Acute total sleep deprivation potentiates cocaine-induced hyperlocomotion in mice

Sleep deprivation is common place in modern society. Nowadays, people tend to self-impose less sleep in order to achieve professional or social goals. In the social context, late-night parties are frequently associated with higher availability of recreational drugs with abuse potential. Physiologically, all of these drugs induce an increase in dopamine release in the mesolimbic dopaminergic system, which leads to hyperlocomotion in rodents. Sleep deprivation also seems to play an important role in the events related to the neurotransmission of the dopaminergic system by potentiating its behavioral effects. In this scenario, the aim of the present study was to investigate the effects of total sleep deprivation (6h) on the acute cocaine-induced locomotor stimulation in male mice. Animals were sleep deprived or maintained in their home cages and subsequently treated with an acute i.p. injection of 15mg/kg cocaine or saline and observed in the open field. Total sleep deprivation for 6h potentiated the hyperlocomotion induced by acute cocaine administration. In addition, the cocaine sleep deprived group showed a decreased ratio central/total locomotion compared to the cocaine control group, which might be related to an increase in the impulsiveness of mice. Our data indicate that acute periods of sleep loss should be considered risk factors for cocaine abuse.

Food restriction increases long-term memory persistence in adult or aged mice

Food restriction (FR) seems to be the unique experimental manipulation that leads to a remarkable increase in lifespan in rodents. Evidences have suggested that FR can enhance memory in distinct animal models mainly during aging. However, only few studies systemically evaluated the effects FR on memory formation in both adult (3-month-old) and aged (18-24-month-old) mice. Thus, the aim of the present study was to investigate the effects of acute (12h) or repeated (12h/day for 2days) FR protocols on learning and memory of adult and aged mice evaluated in the plus-maze discriminative avoidance task (PM-DAT), an animal model that concurrently (but independently) evaluates learning and memory, anxiety and locomotion. We also investigated the possible role of FR-induced stress by the corticosterone concentration in adult mice. Male mice were kept at home cage with food ad libitum (CTRL-control condition) or subjected to FR during the dark phase of the cycle for 12h/day or 12h/2days. The FR protocols were applied before training, immediately after it or before testing. Our results demonstrated that only FR for 2days enhanced memory persistence when applied before training in adults and before testing in aged mice. Conversely, FR for 2days impaired consolidation and exerted no effects on retrieval irrespective of age. These effects do not seem to be related to corticosterone concentration. Collectively, these results indicate that FR for 2days can promote promnestic effects not only in aged mice but also in adults.

Saturated fatty acid intake can influence increase in plasminogen activator inhibitor-1 in obese adolescents

The aim of this study was to verify if saturated fatty acid intake adjusted by tertiles can influence metabolic, inflammation, and plasminogen activator inhibitor-1 (PAI-1) in obese adolescents. Body mass, height, body mass index, waist circumference, blood pressure, and body composition of 108 obese adolescents were obtained. Fasting glucose, insulin, PAI-1, and CRP were determined. Insulin resistance was assessed by Homeostasis Model Assessment (HOMA-IR) and insulin sensitivity by Quantitative Insulin Sensitivity Check Index (QUICKI). Dietetic intake was estimated by a 3-day dietary record, and volunteers were divided according to consumption of saturated fatty acids: tertile 1 [Low Saturated Fatty Acid Intake (Low-SFA): ≤12.14 g], tertile 2 [Moderate Saturated Fatty Intake (Moderate SFA intake): 12.15-20.48 g], and tertile 3 [High Saturated Fatty Acid Intake (High-SFA Intake); >20.48 g]. Statistical analysis was performed using STATISTICA 7.0 software and the significance level was set at p<0.05. The most important finding in the present study is that Moderate and High-SFA intakes presented significantly higher values of PAI-1 than Low-SFA Intake. PAI-1 was positively associated with saturated fatty intake, waist circumference, mean blood pressure, and HOMA-IR. SFA intake was predictor of PAI-1 independent of body fat, HOMA-IR and total-cholesterol. In addition, PAI-1 was an independent predictor of blood pressure. HOMA-IR and QUICKI presented significantly higher and lower, respectively, in High-SFA compared to Moderate-SFA intake. High-SFA influenced cardiovascular disease risks, since it increased PAI-1 and insulin resistance, and decreased insulin sensibility, leading to vicious cycle among food ingestion, pro-thrombotic state, and cardiovascular risks in obese adolescents.

