Isabela B. Antunes

The effects of paradoxical sleep deprivation on estrous cycles of the female rats.

The present purpose was to examine how sleep deprivation affects the estrous cycle of the female rat. Paradoxical sleep-deprived (PSD) adult female Wistar rats were compared to home-cage control (CTRL) on their estrous cyclicity. Forty-four PSD and forty-four CTRL female rats were distributed into 4 subgroups of 11 animals each according to the phase of estrous cycle and were subjected to sleep deprivation for 96 h by the multiple platform technique. After PSD period, vaginal estrous cycles were taken for an additional 9 days. Animals that were submitted to PSD in diestrus phase (PSD-diestrus) had their estrous cycles disrupted during the recovery period by showing a constant diestrus during the first week. As for hormone alterations, progesterone concentrations were statistically higher in PSD-diestrus compared to respective phase control and to PSD-proestrus and PSD-estrus rats while CTRL-metestrus had higher levels than CTRL-proestrus and estrus groups. Testosterone was significantly decreased in PSD-estrus in relation to PSD-proestrus and PSD-diestrus groups and was lower in CTRL-diestrus rats than in home-cage rats in proestrus. In addition, PSD-diestrus phase exhibited higher concentrations of corticosterone and lower estrogen than the respective control rats. These data indicate that PSD may modulate the ovarian hormone release through alterations in hormonal-neurochemical mechanisms.

Sleep pattern in rats under different stress modalities.

The present study was designed to evaluate the sleep pattern of rats submitted to chronic stressors (restraint, electrical footshock, swimming and cold) applied to male rats. After 48 h-baseline recording, rats were submitted to 4 days of chronic stress, and electrocorticogram recordings were carried out continuously. The stressors (footshock, swimming and cold) were applied twice a day for periods of 1 h at 9:00 and 16:00 h. Restrained animals were maintained in plastic cylinders for 22 h/day. The findings indicated that sleep efficiency, slow wave sleep (SWS) and paradoxical sleep (PS) were decreased on the third and fourth days of unpredictable shocks compared to baseline while immobilization and swimming presented reduced sleep efficiency in all 4-day recordings. Swimming led to decreased SWS, whereas augmented PS was observed on the first day compared to baseline. Immobilization produced drastic alterations in sleep patterns since it reduced SWS during the 4 days and PS at days 1 to 4 in relation to baseline. Of all stressors, cold was the only one that did not result in any statistical differences in sleep pattern during the light periods. Regarding the effect of stress compared to baseline on the dark recordings, PS was higher during cold stress periods, whereas footshock increased PS on days 2 to 4 and swimming only on day 2. Immobilization decreased PS throughout the 4 days of the stress sessions. Thus, the data suggest that different stress modalities result in distinct sleep responses, with immobilization producing the most dramatic alterations.

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.

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.

Distinct behavioral and neurochemical alterations induced by intermittent hypoxia or paradoxical sleep deprivation in rats

The current study investigated the effects of paradoxical sleep deprivation and intermittent hypoxia by examining whether a combination of the two would induce anxiety-like alterations in behavior. The neurochemical effects of these manipulations were investigated by measuring cortical, striatal and hippocampal monoamine concentrations. Wistar Hannover rats were submitted to subchronic (3 days) intermittent hypoxia exposure (alternating cycles of 2 min room air-2 min 10% O2 from 0700-1900 h) and paradoxical sleep deprivation using the single platform method. Rats were randomly assigned to four different protocols: 1) control, 2) intermittent hypoxia during the light period (12 h/day), 3) paradoxical sleep deprivation (24 h/day), and 4) intermittent hypoxia combined with paradoxical sleep deprivation. Rats subjected to intermittent hypoxia showed no modification in the behavioral or neurochemical parameters assessed. Although paradoxical sleep deprivation did not produce alterations in anxiety-like behavior, the rats did increase exploratory activity in the elevated plus-maze. Moreover, a significant increase in striatal epinephrine and hippocampal homovanilic acid (HVA) concentrations was found in the paradoxical sleep deprivation groups, but not in the intermittent hypoxia/paradoxical sleep deprivation group. Of note, both paradoxical sleep deprivation and intermittent hypoxia/paradoxical sleep deprivation groups showed an increase in plasma corticosterone concentration. These results suggest that paradoxical sleep deprivation induces behavioral alterations, and these abnormalities may reflect altered neurotransmission in the brain. When paradoxical sleep deprivation was combined with intermittent oxygen depletion, the behavioral and biochemical parameters were comparable to those of control rats.

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.

