Tathiana A. Alvarenga

Paradoxical sleep deprivation impairs acquisition, consolidation, and retrieval of a discriminative avoidance task in rats

The aim of the present study was to investigate the effects of paradoxical sleep deprivation (PSD) for 96 h on the learning/memory processes in rats submitted to the plus-maze discriminative avoidance task (PM-DAT), which simultaneously evaluates learning, memory, anxiety and motor function. Four experiments were performed in which rats were submitted to: (1) post-training and pre-test PSD; (2) post-training or pre-test PSD; (3) pre-training PSD or pre-training paradoxical sleep (PS) rebound (24 h) and (4) pre-test PSD rebound. Concerning Experiment I, post-training and pre-test PSD induced memory deficits, an anxiolytic-like behavior and an increase in locomotor activity. In Experiment II, both post-training PS-deprived and pre-test PS-deprived groups showed memory deficits per se. However, only the pre-test PS-deprived animals presented anxiolytic-like behavior and increased locomotor activity. In Experiment III, pre-training PS-deprived rats showed learning and memory deficits, anxiolytic-like behavior and increased locomotor activity. A 24h-sleep recovery period after the PSD abolished the learning and memory deficits but not anxiety and locomotor alterations. Finally, sleep rebound did not modify acquisition (Experiment III) and retrieval (Experiment IV). This study strengthened the critical role of paradoxical sleep (but not sleep rebound) in all the phases of learning and memory formation. In addition, it suggests that PSD effects on acquisition and consolidation do not seem to be related to other behavioral alterations induced by this procedure.

Single exposure to cocaine or ecstasy induces DNA damage in brain and other organs of mice

We evaluated the overall genetic damage induced by different doses of cocaine and MDMA (3,4‐Methylenedioxymethamphetamine) in several organs. One hour after intraperitoneal drug administration, mice were euthanized; peripheral blood, liver and brain were collected, and the cellular suspensions were used for the single cell gel (comet) assay. We determined that all doses of cocaine and MDMA tested were able to induce DNA damage in blood cells. Extensive genotoxic damage was induced by cocaine or MDMA at the highest doses used in liver cells. Brain cells were affected by all doses administrated. These findings demonstrate that cocaine and MDMA are potent genotoxins.

To what extent is sleep rebound effective in reversing the effects of paradoxical sleep deprivation on gene expression in the brain

Sleep is essential to maintaining health and well-being. It has been demonstrated that some of the biological alterations caused by paradoxical sleep deprivation (PSD) are not completely reversed after a period of sleep rebound (SR). The purpose of this study was to determine to what extent the specific molecular changes that occur in the rat cerebral cortex after 96 h of PSD can effectively be reversed during 24h of recovery. Total RNA from the right cerebral cortex of Wistar male rats and GeneChip Rat Genome 230 2.0 arrays were used to perform comprehensive microarray analysis of gene expression in control, PSD and SR groups. Microarray data were validated by Real Time qPCR. A total of 78 unique transcripts were differently expressed after PSD relative to control levels. These include genes related to metabolic processes, the circadian sleep-wake cycle, response to stimuli, regulation of cell proliferation and signaling pathways. After 24h of sleep rebound, approximately 62% of the sleep deprivation transcripts were again detected as differently expressed in the SR relative to the PSD group, although in the opposite direction. On the other hand, the expression of the remaining transcripts showed intermediate values between control and sleep-deprived animals. In summary, our results provide a unique set of transcripts that might be specific related to regulation of paradoxical sleep phase and sleep homeostasis processes, as well as to the biological basis of sleep disorders.

