Ricardo Borges Machado

Sleep deprivation induced by the modified multiple platform technique: quantification of sleep loss and recovery.

Vigilance status was continually monitored in socially stable groups of rats exposed to the modified multiple platform (MMP) technique for sleep deprivation. For comparison, sleep parameters were also monitored in socially isolated rats deprived of sleep by the single platform (SP) method. In all cases, sleep was continuously recorded during baseline, during 96 h of sleep deprivation and during 4 days of recovery. Both multiple- and single-platform techniques completely abolished paradoxical sleep (PS) during the deprivation period, but also resulted in significant decreases in slow wave sleep (SWS) (-31% and -37%, respectively). Unexpectedly, animals on large platforms, which are normally intended as controls, also showed significant reductions in PS and SWS, and these effects were more pronounced in rats deprived in groups than in animals deprived in isolation. Another control preparation, rats placed on wire-mesh grids in the deprivation tank, also showed PS reduction (-39%) but no loss of SWS during the 4 test days. Paradoxical sleep rebound was observed in the first 24 h in all groups, except for grid controls. Overall, no significant differences were found between single- and multiple-platform procedures during the 4 days of deprivation. However, sleep rebound was more pronounced in MMP-deprived rats than in SP-deprived rats. Sleep loss in both control groups may reflect residual effect of stress that remain in the platform technique. These findings indicate that the MMP technique is effective in inducing PS deprivation (PSD). However, the fact that SWS is also affected may have implications for conclusions on paradoxical sleep function based upon paradoxical sleep deprivation.

Role of hippocampal oxidative stress in memory deficits induced by sleep deprivation in mice.

Numerous animal and clinical studies have described memory deficits following sleep deprivation. There is also evidence that the absence of sleep increases brain oxidative stress. The present study investigates the role of hippocampal oxidative stress in memory deficits induced by sleep deprivation in mice. Mice were sleep deprived for 72 h by the multiple platform method-groups of 4-6 animals were placed in water tanks, containing 12 platforms (3 cm in diameter) surrounded by water up to 1 cm beneath the surface. Mice kept in their home cage or placed onto larger platforms were used as control groups. The results showed that hippocampal oxidized/reduced glutathione ratio as well as lipid peroxidation of sleep-deprived mice was significantly increased compared to control groups. The same procedure of sleep deprivation led to a passive avoidance retention deficit. Both passive avoidance retention deficit and increased hippocampal lipid peroxidation were prevented by repeated treatment (15 consecutive days, i.p.) with the antioxidant agents melatonin (5 mg/kg), N-tert-butyl-alpha-phenylnitrone (200 mg/kg) or vitamin E (40 mg/kg). The results indicate an important role of hippocampal oxidative stress in passive avoidance memory deficits induced by sleep deprivation in mice.

Different stress modalities result in distinct steroid hormone responses by male rats

Since both paradoxical sleep deprivation (PSD) and stress alter male reproductive function, the purpose of the present study was to examine the influence of PSD and other stressors (restraint, electrical footshock, cold and forced swimming, N = 10 per group) on steroid hormones in adult Wistar male rats. Rats were submitted to chronic stress for four days. The stressors (footshock, cold and forced swimming) 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 whereas PSD was continuous. Hormone determination was measured by chemiluminescent enzyme immunoassay (testosterone), competitive immunoassay (progesterone) and by radioimmunoassay (corticosterone, estradiol, estrone). The findings indicate that PSD (13.7 ng/dl), footshock (31.7 ng/dl) and cold (35.2 ng/dl) led to lower testosterone levels compared to the swimming (370.4 ng/dl) and control (371.4 ng/dl) groups. However, progesterone levels were elevated in the footshock (4.5 ng/ml) and PSD (5.4 ng/ml) groups compared to control (1.6 ng/ml), swimming (1.1 ng/ml), cold (2.3 ng/ml), and restrained (1.2 ng/ml) animals. Estrone and estradiol levels were reduced in the PSD, footshock and restraint groups compared to the control, swimming and cold groups. A significant increase in corticosterone levels was found only in the PSD (299.8 ng/ml) and footshock (169.6 ng/ml) groups. These changes may be thought to be the full steroidal response to stress of significant intensity. Thus, the data suggest that different stress modalities result in distinct steroid hormone responses, with PSD and footshock being the most similar.