Effects of paradoxical sleep deprivation on blood parameters associated with cardiovascular risk in intact and ovariectomized rats compared with male rats

The purpose of this study was to investigate the effects of paradoxical sleep deprivation (PSD) on circulating lipoproteins (total cholesterol, HDL, LDL and triglycerides) in males as well as in intact and ovariectomized (OVX) female rats. The intact female rat group was sub-distributed according to the phase of the estrous cycle (proestrus, estrus and diestrus) allowing for comparison of the lipid profile with males and OVX rats. The results indicate that PSD significantly reduced cholesterol in intact females compared to OVX and male rats; it reduced triglycerides in all groups except in diestrus rats and increased HDL levels in male rats compared with the respective controls. PSD also increased LDL levels in male and OVX rats when compared to intact females. Examinations of cholesterol fractions revealed significant increases in HDL in control-OVX animals when compared to the other groups, whereas HDL was significantly increased after PSD in male rats. Such results suggest that the cardiovascular response in intact, OVX females and male rats is differentially regulated especially when such are submitted to PSD. Similarities in blood parameters observed between OVX and male rats are likely due to the suppression of ovarian hormone release after ovariectomy.

Effects of paradoxical sleep deprivation on genital reflexes in five rat strains.

This study examined the effects of cocaine on genital reflexes in paradoxical sleep-deprived (PSD) male rats of five strains since it has been demonstrated that this drug enhances genital reflexes in Wistar PSD rats. At the end of a 4-day period of PSD or at the equivalent time-point to control animals, cocaine or saline was acutely administered to the animals and penile erection (PE) and ejaculation (EJ) were quantified. Results indicated that PSD induced genital reflexes in all strains, and cocaine potentiated these behaviors in Wistar and Long-Evans rats. Wistar PSD rats injected with cocaine performed significantly more PE than all the other PSD + cocaine strains. The number of Wistar and Long-Evans PSD + cocaine ejaculating was significantly higher than the respective PSD + saline and control, whereas a tendency of increase was seen in relation to other groups. Wistar PSD + cocaine rats showed the highest EJ frequency compared to F344, Sprague-Dawley and Wistar-Kyoto strains, and the Long-Evans displayed more EJ than Sprague-Dawley and Wistar-Kyoto. Analysis of testosterone concentrations revealed that after sleep deprivation, Wistar, Long-Evans, and F344 rats showed significantly lower testosterone concentrations than control rats. In F344, Sprague-Dawley and Wistar-Kyoto controls rats, testosterone was significantly lower than in the control Wistar and Long-Evans. Progesterone concentrations were significantly higher in Wistar and Long-Evans PSD rats than in respective control groups. In the other strains, this hormone was significantly lower compared to the Wistar and Long-Evans PSD. This study demonstrates that genital reflexes are differently influenced by PSD associated to cocaine in five rat strains.

Noradrenergic system interacts with genital reflexes induced by cocaine in paradoxical sleep-deprived male rats.

Different doses of alpha-1, alpha-2, beta-1, and beta-2 adrenoceptor agonists or antagonists were administered to paradoxical sleep-deprived (PSD) rats prior to cocaine administration. Methoxamine reduced the percentage of rats displaying erection, whereas prazosin did not. Yohimbine significantly decreased this percentage. For beta-1 adrenoceptor drugs, both compounds reduced the percentage of rats displaying erection at the highest dose; beta-2 adrenoceptor drugs had no effect. Except for clonidine, all drugs significantly reduced the frequency of erection. Ejaculation was significantly decreased following yohimbine and beta-1 drugs, whereas it was completely abolished by prazosin. The results showed that noradrenergic drugs inhibited genital reflexes in PSD rats, with distinct responses in relation to their respective action over the adrenoceptor.

Involvement of nitric oxide in cocaine-induced erections and ejaculations after paradoxical sleep deprivation.

OBJECTIVES As nitric oxide (NO) is involved in penile erectile (PE) function and also influences the sleep-wake cycle, we speculated that NO could play a role in PE and ejaculation of paradonical sleep deprivation (PSD) rats. METHODS Animals were pretreated with N(G)-nitro-L-arginine methyl ester (L-NAME, ip) and L-arginine (ip and icv) prior to saline or cocaine injection. RESULTS Cocaine-induced PE in 90% of PSD rats, 60% of which ejaculated. L-NAME reduced the frequency of erection, but had no effect in the proportion of PSD-cocaine-injected rats displaying this response. L-NAME had no effect in saline groups. L-Arginine in PSD-saline rats reduced the proportion of animals displaying PE at the highest dose and reduced the frequency of PE at all doses in both saline and cocaine groups. The icv administration of L-arginine reduced PE only in PSD-cocaine rats. Results indicate that common to both drugs, whether it was NO synthase (NOS) inhibitor or NO precursor, was their capacity to strongly reduce PE frequency in cocaine-treated rats. Moreover, L-arginine (ip) played a relevant inhibitory role in the erection displayed by PSD rats. CONCLUSIONS Our findings suggest that the stimulating effects of PSD associated or not with cocaine on erection can be modified by alterations in the NO system.