Influence of long-term food restriction on sleep pattern in male rats

The present purpose was to determine the effects of different schedules of long-term food restriction (FR) applied to rats from weaning to the 8th week. Rats were distributed into FR and ad libitum groups at weaning and fed at 7 am, at 7 pm, and finally, restricted rats fed ad libitum. The restricted rats started with 6 g/day and the food was increased by 1 g per week until reaching 15 g/day by adulthood. The rats were implanted with electrodes to record electrocorticogram/eletromyogram signals. Their wake-sleep cycles were monitored over 3 consecutive days (72 h of recording). The FR group fed at 7 am showed an increase in awake time, and decrease in slow wave sleep (SWS) and paradoxical sleep (PS) during the three light periods compared with the control recordings whereas in the dark periods, these sleep parameters were the opposite. The restricted group fed in the evening showed no statistical significances at diurnal periods; however, a significant decrease was observed in the dark recordings for awake time, but the SWS and PS were increased in relation to controls. The analysis of the 24-h period demonstrated that both FR groups presented increase in SWS time. After being FR, the rats were fed ad libitum and their sleep was monitored for 3 additional days. During the first dark recording, the decrease in awake time and increase in SWS were still present; however, as ad libitum food continued, these sleep parameters returned to control values, reestablishing the normal sleep pattern. These results suggest that dietary restriction, regardless to the feeding schedule, caused increase in total sleep time, during the active period.

Impairment of the mitochondrial electron transport chain due to sleep deprivation in mice

It has been demonstrated that sleep deprivation is associated with altered expression of genes related to metabolic processes, response to stress and inflammation, circadian sleep/wake cycles, regulation of cell proliferation and various signaling pathways. However, the molecular mechanisms underlying these changes remain poorly understood. Thus, the present study aims to characterize the function of the mitochondrial electron transport chain in the brain using an animal model of paradoxical sleep deprivation (PSD). The question of whether sleep recovery (rebound) can reverse changes found after PSD is also addressed. Adult male inbred C57BL/6J mice were randomly distributed into three groups: home-cage control, PSD and sleep rebound groups. The PSD and rebound groups were subjected to PSD for 72 h. After this sleep deprivation period, the rebound group was returned to its home cage and allowed to sleep in an undisturbed and spontaneous fashion for 24h. The mitochondrial complex I-III, complex II, succinate dehydrogenase and complex II-III activities were then measured by spectrophotometric methods in sub-mitochondrial particles extracted from the prefrontal cortex, hippocampus, striatum and hypothalamus. Our results showed a significant decrease in the activity of complex I-III in the PSD and rebound groups as compared to the control group. The complex II and II-III activity were particularly decreased in the hypothalamus of the sleep rebound group. These results are consistent with the involvement of sleep in energy metabolism and corroborate previous experiments demonstrating the importance of the hypothalamus in sleep regulation.

Food restriction or sleep deprivation: Which exerts a greater influence on the sexual behaviour of male rats?

The purpose of this study was to determine the effects of food restriction (FR) and paradoxical sleep deprivation (PSD), either alone or in combination, on sexual behaviours (mount, intromission and ejaculation) in adult male rats. Diet restriction began at weaning with 6g/day of food, and the amount of food was increased by 1g/week until it reached 15g/day amount (in adulthood). During adulthood, rats under FR and those fed ad libitum were either subjected to PSD for 96h or maintained in home-cage groups. The results indicated that both FR and ad libitum sleep-deprived groups showed a significant decrease in performance and motivation to initiate sexual behaviour, reflected by the increase in mount and intromission latencies and decreased copulatory rate. FR associated with PSD reversed the adverse effects of sleep deprivation on the number of ejaculations and inter-copulatory interval. Testosterone concentrations decreased after sleep deprivation, regardless of food availability; while progesterone was significantly higher in the FR-PSD group only. In light of the limited understanding of the link between secretion patterns and neural-hormonal control of food availability related to sexual behaviour, our data indicate that sleep loss affects sexual responses, and FR was able to restore some of the sexual parameters investigated.

Validation of commonly used reference genes for sleep-related gene expression studies

BackgroundSleep is a restorative process and is essential for maintenance of mental and physical health. In an attempt to understand the complexity of sleep, multidisciplinary strategies, including genetic approaches, have been applied to sleep research. Although quantitative real time PCR has been used in previous sleep-related gene expression studies, proper validation of reference genes is currently lacking. Thus, we examined the effect of total or paradoxical sleep deprivation (TSD or PSD) on the expression stability of the following frequently used reference genes in brain and blood: beta-actin (b-actin), beta-2-microglobulin (B2M), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and hypoxanthine guanine phosphoribosyl transferase (HPRT).ResultsNeither TSD nor PSD affected the expression stability of all tested genes in both tissues indicating that b-actin, B2M, GAPDH and HPRT are appropriate reference genes for the sleep-related gene expression studies. In order to further verify these results, the relative expression of brain derived neurotrophic factor (BDNF) and glycerol-3-phosphate dehydrogenase1 (GPD1) was evaluated in brain and blood, respectively. The normalization with each of four reference genes produced similar pattern of expression in control and sleep deprived rats, but subtle differences in the magnitude of expression fold change were observed which might affect the statistical significance.ConclusionThis study demonstrated that sleep deprivation does not alter the expression stability of commonly used reference genes in brain and blood. Nonetheless, the use of multiple reference genes in quantitative RT-PCR is required for the accurate results.