Sleep disturbance induced by substance P in mice

UNLABELLED Substance P (SP) and neurokinins have been implicated in modulating pain and mood but little is known about their effect on sleep-wake behavior. The purpose of the present study was to examine the possible involvement of SP in sleep-wake mechanisms without activation of painful responses. Electrophysiological recordings of the sleep-wake cycle were conducted in C57BL/6J male mice that had intracerebral ventricular cannula inserted for drug administration. Initially, in order to determine the highest dose of SP that would not induce nociceptive response, 10 animals per group received administration of either SP doses or artificial cerebrospinal fluid (CSF-sham group) through the cannula and were assessed by the hot plate test. The sleep-wake cycle of two other groups of mice was recorded for 24 h before (baseline) and after receiving CSF (n=10) or SP-1 mM (n=11), dose that had been determined in the previous hot plate test. SP interfered with sleep, when compared to baseline and to sham group, by reducing sleep efficiency, increasing latency of sleep and the number of awakening bouts. To examine the reversal of SP effects, eight mice were administered with an NK1 receptor antagonist before SP administration. Prior administration of the NK1 antagonist prevented the disturbances in sleep. CONCLUSIONS The results suggest that SP produces disturbances in sleep, likely mediated by the NK1 receptor.

Sleep homeostasis in rats assessed by a long-term intermittent paradoxical sleep deprivation protocol

Numerous studies have evaluated the sleep homeostasis of rats after short- or long-periods of sleep deprivation, but none has assessed the effects of prolonged sleep restriction on the rats sleep pattern. The purpose of the present study, therefore, was to evaluate the sleep homeostasis of rats under a protocol of chronic sleep restriction. Male Wistar rats were implanted with electrodes for EEG and EMG recordings. Using the single platform method, the animals were submitted to 18 h of sleep restriction, beginning at 16:00 h (lights on at 07:00 h), followed by a 6 h sleep window (from 10:00 h to 16:00 h) for 21 days. Immediately after this period, rats were allowed to sleep freely for 4 days (recovery period). The sleep-wake cycle was recorded throughout the entire experiment and the results showed that during the 6h sleep window there was an increase on the percentage of sleep time, reflected by augmented time in high amplitude slow wave sleep and in paradoxical sleep, when compared to baseline sleep, whereas bouts of awakening longer than 1.5 min were greatly reduced, with the animals exhibiting a monophasic-type sleep pattern. During the deprivation period, paradoxical sleep was abolished. High amplitude slow wave sleep was also greatly affected by the protocol. Nonetheless, one day of recovery was sufficient to restore the normal sleep pattern. These findings indicate that this protocol was capable to induce many changes in the rats sleep patterns, suggesting that during the 6h sleep window there is a sleep adaptive homeostatic process.

Increased hypocretin-1 levels in cerebrospinal fluid after REM sleep deprivation

Rat cisternal (CSF) hypocretin-1 in cerebrospinal fluid was measured after 6 or 96 h of REM sleep deprivation and following 24 h of REM sleep rebound. REM deprivation was found to increase CSF hypocretin-1 collected at zeitgeber time (ZT) 8 but not ZT0. Decreased CSF hypocretin levels were also observed at ZT8 after 24 h of REM sleep rebound. These results suggest that REM sleep deprivation activates and REM sleep rebound inhibits the hypocretin system. Increased hypocretin tone during REM deprivation may be important in mediating some of the effects of REM sleep deprivation such as antidepressant effects, hyperphagia and increased sympathetic activity.

Chronic stress during paradoxical sleep deprivation increases paradoxical sleep rebound: Association with prolactin plasma levels and brain serotonin content

