Short-term sleep fragmentation enhances anxiety-related behavior: The role of hormonal alterations.

INTRODUCTION: The neuroendocrine background of acute sleep fragmentation in obstructive sleep apnea and sleep fragmentation involvement in psychiatric comorbidities, common in these patients, are still largely unknown. The aim of this study was to determine the effects of short-term experimental sleep fragmentation on anxiety -like behavior and hormonal status in rats. METHODS: Male rats were adapted to treadmill (ON and OFF mode with belt speed set on 0.02m/s and 0.00m/s) and randomized to: 1) treadmill control (TC, only OFF mode); 2) motion, activity control (AC, 10min ON and 30min OFF mode) and 3) sleep fragmentation (SF, 30s ON and 90s OFF mode) group. Six hours later, the animals were tested in the open field, elevated plus maze and light/dark test (n = 8/group). Testosterone, estradiol, progesterone and corticosterone were determined in separate animal cohort immediately upon sleep fragmentation (n = 6/group). RESULTS: SF rats showed decreased rearings number, decreased time spent in the central area and increased thigmotaxic index compared to TC and AC rats in the open field test. Similarly, increased anxiety upon sleep fragmentation was observed in the elevated plus maze and the light/dark test. Significantly lower testosterone, estradiol and progesterone levels were determined in SF in comparison to AC and TC groups, while there was no significant difference in the levels of corticosterone. CONCLUSION: Short term sleep fragmentation enhances anxiety-related behavior in rats, which could be partly mediated by the observed hormonal changes presented in the current study in form of testosterone, estradiol and progesterone depletion.

Hypocretin measurement: shelf age of radioimmunoassay kit, but not freezer time, influences assay variability.

The hypothalamic peptide hypocretin 1 (orexin A) may be assayed in cerebrospinal fluid to diagnose narcolepsy type 1. This testing is not commercially available, and factors contributing to assay variability have not previously been comprehensively explored. In the present study, cerebrospinal fluid hypocretin concentrations were determined in duplicate in 155 patient samples, across a range of sleep disorders. Intra-assay variability of these measures was analyzed. Inter-assay correlation between samples tested at Emory and at Stanford was high (r = 0.79, p < 0.0001). Intra-assay correlation between samples tested in duplicate in our center was also high (r = 0.88, p < 0.0001); intra-assay variability, expressed as the difference between values as a percentage of the higher value, was low at 9.4% (SD = 7.9%). Although both time the sample spent in the freezer (r = 0.16, p = 0.04) and age of the kit used for assay (t = 3.64, p = 0.0004) were significant predictors of intra-kit variability in univariate analyses, only age of kit was significant in multivariate linear regression (F = 4.93, p = 0.03). Age of radioimmunoassay kit affects intra-kit variability of measured hypocretin values, such that kits closer to expiration exhibit significantly more variability.

Role of chemoreception in cardiorespiratory acclimatization to, and deacclimatization from, hypoxia.

During sojourn to high altitudes, progressive time-dependent increases occur in ventilation and in sympathetic nerve activity over several days, and these increases persist upon acute restoration of normoxia. We discuss evidence concerning potential mediators of these changes, including the following: 1) correction of alkalinity in cerebrospinal fluid; 2) increased sensitivity of carotid chemoreceptors; and 3) augmented translation of carotid chemoreceptor input (at the level of the central nervous system) into increased respiratory motor output via sensitization of hypoxic sensitive neurons in the central nervous system and/or an interdependence of central chemoreceptor responsiveness on peripheral chemoreceptor sensory input. The pros and cons of chemoreceptor sensitization and cardiorespiratory acclimatization to hypoxia and intermittent hypoxemia are also discussed in terms of their influences on arterial oxygenation, the work of breathing, sympathoexcitation, systemic blood pressure, and exercise performance. We propose that these adaptive processes may have negative implications for the cardiovascular health of patients with sleep apnea and perhaps even for athletes undergoing regimens of "sleep high-train low"!

Cerebrospinal fluid histamine levels are decreased in patients with narcolepsy and excessive daytime sleepiness of other origin.

Histaminergic neurons of the hypothalamic tuberomammillary nucleus constitute a major wake-promoting system. In animals, cerebrospinal fluid (CSF) histamine levels are increased during wakefulness and after sleep deprivation and decreased during sleep. An involvement of the histamine system in human disorders has not, to our knowledge, been reported. We measured hypocretin-1 and histamine levels in the lumbar CSF of 28 patients with and without excessive daytime sleepiness (EDS) as assessed by the Epworth Sleepiness Scale (ESS). There were 10 patients with EDS (ESS > 10, mean ESS = 14). Diagnoses included narcolepsy (n = 4), idiopathic hypersomnia (n = 2), sleep apnoea (n = 2) and multiple sclerosis (n = 2). Three patients were treated with stimulants. Their mean CSF histamine was 258 ± 159 PM. There were 18 patients without EDS (ESS < 9, mean ESS = 5). No patients were treated with stimulants. Their mean CSF histamine was significantly higher (624 ± 481 PM, P = 0.007). There was a significant inverse correlation (r = -0.48, P = 0.02) between ESS and both CSF histamine and hypocretin-1 levels. These observations suggest that narcolepsy and EDS of other origin are associated in humans with lower CSF histamine levels and therefore with a reduced activity of the wake-promoting histaminergic neuronal system.