Progesterone reduces erectile dysfunction in sleep-deprived spontaneously hypertensive rats

BackgroundParadoxical sleep deprivation (PSD) associated with cocaine has been shown to enhance genital reflexes (penile erection-PE and ejaculation-EJ) in Wistar rats. Since hypertension predisposes males to erectile dysfunction, the aim of the present study was to investigate the effects of PSD on genital reflexes in the spontaneously hypertensive rat (SHR) compared to the Wistar strain. We also extended our study to examine how PSD affect steroid hormone concentrations involved in genital events in both experimental models.MethodsThe first experiment investigated the effects of PSD on genital reflexes of Wistar and SHR rats challenged by saline and cocaine (n = 10/group). To further examine the impact of the PSD on concentrations of sexual hormones, we performed a hormonal analysis of testosterone and progesterone in the Wistar and in SHR strains. Since after PSD progesterone concentrations decreased in the SHR compared to the Wistar PSD group we extended our study by investigating whether progesterone (25 mg/kg or 50 mg/kg) or testosterone (0.5 mg/kg or 1.0 mg/kg) administration during PSD would have a facilitator effect on the occurrence of genital reflexes in this hypertensive strain.ResultsA 4-day period of PSD induced PE in 50% of the Wistar rats against 10% for the SHR. These genital reflexes was potentiated by cocaine in Wistar rats whereas this scenario did not promote significant enhancement in PE and EJ in hypertensive rats, and the percentage of SHR displaying genital reflexes still figured significantly lower than that of the Wistar strain. As for hormone concentrations, both sleep-deprived Wistar and SHR showed lower testosterone concentrations than their respective controls. Sleep deprivation promoted an increase in concentrations of progesterone in Wistar rats, whereas no significant alterations were found after PSD in the SHR strain, which did not present enhancement in erectile responses. In order to explore the role of progesterone in the occurrence of genital reflexes, SHR were treated daily during the sleep deprivation period with progesterone; after the administration of this hormone and challenge with cocaine, we observed a significant increase in erectile events compared with the vehicle PSD SHR+cocaine group.ConclusionOur data showed that the low frequency of genital reflexes found in SHR sleep deprived rats may be attributed to the lower concentrations of progesterone in these rats, based on the observation that progesterone replacement increased genital reflexes in this strain.

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.

Influence of Progesterone on Sexual Performance in Male Rats

INTRODUCTION It has been documented that copulatory experience can alter or improve sexual performance in male rats. However, the hormonal basis and the number of sexual encounters needed for a rat to acquire sufficient performance remains unclear. AIM The aim of this study was to examine whether levels of testosterone and progesterone are associated with sexual performance in male rats. METHODS Adult male Wistar Hannover rats were exposed to a receptive female for 15 minutes every other day for 9 days for acquiring sexual experience. MAIN OUTCOME MEASURES After training protocol, rats were scored as low or high sexual performers. Hormonal levels (testosterone and progesterone) were evaluated in both trained and non-trained control groups. RESULTS Our results showed that a 9-day training period was not sufficient for some male rats to acquire a good level of sexual performance. While 42.5% of the rats displayed excellent sexual performance during the training sessions, 17.5% showed adequate performance, 7.5% had low sexual activity, and 32.5% of the rats did not display any sexual behaviors whatsoever. Additionally, after 4 days of training, rats with excellent/adequate performance showed a significant decrease in ejaculation latency relative to the first day of training. The rats with low or no sexual activity had lower progesterone levels relative to those displaying the highest sexual performance after 9 days of training. Testosterone, in turn, was also significantly reduced in animals with low/no sexual performance compared with excellent/adequate rats. CONCLUSION In conclusion, progesterone may be a limiting factor to promoting sexual performance in male rats.