Previous studies suggest that stress associated to sleep deprivation methods can affect the expression of sleep rebound. In order to examine this association and possible mechanisms, rats were exposed to footshock stress during or immediately after a 96-h period of paradoxical sleep deprivation (PSD) and their sleep and heart rate were recorded. Control rats (maintained in individual home cages) and paradoxical sleep-deprived (PS-deprived) rats were distributed in three conditions (1) no footshock--NF; (2) single footshock--SFS: one single footshock session at the end of the PSD period (6-8 shocks per minute; 100 ms; 2 mA; for 40 min); and (3) multiple footshock--MFS: footshock sessions with the same characteristics as described above, twice a day throughout PSD (at 7:00 h and 19:00 h) and one extra session before the recovery period. After PSD, animals were allowed to sleep freely for 72 h. Additional groups were sacrificed at the end of the sleep deprivation period for blood sampling (ACTH, corticosterone, prolactin and catecholamine levels) and brain harvesting (monoamines and metabolites). Neither SFS nor MFS produced significant alterations in the sleep patterns of control rats. All PS-deprived groups exhibited increased heart rate which could be explained by increased dopaminergic activity in the medulla. As expected, PS deprivation induced rebound of paradoxical sleep in the first day of recovery; however, PSD+MFS group showed the highest rebound (327.3% above the baseline). This group also showed intermediate levels of corticosterone and the highest levels of prolactin, which were positively correlated with the length of PS episodes. Moreover, paradoxical sleep deprivation resulted in elevation of the serotonergic turnover in the hypothalamus, which partly explained the hormonal results, and in the hippocampus, which appears to be related to adaptive responses to stress. The data are discussed in the realm of a prospective importance of paradoxical sleep for processing of traumatic events.

Modulation of sickness behavior by sleep: The role of neurochemical and neuroinflammatory pathways in mice

Activation of the immune system elicits several behavioral changes that are collectively called sickness behavior and consists in a strategy to overcome infection. Sleep deprivation can increase susceptibility to pathogens and to behavioral alterations. Thus, the present study aimed to determine how paradoxical sleep deprivation (PSD) affects the behavioral and neurochemical responses to lipopolysaccharide (LPS, potent activator of the immune response). Adult inbred mice were paradoxical sleep deprived (72 h), whereas the control group was kept in their home cages. Both groups received either an injection of saline or LPS (5, 10 or 20 microg/animal ip) before behavioral tasks and tissue collection. During the recovery sleep period, LPS provoked a strong inhibition of sleep rebound due to a suppression of paradoxical sleep. PSD increased the susceptibility of mice to LPS-induced immobility in the open field, which was capable of affecting the anxiety-like behavior also. These altered behavioral responses to LPS were accompanied by reduction in dopamine turnover within the striatum and increased expression of cyclooxygenase-2 in the cortex. The study provides some insights into how the sleep-wake cycle affects the expression of sickness behavior induced by LPS.

REM Sleep Rebound as an Adaptive Response to Stressful Situations

Stress and sleep are related to each other in a bidirectional way. If on one hand poor or inadequate sleep exacerbates emotional, behavioral, and stress-related responses, on the other hand acute stress induces sleep rebound, most likely as a way to cope with the adverse stimuli. Chronic, as opposed to acute, stress impairs sleep and has been claimed to be one of the triggering factors of emotional-related sleep disorders, such as insomnia, depressive- and anxiety-disorders. These outcomes are dependent on individual psychobiological characteristics, conferring even more complexity to the stress-sleep relationship. Its neurobiology has only recently begun to be explored, through animal models, which are also valuable for 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 as well as possible neurobiological underpinnings and mechanisms involved. The results of numerous studies in humans and animals indicate that increased sleep, especially the rapid eye movement phase, following a stressful situation is an important adaptive behavior for recovery. However, this endogenous advantage appears to be impaired in human beings and rodent strains that exhibit high levels of anxiety and anxiety-like behavior.

Comparison of the sleep pattern throughout a protocol of chronic sleep restriction induced by two methods of paradoxical sleep deprivation

The purpose of the present study was to evaluate the sleep homeostasis of rats submitted to a protocol of chronic sleep restriction by two methods and to evaluate the sleep characteristics during the recovery period. The sleep restriction protocol was accomplished by sleep depriving rats for 18 h everyday for 21 days, using the single platform method (SPM) or the modified multiple platform method (MMPM) of paradoxical sleep (PS) deprivation. Rats were allowed to sleep for 6 h (from 10:00 to 16:00; starting 3 h after lights on) in their individual home-cages, during which their sleep was recorded. At the end of the sleep restriction protocol, rats were recorded in their home-cages for 4 days, where they could sleep freely. Both methods used to induce chronic sleep restriction were effective, in sofar as they resulted in augmented sleep time during the 6h-sleep period, with very few bouts of wakening. Although comparison between the methods did not reveal differences, sleep restriction under MMPM produced a more consistent daily rebound, mainly of paradoxical sleep, with longer episodes. These results showed distinct sleep recovery patterns, suggesting a possible role of the waking experiences (i.e. immobilization stress, social interaction) acting on sleep consolidation.