[Myasthenia gravis and sleep]. / Myasthenia gravis und Schlaf.

In myasthenia gravis respiratory function is often disturbed in the night, especially during REM sleep, despite of normal daytime respiratory function. Nevertheless, nocturnal respiratory problems are rarely diagnosed. Sleepiness, concentration and memory problems can be symptoms of a sleep related breathing disorder. Reports of reduction of REM sleep, memory dysfunction, and detection of acetylcholine receptor (AchR)-antibodies in the cerebrospinal fluid have lead to the hypothesis of a central nervous system involvement in myasthenia gravis. Possible mechanisms are centrally acting AchR-antibodies, unspecifically acting cytokines and hypoxia, possibly the most important influence upon REM sleep reduction and impaired cognitive function. In a patient presenting possible CNS-involvement (cephalea, fatigue, concentration and memory problems), a polysomnographic investigation should therefore be performed to detect a sleep related breathing disorder.

Changes in serotonin metabolism may elicit obstructive apnoea in the newborn rat.

1. Experiments were performed on anaesthetized newborn rats (aged 3-10 days) to know whether an increase in central serotonin levels might favour the occurrence of obstructive apnoeas as previously suggested by in vitro results from our group. 2. The levels of serotonin (5-HT), its precursor 5-hydroxytryptophan (5-HTP) and its metabolite, 5-hydroxyindole-acetic acid (5-HIAA), were analysed in cerebrospinal fluid samples collected at the level of the obex prior to and after intraperitoneal injection of L-tryptophan (50 mg kg-1) in sixty-eight anaesthetized newborn rats (control rats prior to injection and injected rats 15, 30 and 45 min after the injection). A significant increase in 5-HT and 5-HTP levels occurred 30 min after the injection, attesting to the activation of 5-HT biosynthesis. 3. The EMG activity of both the genioglossus and the diaphragm was recorded before and after L-tryptophan load (50 mg kg-1) in twenty-two newborn rats. After the injection of L-tryptophan, the amplitude of the integrated genioglossus activity decreased, or was even abolished, either during a few respiratory cycles or for long periods in twenty-one out of twenty-two animals. Recovery of the genioglossus activity occurred within 45-60 min. 4. The thoracic respiratory movements and the resulting upper airway pressure changes were recorded before and after L-tryptophan injection (50 mg kg-1) in sixty-two animals. In some litters (n = 7), most of the animals (21/25) displayed, within 20-40 min of the injection, recurrent episodes of obstructive apnoea often followed by central ones. These respiratory difficulties became severe and drastic, and led in two instances to respiratory distress and death. Lower doses of L-tryptophan (10 mg kg-1) did not induce any respiratory disorders unless these were potentiated by pargyline treatment (50 mg kg-1, n = 7). The obstructive apnoeas liable to occur after an L-tryptophan load (50 mg kg-1) were prevented by blocking the 5-HT receptor with methysergide (50 mg kg-1, n = 5) or by blocking the 5-HT biosynthesis by applying p-chlorophenylalanine (PCPA) pretreatment at birth (300 mg kg-1, n = 7). In other litters (n = 6), none of the eighteen newborn rats tested were affected by L-tryptophan, however, In five young adult rats, L-tryptophan again had no effect.4+ e

Substance P, thyrotropin-releasing hormone, and monoamine metabolites in cerebrospinal fluid in sleep apnea patients.

The cerebrospinal fluid (CSF) concentrations of thyrotropin-releasing hormone (TRH), substance P (SP), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenyl glycol (MHPG) were measured in 15 consecutive patients with the sleep apnea syndrome (SAS) and in healthy control subjects. Second measurements were performed 6 months after surgical treatment in 10 of the patients. The mean (+/- SD) concentration of TRH-like immunoreactive material (TRH-LIM) (pg/ml) did not differ significantly between patients with SAS (8.1 +/- 2.8) and control subjects (7.5 +/- 2.2). However, postoperatively, this concentration was increased in the six clinically cured patients with SAS, from 6.9 +/- 2.7 to 9.4 +/- 1.6 (p less than 0.03). Substance P-like immunoreactive material (SP-LIM) was higher in untreated patients with SAS than in control subjects: 19.2 +/- 6.7 versus 14.4 +/- 4.2 fmol/ml (p less than 0.02), and the level remained high after operation in the group treated surgically. The HVA, 5-HIAA, and MHPG concentrations were similar in patients with SAS and control subjects, and no consistent changes were found postoperatively. The CSF deviations in TRH-LIM and SP-LIM concentrations in the patients may reflect a primary central nervous system defect or they may be secondary to intermittent nocturnal hypoxia, progressive hypercapnia, and/or sleep fragmentation. In this sense, both these systems may be markers of SAS-SP as a "trait" marker and TRH as an indicator of the current state.

