Andressa Silva

Sleep pattern in an experimental model of osteoarthritis.

Abstract Osteoarthritis (OA) is a major healthcare burden of increasing prevalence. It has been demonstrated that the relationship between pain and sleep produces changes in sleep patterns and pain perception. However, electrophysiological studies in animal models of pain are limited. The current study examined the effect of chronic articular pain on sleep patterns in an experimental model of OA. Rats were implanted with electrodes for electrocorticography and electromyography. OA was induced in these rats by the intra‐articular administration of monosodium iodoacetate into the left knee joint. Sleep recordings were monitored during light and dark periods lasting 12 h each and were evaluated at baseline as well as on days 1, 10, 15, 20 and 28 after iodoacetate injection or assignment to sham or control groups. The pain threshold was also assessed by hot plate testing in other groups of rats at the same time points. The results demonstrated that OA significantly reduced the thermal pain threshold from day 10 until the end of experiment. OA rats exhibited reduced sleep efficiency, slow‐wave sleep, paradoxical sleep and an increased number of microarousals during the light periods compared with the baseline as well as control and sham groups. These changes in sleep pattern occurred mostly between days 10 and 28. In the dark period, sleep disturbances were also characterized by decreased sleep efficiency, slow‐wave sleep, and paradoxical sleep, although sleep was only initially fragmented. Thus, pain associated with the rat OA model causes alterations in sleep architecture by disrupting the sleep pattern.

Blockage of dopaminergic D2 receptors produces decrease of REM but not of slow wave sleep in rats after REM sleep deprivation

Dopamine (DA) has, as of late, become singled out from the profusion of other neurotransmitters as what could be called a key substance, in the regulation of the sleep-wake states. We have hypothesized that dopaminergic D(2) receptor blockage induced by haloperidol could generate a reduction or even an ablation of rapid eye movement (REM) sleep. Otherwise, the use of the selective D(2) agonist, piribedil, could potentiate REM sleep. Electrophysiological findings demonstrate that D(2) blockage produced a dramatic reduction of REM sleep during the rebound (REB) period after 96 h of REM sleep deprivation (RSD). This reduction of REM sleep was accompanied by an increment in SWS, which is possibly accounted for the observed increase in the sleep efficiency. Conversely, our findings also demonstrate that the administration of piribedil did not generate additional increase of REM sleep. Additionally, D(2) receptors were found down-regulated, in the haloperidol group, after RSD, and subsequently up-regulated after REB group, contrasting to the D(1) down-regulation at the same period. In this sense, the current data indicate a participation of the D(2) receptor for REM sleep regulation and consequently in the REM sleep/SWS balance. Herein, we propose that the mechanism underlying the striatal D(2) up-regulation is due to an effect as consequence of RSD which originally produces selective D(2) supersensitivity, and after its period probably generates a surge in D(2) expression. In conclusion we report a particular action of the dopaminergic neurotransmission in REM sleep relying on D(2) activation.

The effects of total and REM sleep deprivation on laser-evoked potential threshold and pain perception.

Summary Sleep deprivation increased the laser‐evoked potential threshold and concomitantly exerted a hyperalgesic effect in pain perception. These effects were more evident in total sleep deprivation. ABSTRACT We investigated the effects of total and rapid eye movement (REM) sleep deprivation on the thermal nociceptive threshold and pain perception using the objective laser‐evoked potential (LEP) and the subjective visual analogue scale (VAS). Twenty‐eight male adult volunteers were assigned into Control (CTRL), Total (T‐SD), and REM (REM‐SD) Sleep Deprivation groups. The T‐SD and REM‐SD volunteers were totally or selectively deprived of sleep for 2 and 4 consecutive nights, respectively. Pain parameters were measured daily during the experimental period. Volunteers were stimulated on the back of the hand by blocks of 50 diode laser pulses. Intensities increased between successive blocks, ranging from nonnoxious to noxious levels, and the LEP threshold was identified based on the evoked‐response onset. Both the LEP threshold and VAS ratings were significantly increased after the second night of T‐SD. No significant variations were observed in the REM‐SD group, suggesting a predominant role for slow wave sleep rather than selective REM‐SD in pain perception. Also, for both sleep‐deprived groups, the mean values of the LEP threshold and VAS ratings showed a gradual increase that was proportional to the SD deprivation time, followed by a decrease after 1 night of sleep restoration. These findings demonstrate a hyperalgesic modification to pain perception (as reflected by the augmented VAS) and a concomitant increase in the LEP threshold following T‐SD, an apparently contradictory effect that can be explained by differences in the ways that attention affects these pain measurements.