Cardiovascular function alterations induced by acute paradoxical sleep deprivation in rats

Sleep loss has been implicated in triggering the hypertension. The goal of the present study was investigated the possible mechanisms underlying cardiovascular alterations after acute paradoxical sleep deprivation (PSD). Male Wistar rats were assigned in two experimental groups: (1) control and (2) PSD for 24 h using the modified single platform method. Paradoxical sleep deprived rats exhibited higher blood pressure, heart rate (HR) and impaired baroreceptor sensitivity. After pharmacological autonomic double blockade (propranolol and methylatropine administration), intrinsic heart rate was decreased after PSD. The PSD rats showed a reduction in the vagal tone without affecting sympathetic tone. Isoproterenol administration (0.001, 0.01 and 1 µg/kg) induced an increase in ΔHR responses in PSD group. Electrocardiographic analysis in response to β-adrenergic stimulation indicated that PSD contributed to ventricular cardiac arrhythmias. Our findings suggest that acute paradoxical sleep loss induce cardiovascular alterations, autonomic imbalance accompanied by impaired baroreflex sensitivity and increased arrhythmia susceptibility.

Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission

Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.

Effects of different physical exercises on leptin concentration in obese adolescents

In order to compare the effects of leisure physical activity (LPA), aerobic training (AT) and aerobic plus resistance training (AT + RT) as part of a 6-month interdisciplinary therapy in body composition, insulin resistance and leptin concentrations in obese adolescents, 72 volunteers (n = 24 in each group) ages 15-19 years were evaluated. Delta (Δ) body mass (kg) and Δ BMI (kg/m(2)) was different between AT and LPA groups and in AT + RT group compared to both LPA and AT groups; Δ body fat mass (kg and %) was different only in AT + RT group compared to both LPA and AT; Δ body lean mass (%) was different only in AT + RT group; Δ body lean mass (kg) was negative only in AT and positive and different from AT in AT + RT group; ΔHOMA-IR did not differ among groups; Δ leptin (ng/ml) was negative and different from LPA for both AT and AT + RT groups. In conclusion, both AT and AT + RT promoted a reduction on leptin levels, however, the adolescents subjected to AT + RT presented better results in body composition than the AT group. These results highlight the importance of associating aerobic and resistance training with nutritional and psychological approaches in the treatment of obese adolescents.

Polysomnographic Study of the Prevalence of Sleep Bruxism in a Population Sample

The goal of the current study was to estimate the prevalence of sleep bruxism (SB) in the general population using a representative sample of 1,042 individuals who answered questionnaires and underwent polysomnography (PSG) examinations. After PSG, the individuals were classified into 3 groups: absence of SB, low-frequency SB, and high-frequency SB. The results indicated that the prevalence of SB, indicated by questionnaires and confirmed by PSG, was 5.5%. With PSG used exclusively as the criterion for diagnosis, the prevalence was 7.4% regardless of SB self-reported complaints. With questionnaires alone, the prevalence was 12.5%. Of the 5.5% (n = 56) with confirmed SB, 26 were classified as low-frequency SB, and 30 as high-frequency. The episodes of SB were more frequent in stage 2 sleep, and the phasic bruxism events were more frequent than tonic or mixed events in all sleep stages in individuals with SB. A positive association was observed between SB and insomnia, higher degree of schooling, and a normal/overweight body mass index (BMI). These findings demonstrate the prevalence of SB in a population sampled by PSG, the gold standard methodology in the investigation of sleep disorders, combined with validated questionnaires (ClinicalTrials.gov, NCT00596713).

Sleep deprivation alters gene expression and antioxidant enzyme activity in mice splenocytes

Cellular defence against the formation of reactive oxygen species (ROS) involves a number of mechanisms in which antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD) play an important role. The relation between sleep deprivation and oxidative stress has not yet been completely elucidated. Although some authors did not find evidence of this relationship, others found alterations in some oxidative stress markers in response to sleep deprivation. Thus, the objective of this study was to identify changes induced by sleep deprivation in the activity and gene expression of antioxidant enzymes in mice splenocytes, ideally corroborating a better understanding of the observed effects related to sleep deprivation, which could be triggered by oxidative imbalance. Splenocytes from mice sleep deprived for 72 h showed no significant difference in CAT and CuZnSOD gene expression compared with normal sleep mice. However, sleep-deprived mice did show higher MnSOD gene expression than the control group. Concerning enzymatic activity, CuZnSOD and MnSOD significantly increased after sleep deprivation, despite the expression in CuZnSOD remained unchanged. Moreover, CAT activity was significantly lower after sleep deprivation. The data suggest that the antioxidant system is triggered by sleep deprivation, which in turn could influence the splenocytes homoeostasis, thus interfering in physiological responses.