Naltrexone therapy of apnea in children with elevated cerebrospinal fluid beta-endorphin.

Previous studies have indicated increased immunoreactivity of the endogenous opioid peptide beta-endorphin in the cerebrospinal fluid (CSF) of infants under 2 years of age with apnea. To assess the role of endogenous opioids in the pathogenesis of apnea in children, the effect of oral treatment with the opioid antagonist naltrexone was studied in apneic infants, as well as in older apneic children, with demonstrated increases in CSF immunoreactive beta-endorphin (i-BE). In the 8 apneic infants with elevated i-BE in lumbar CSF (range, 55-155 pg/ml; normal, 17-52 pg/ml), no further apnea occurred during naltrexone therapy (1 mg/kg/day, by mouth). Five children (2-8 years old) with apnea of unknown cause had elevated CSF i-BE (range, 74-276 pg/ml) compared to 6 age-matched nonapneic children (range, 15-48 pg/ml). No apneic events occurred during naltrexone therapy, except in 1 child during stressful events, but apnea recurred in some patients after attempts to discontinue naltrexone treatment. Adverse effects of naltrexone included complaints of headaches in 2 children and symptoms of a narcotic withdrawal syndrome during the first 3 days of treatment in 1 child. Three children with Leigh's syndrome had elevated CSF i-BE (range, 104-291 pg/ml) and their apnea also responded to naltrexone. We conclude that elevated endogenous opioids contribute to the pathogenesis of apnea in children and may even result in physical dependence.

Increased CSF opioid activity in sleep apnea syndrome. Regression after successful treatment.

The etiology of the SAS is unknown. To test whether endogenous opioids could be pathologically active in SAS, markers of opioid systems were measured in the CSF of 15 patients with SAS and in control subjects. Measured by receptor assay, the concentration of so-called fraction 1 opioid was higher in patients with SAS (3.0 +/- 1.5 pmol/ml; mean +/- SD) than in control subjects (1.1 +/- 0.5 pmol/ml) (p less than 0.01), whereas that of fraction 2 opioid was similar in the two groups. Beta-endorphin-like activity, measured by radioimmunoassay, was somewhat lower in patients with SAS (14.0 +/- 2.8 pmol/ml) than in control subjects (21.8 +/- 7.6 pmol/ml) (p less than 0.05). Six months after surgical treatment of the soft palate, new measurements were made in eight patients. Fraction 2 endorphin and beta-endorphin showed no consistent changes. A decrease in the level of fraction 1 from 4.1 +/- 1.5 pmol/ml to 2.3 +/- 1.0 pmol/ml (p less than 0.02) was noted in those six patients showing a successful clinical course. The data support the hypothesis that in SAS the opioid activity is increased.

Changes in cerebrospinal fluid homovanillic acid in children with Ondine's curse.

The cerebrospinal fluid (CSF) concentrations of three acid monoamine metabolites, two purines, and a group of amino acids were determined in two children with chronic central alveolar hypoventilation (Ondine's curse). The levels of all assayed neuroactive substances, metabolites, and amino acids, with one exception, were normal compared to an age-matched group of neurologically healthy children. The levels of the dopamine metabolite homovanillic acid in the children with Ondine's curse were approximately 2.4 times higher than expected for age range. The present findings may indicate a link between central nervous system dopamine activity and chronic central alveolar hypoventilation. Among other possible explanations, the changes seen might represent a primary alteration in dopamine activity or may reflect a change in dopamine turnover resulting from the chronic hypoventilation.

Cerebrospinal fluid adenosine 3',5'-monophosphate, 5-hydroxyindoleacetic acid and homovanillic acid in patients with sleep apnoea syndrome.

Adenosine 3',5'-monophosphate (cyclic AMP), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were determined in the cerebrospinal fluid of patients with respiratory disorder and hypersomnia and in control patients. Patients with the sleep apnoea syndrome confirmed polygraphically showed elevated levels of cyclic AMP and 5-HIAA. Cyclic AMP levels were inversely correlated with arterial Po(2), measured under resting conditions. The level of HVA also was raised, but the change was not statistically significant.