairs. By including male and female twin pairs in the sample, sex differences in genetic architecture were systematically examined. The EEG was obtained during quiet supine resting. Coherence was estimated for short and long distance combinations of electrode pairs along the anterior-posterior axis within a hemisphere for four frequency bands (delta, theta, alpha and beta). Averaged over all electrode combinations about 60% of the variance was explained by genetic factors for coherence in the theta, alpha and beta bands. For the delta band, the heritability was somewhat lower. No systematic sex differences in genetic architecture were found. All environmental influences were nonshared, i.e., unique factors including measurement error. Environmental factors shared by twin siblings did not influence variation in EEG coherence. These results suggest that individual differences in coherence form a potential candidate for (molecular) genetic studies on brain function.     

Spindle frequency activity in the sleep EEG: individual differences and topographic distribution

Focal magnetic transcranial stimulation (TCS) is employed for mapping of the motor cortical output to abductor digiti minimi (ADM) muscle. The aim of this study was to evaluate the interhemispheric asymmetries in normals. Motor maps were obtained through motor evoked potentials (MEPs) recordings from ADM muscle in 20 healthy subjects in right and left hemispheres TCS. Measurement of several indexes such as excitability threshold, MEPs amplitude, MEPs latency, and silent period duration did not show differences between the hemispheres. Moreover, no interhemispheric asymmetries were found when the amplitude ratio values were analyzed. The hand motor cortical area, as represented by the number of responsive sites (3.6 vs. 3.5) and the "hot spot" site localization presented a fairly symmetrical organization. Absolute values displayed a relatively wide intersubject variability, while their interhemispheric differences were extremely restricted. This observation can offer a new tool in diagnosing and following up neurological disorders affecting the central motor system, mainly for those concerning monohemispheric lesions.     

Disturbances of wakefulness, sleep and respiratory function in Steinert's disease

36 night sleep recordings were carried out on 15 patients suffering from myotonia dystrophica. 9 of these patients complained of diurnal hypersomnia. 10 patients had a disturbance of night sleep with a reduction of REM sleep sometimes associated with interruption of the recording with an increase in the light stages of sleep or alternatively with an increase of REM sleep with a reduction in the latency period of the first paradoxical sleep or with narcoleptic elements. 13 patients had abnormally early abolition of chin EMG activity, almost on falling asleep. 11 cases had pathological apnoeic episodes during sleep and in 9 of the 10 patients who underwent respiratory function studies there was a restrictive airways defect. In addition 9 had frank hypoxia without hypercapnia and 4 a right to left shunt. 3 clinically unaffected patients but with affected relatives were also investigated, 2 were found to have sleep disturbances 1 of which was associated with early abolition of tone.     

Abnormal functional connectivity in Alzheimer''s disease: intrahemispheric EEG coherence during rest and photic stimulation

Tolbutamide is a sulfonylurea oral hypoglycaemic agent with suspected teratogenicity in humans and demonstrated teratogenicity in laboratory animals, but the underlying mechanism is unknown. This study examined maternal-to-conceptus tolbutamide transfer on gestational days 9.5 and 10.5 and drug concentration in embryonic head, heart, and trunk regions on gestational day 10.5 after maternal dosing in mouse. Embryos exposed to tolbutamide in vitro on gestational day 8.5 were assayed for glucose uptake, glycolysis, and protein content after 6, 12, and 24 hr. Dose-dependent tolbutamide transfer from maternal serum to extraembryonic fluid occurred on gestational day 9.5 and 10.5, with highest tolbutamide levels in embryonic heart on gestational day 10.5. In vitro tolbutamide exposure on gestational day 8.5 decreased glycolysis at 6 hr, increased glycolysis at 24 hr, and had no effect on glucose uptake at 6, 12, or 24 hr. Embryonic protein content reflected growth retardation after 24 hr tolbutamide exposure. Thus, mouse embryos are directly exposed to tolbutamide after maternal dosing on gestational day 9.5 and 10.5, with concentration of drug within embryonic heart. Tolbutamide-induced changes in glucose metabolism are less apparent in whole embryos than reported in adult tissues.     

Colonic motor activity in women during sleep

Regulators of G-protein signalling (RGS) are recently identified proteins that shorten the lifetime of the activated G protein. We now show that rat cardiac myocytes express mRNA for at least 10 RGS. The mRNA for RGS-r is barely detectable in rat ventricles, but increases more than 20-fold during the 60- to 90-min process of isolating ventricular myocytes, and after 90 min of culture of atrial pieces in medium with Ca2+. Both in myocytes and in atria, the rise in RGS-r is transient. The mRNA for cardiac RGS5, but not RGS-r, is developmentally regulated. These studies suggest that rapid regulation of RGS levels may be a new mechanism that governs how signals are transmitted across the cardiac cell membrane.     

Regional changes in EEG power and coherence during cognition: Intensive study of two individuals.

Studied whether EEG power is relevant to cognitive performance by conducting weekly EEG recordings on 2 adult male volunteers who were living for several months in a controlled laboratory environment. Data from an 8-channel EEG during a resting period and during performance of 2 cognitive tasks (word fluency and mental imagery) were subjected to spectral analysis. Statistical analyses on power and coherence were conducted for each S separately. Although substantial individual differences were observed, particularly for the theta band, both Ss showed changes in the spectral information over the anterior left hemisphere during the word fluency task. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)