Distinct effects of acute and chronic sleep loss on DNA damage in rats

The aim of this investigation was to evaluate genetic damage induced in male rats by experimental sleep loss for short-term (24 and 96 h) and long-term (21 days) intervals, as well as their respective recovery periods in peripheral blood, brain, liver and heart tissue by the single cell gel (comet) assay. Rats were paradoxically deprived of sleep (PSD) by the platform technique for 24 or 96 h, or chronically sleep-restricted (SR) for 21 days. We also sought to verify the time course of their recovery after 24 h of rebound sleep. The results showed DNA damage in blood cells of rats submitted to PSD for 96 h. Brain tissue showed extensive genotoxic damage in PSD rats (both 24 and 96 h), though the effect was more pronounced in the 96 h group. Rats allowed to recover from the PSD-96 h and SR-21 days treatments showed DNA damage as compared to negative controls. Liver and heart did not display any genotoxicity activity. Corticosterone concentrations were increased after PSD (24 and 96 h) relative to control rats, whereas these levels were unaffected in the SR group. Collectively, these findings reveal that sleep loss was able to induce genetic damage in blood and brain cells, especially following acute exposure. Since DNA damage is an important step in events leading to genomic instability, this study represents a relevant contribution to the understanding of the potential health risks associated with sleep deprivation.

Gender and age differences in polysomnography findings and sleep complaints of patients referred to a sleep laboratory

Our objective was to examine the effet of gender on the sleep pattern of patients referred to a sleep laboratory. The data (questionnaires and polysomnographic recordings) were collected from a total of 2365 patients (1550 men and 815 women). The polysomnography permits an objective assessment of the sleep pattern. We included only polysomnography exams obtained with no more than one recording system in order to permit normalization of the data. Men had a significantly higher body mass index than women (28.5 +/- 4.8 vs 27.7 +/- 6.35 kg/m(2)) and had a significantly higher score on the Epworth Sleepiness Scale (10.8 +/- 5.3 vs 9.5 +/- 6.0), suggesting daytime sleepiness. Women had a significantly higher sleep latency than men, as well as a higher rapid eye movement (REM) latency. Men spent more time in stages 1 (4.6 +/- 4.1 vs 3.9 +/- 3.8) and 2 (57.0 +/- 10.5 vs 55.2 +/- 10.1) of non-REM sleep than women, whereas women spent significantly more time in deep sleep stages (3 and 4) than men (22.6 +/- 9.0 vs 19.9 +/- 9.0). The apnea/hypopnea and arousal indexes were significantly higher and more frequent in men than in women (31.0 +/- 31.5 vs 17.3 +/- 19.7). Also, periodic leg movement index did not differ significantly between genders, but rather differed among age groups. We did not find significant differences between genders in the percentage of REM sleep and sleep efficiency. The results of the current study suggest that there are specific gender differences in sleep pattern.

Sleep quality evaluation, chronotype, sleepiness and anxiety of Paralympic Brazilian athletes: Beijing 2008 Paralympic Games

Objective The objective of this study was to evaluate the sleep quality, sleepiness, chronotype and the anxiety level of Brazilian Paralympics athletes before the 2008 Beijing Paralympic Games. Design Cross-sectional study. Setting Exercise and Psychobiology Studies Center (CEPE) and Universidade Federal de São Paulo, an urban city in Brazil. Participants A total of 27 Paralympics athletes of both genders (16 men and 11 women) with an average age of 28±6 years who practised athletics (track and field events) were evaluated. Main outcome measures Sleep quality was evaluated using the Pittsburgh Scale and the Epworth Sleepiness Scale to evaluate sleepiness. Chronotype was determined by the Horne and Östberg questionnaire and anxiety through the State-Trait Anxiety Inventory. The evaluations were performed in Brazil 10 days before the competition. Results The studys results demonstrate that 83.3% of the athletes that presented excessive daytime sleepiness also had poor sleep quality. The authors noted that 71.4% were classified into the morning type and 72% of the athletes who presented a medium anxiety level also presented poor sleep quality. Athletes with poor sleep quality showed significantly lower sleep efficiency (p=0.0119) and greater sleep latency (p=0.0068) than athletes with good sleep quality. Athletes who presented excessive daytime sleepiness presented lower sleep efficiency compared to non-sleepy athletes (p=0.0241). Conclusions The authors conclude that the majority of athletes presented poor sleep quality before the competition. This information should be taken into consideration whenever possible when scheduling rest, training and competition times.

