BACKGROUND: Paradoxical sleep deprivation (PSD) is known for its antidepressive property, both in humans and experimental animals. The small platform method used to promote PSD in rats, however, involves stress similar to that observed in the methods used to induce depressive-like state.
OBJECTIVE AND METHODS: As sucrose solution intake is validated as a depressive-state marker in the rat, the present study evaluated such parameter before, during and after PSD carried out by the small platform method.
RESULTS: The daily mean sucrose solution (15%) ingested by a group of 11 adult male Wistar rats was progressively reduced with PSD. The daily fall in sucrose intake was statistically significant (t-test, p<0.05) from baseline, except in the second day of PSD. The development of taste aversion does not explain the reduction in sucrose intake, since its consumption, 2 days after the end of 4 days of PSD (n=5), was similar to baseline levels. PSD until the animals ceased to stay on the platform (n=6) showed to promote deaths in the recovery period with low consumption of sucrose.
CONCLUSION: The relationship of the data obtained with the development of anhedonia and carbohidrate metabolism opens new interesting aspects for investigation.
Keywords: sleep deprivation, method, stress, rats, sucrose intake, anhedonia.
BACKGROUND: Literature findings have suggested that brain morphological changes may underlie behavioral disturbances such as depression. In depressed patients, alteration in the volume of some brain regions were described and in laboratory animals antidepressant treatments change neuronal nuclei volume and axon densities in some brain regions. Rapid eye movement (REM) sleep deprivation has antidepressant effect in humans and in animals models of depression; moreover it induces changes in brain neurotransmission similar to those obtained after chronic antidepressant drug treatment (i.e., down-regulation of beta-adrenergic receptors and decreased synthesis of noradrenaline-stimulated cAMP).
OBJECTIVE AND METHODS: The aim of this work was to determine if REM sleep deprivation would induce morphological changes in the brains of rats. The effects of REM sleep deprivation on the nuclear volume of neurons from the locus coeruleus, the main noradrenergic nucleus in the brain, hippocampus (area CA1) and cingulate cortex, two brain areas innervated by locus coeruleus, were studied.
RESULTS: The results obtained showed that REM sleep deprivation significantly decreased the nuclear volume of neurons in the locus coeruleus and in cingulate cortex and hippocampus, whereas stress significantly decreased the mean nuclear volume of neurons only from the hippocampus.
CONCLUSION: A change in cell nuclear volume suggests a change in its metabolic activity, therefore, our data provide an anatomical basis for further studies of neuron's morphology in brain structures after REM sleep deprivation.
Keywords: REM sleep deprivation, locus coeruleus, hippocampus, cingulate cortex, neuron nuclear volume, neuronal morphology.
BACKGROUND AND OBJECTIVES: Stress has been implicated in the pathogenesis of several diseases. In this study, we evaluated the effects of different chronic modalities of stress, namely paradoxical sleep deprivation (PSD), electrical footshock (FS), forced swim (SW), and restraint (R), on blood parameters associated with cardiovascular risk in adult male rats.
METHODS: FS and SW were applied twice per day for periods of one hour at 09:00 and 16:00h. Restrained animals were maintained in plastic cylinders for 22 h/day, whereas PSD was continuous. Rats were submitted to all stress modalities for four consecutive days.
RESULTS: Our results demonstrated that PSD induced a significant increase in high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol concentrations and led to a reduction in the levels of triglycerides and very low-density lipoprotein (VLDL) cholesterol. SW and R groups showed a decrease in total cholesterol and HDL cholesterol fractions, and FS increased LDL cholesterol concentrations. The PSD group displayed the highest concentrations of HDL and LDL compared to other groups (SW and R).
CONCLUSION: These results suggest that each type of stress produces distinct effects on lipid metabolism.
Keywords: Sleep deprivation, stress, cholesterol, triglycerides, LDL, corticosterone, cardiovascular risk.
BACKGROUND: The past decades have seen the conduction of a great number of studies that have attempted to assess the effects of physical exercise on sleep. However, the majority of these studies have specifically evaluated the effects of aerobic exercise. To the best of our knowledge, only one study has evaluated the effects of resistance exercise (RE) on sleep patterns.
OBJECTIVE: The aim of the current investigation is to verify the effect of one session of RE on the sleep patterns of sedentary individuals with good sleep quality.
METHODS: Twenty-seven sedentary men with good sleep quality between the ages of 20 and 40 participated in this investigation. The experimental protocol consisted of one session of RE, which was comprised of 3 sets of 15 repetitions with a load equivalent to 50% of the one-repetition maximum test (1-RM) with 90 sec intervals between each set. The sleep parameters were analyzed by means of a t-test, with significance defined as p < 0.05.
RESULTS: No significant differences were found between sleep parameters when RE was performed during different periods of the day. However, the sleep onset latency and the sleep efficiency in the evening group showed a trend toward alteration (p = 0.06).
CONCLUSION: Sedentary individuals with good sleep quality did not display significant alterations in their sleep parameters after performing one session of RE with a load equivalent to 50% of 1-RM.
Keywords: physical exercise, physical activity, slow-wave sleep, REM sleep, polysomnography.
BACKGROUND AND OBJECTIVE: Insomnia, the most frequent sleep disorder, significantly affects quality of life. The purpose of this study was to determine the prevalence of insomnia in the general population of adults in the State of Mato Grosso do Sul, Brazil.
METHODS: A representative random sample of the population of 77 counties in the State of Mato Grosso do Sul (n = 569) was stratified by gender, age and socioeconomic status. Insomnia was classified as difficulty in initiating sleep, difficulty in maintaining sleep or early morning awakening. A structured questionnaire was used to collect data after informed consent from participants. Statistical analysis was conducted using the chi-square and Fisher's exact tests, and inferences based on the binomial prevalence of insomnia.
RESULTS: Prevalence of insomnia was 19.93% in the study population, 25.17% among women and 14.86% among men. The mean age of the participants was 40.69 ± 14.18. The prevalence of insomnia was higher among separated people (31.11%). Hypnotic drugs were used by 7.90% of the participants and by 43.48% of those with insomnia in the preceding month.
CONCLUSION: The State of Mato Grosso do Sul, Brazil, has high prevalence rates of insomnia and the use of hypnotic drugs among the general population, despite the good predictors of quality of life and socioeconomic growth.
Keywords: insomnia, sleep disorders, hypnotic drugs, cross-sectional study, Mato Grosso do Sul, Brazil.
The role of stress as a triggering factor for insomnia is widely accepted. However, not everybody who is submitted to a stressful event develops insomnia, which indicates that it depends on individual vulnerability. In addition, the neurobiology of vulnerable individuals is far from known. Animal models are valuable instruments to disclose mechanisms involved in the installation of the disease, not to mention the development of potential therapeutic agents and preventive actions. This review seeks to present data on the effects of stress on sleep and the different approaches used to study this relationship and possible neurobiological underpinnings and mechanisms involved. The results of numerous studies in animals indicate that increased sleep following a stressful situation is an important and adaptive behavior for recovery. However, this endogenous strategy appears to be impaired in human beings that exhibit high levels of anxiety and in animal models of anxiety-type behavior.
Keywords: sleep, paradoxical sleep, stress, HPA axis, anxiety-related behavior, animal models.