Effects of sleep loss on sleep architecture in Wistar rats: Gender-specific rebound sleep

This study was designed to examine the influence of gender on sleep rebound architecture after a 4-day paradoxical sleep deprivation period. After a 5-day baseline sleep recording, both male and female rats in different phases of the estrus cycle were submitted to paradoxical sleep deprivation for 96 h. After this period, the sleep rebound recording was evaluated for 5 days (one estrus cycle). The findings revealed that after paradoxical sleep deprivation, sleep efficiency and paradoxical sleep returned to baseline values on the second day of the light period, for all except the proestrus group. During the dark rebound period, only the female groups presented increased sleep efficiency on the first day. Paradoxical sleep returned to baseline values on the third day, except for males and the cycling females submitted to paradoxical sleep deprivation in the diestrus phase, whose baseline values returned to normal on the second day of rebound period. Thus, the females and males displayed distinct patterns as a result of sleep disruption.

Paradoxical Sleep Deprivation Influences Sexual Behavior in Female Rats

INTRODUCTION Sleep disturbances are a frequent complaint in women and are often attributed to hormonal fluctuations during the menstrual cycle. Rodents have been used as models to examine the effects of sleep deprivation on hormonal and behavioral changes. Among the many comorbidities common to sleep disorders, sexual behavior remains the least well studied. AIM To determine whether paradoxical sleep deprivation (PSD) can affect sexual receptivity (male acceptance) and proceptivity (male solicitation) behaviors in female rats. METHODS Female Wistar rats were subjected to PSD or were maintained as controls. After this period, the estrous cycle (proestrus, estrus, and diestrus) was determined, and all females were placed with a sexually experienced male. In order to investigate the role of hormones in sexual behavior, we included additional groups that were artificially induced to be sexually receptive via administration of a combination of estradiol and progesterone. MAIN OUTCOME MEASUREMENTS Receptivity and proceptivity behaviors, as well as progesterone and corticosterone concentrations were monitored. RESULTS Selective sleep loss caused a significant increase in proceptivity and receptivity behaviors in females exclusively during the proestrus phase. The rejection response was increased in PSD rats during the estrus and diestrus phases, as compared with PSD-receptive and proestrus females. PSD reduced progesterone levels during the proestrus phase relative to the respective control group during the same phase of the estrous cycle. The PSD-proestrus females that displayed the most robust sexual response exhibited greater concentrations of corticosterone than PSD-diestrus females, with an absence of sexual solicitation behaviors. CONCLUSIONS PSD produced a distinct response in the hormonal profile that was consistent with the phase of the estrous cycle. These results show that sleep loss can affect sexual motivation and might lead to important clinical implications, including alterations in female physiology and reproductive abnormalities.

Gender differences in the sleep habits of 11-13 year olds

OBJECTIVE Sleep plays an important role in the physical and emotional development of adolescents. The aim of this study was to examine gender differences in sleep habits in a sample of 11-13 year olds. METHOD The study was carried out in the city of Patos de Minas, Brazil. The study cohort was composed of 200 students (96 boys and 104 girls) attending (in the morning or in the afternoon) the 5th, 6th or 7th grades, with ages ranging from 11 to 13 years. A Sleep Questionnaire developed at the Federal University of São Paulo was used in order to evaluate student sleep habits and schedules, as well as the overall quality of sleep. RESULTS For the period between Friday night and Sunday morning, girls displayed longer sleep duration than did boys. During the week, students attending only afternoon classes woke up later than did students attending only morning classes. In addition, morning-class students showed more adverse effects on sleep, including irregular sleep/wakefulness circadian rhythms, when compared with afternoon-class students. CONCLUSION Sleep habits are affected by gender and school schedule.

Sex differences in sleep pattern of rats in an experimental model of osteoarthritis

Background: Osteoarthritis (OA) is a major healthcare burden with increasing incidence, and is characterised by the degeneration of articular cartilage. OA is associated with chronic pain and sleep disturbance.