Ovariectomy does not exacerbate the negative effects of sleep deprivation on synaptic plasticity in rats

REM sleep deprivation induced by the modified multi-platform method has detrimental effects on memory: A systematic review and meta-analysis

The modified multi-platform method (MMPM) is used to induce animal models of paradoxical sleep deprivation and impairs memory in rodents. However, variations in MMPM protocols have contributed to inconsistent conclusions across studies. This meta-analysis aimed to assess the variations of the MMPM and their effects on memory in rats and mice. A comprehensive search identified 60 studies, and 50 were included in our meta-analysis. Overall, the meta-analysis showed that the MMPM significantly reduced the percentage of time spent in target quadrants (I2 = 54 %, 95 % confidence interval [CI] = [-1.83, -1.18]) and the number of platform-area crossings (I2 = 26 %, 95 % CI = [-1.71, -1.07]) in the Morris water maze (MWM) and shortened the latency to entering the dark compartment in the passive avoidance task (I2 = 68 %, 95 % CI = [-1.36, -0.57]), but it increased the number of errors in the radial arm water maze (RAWM) (I2 = 59 %, 95 % CI = [1.29, 2.07]). Additionally, mice performed worse on the MWM, whereas rats performed worse on the passive avoidance task. More significant memory deficits were found in cross-learning and post-learning MMPM in the MWM and RAWM, respectively. This study provided evidence that the MMPM can be used in preclinical studies of memory deficits induced by paradoxical sleep deprivation.

The stress of losing sleep: Sex-specific neurobiological outcomes

Sleep is a vital and evolutionarily conserved process, critical to daily functioning and homeostatic balance. Losing sleep is inherently stressful and leads to numerous detrimental physiological outcomes. Despite sleep disturbances affecting everyone, women and female rodents are often excluded or underrepresented in clinical and pre-clinical studies. Advancing our understanding of the role of biological sex in the responses to sleep loss stands to greatly improve our ability to understand and treat health consequences of insufficient sleep. As such, this review discusses sex differences in response to sleep deprivation, with a focus on the sympathetic nervous system stress response and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We review sex differences in several stress-related consequences of sleep loss, including inflammation, learning and memory deficits, and mood related changes. Focusing on women's health, we discuss the effects of sleep deprivation during the peripartum period. In closing, we present neurobiological mechanisms, including the contribution of sex hormones, orexins, circadian timing systems, and astrocytic neuromodulation, that may underlie potential sex differences in sleep deprivation responses.

Voluntary exercise modulates learning & memory and synaptic plasticity impairments in sleep deprived female rats

Previous studies have indicated that forced exercise plays a preventive role in synaptic plasticity deficits in the hippocampus and behavioral impairments in sleep-deprived male and female rats. The objective of the present study was to evaluate the effects of voluntary exercise on early long-term potentiation (E-LTP) at the Cornu Ammonis (CA1) area of the hippocampus and behavioral functions by barnes maze and novel location tests in sleep-deprived female rats. Intact female Wistar rats were used in the present study. The exercise protocol was four weeks wheel running and the multiple platform method was applied to induce 72 h Sleep deprivation (SD). We examine the effect of exercise and/or SD on synaptic plasticity using in vivo extracellular recording in the CA1 area of the hippocampus. Spatial learning and memory examined by Barnes maze and recognition memory assessed by novel location test. Field potential recording indicated that the induction and maintenance phase of E-LTP impaired in the sleep deprived animals compared to the other groups. After 72 h SD, LTP impairments were reduced by 4 weeks of voluntary exercise but do not go back to control values. SD impairs learning and memory and exercise could improve these deficits. In conclusion, the synaptic plasticity deficit in sleep-deprived female rats was improved by voluntary exercise. Further studies are suggested to evaluate the possible underlying mechanisms.

Sex differences in sleep and sleep loss-induced cognitive deficits: The influence of gonadal hormones

Males and females can respond differentially to the same environmental stimuli and experimental conditions. Chronic sleep loss is a frequent and growing problem in many modern societies and has a broad variety of negative outcomes for health and well-being. While much has been done to explore the deleterious effects of sleep deprivation (SD) on cognition in both human and animal studies over the last few decades, very little attention has been paid to the part played by sex differences and gonadal steroids in respect of changes in cognitive functions caused by sleep loss. The effects of gonadal hormones on sleep regulation and cognitive performances are well established. Reduced gonadal function in menopausal women and elderly men is associated with sleep disturbances and cognitive decline as well as dementia, which suggests that sex steroids play a key role in modulating these conditions. Finding out whether there are sex differences in respect of the effect of insufficient sleep on cognition, and how neuroendocrine mediators influence cognitive impairment induced by SD could provide valuable insights into the best therapies for each sex. In this review, we aim to highlight the involvement of sex differences and gonadal hormone status on the severity of cognitive deficits induced by sleep deficiency in both human and animal studies.

Sex Differences in Hippocampal Memory and Kynurenic Acid Formation Following Acute Sleep Deprivation in Rats

Inadequate sleep is a prevalent problem within our society that can result in cognitive dysfunction. Elevations in kynurenic acid (KYNA), a metabolite of the kynurenine pathway (KP) of tryptophan degradation known to impact cognition, in the brain may constitute a molecular link between sleep loss and cognitive impairment. To test this hypothesis, we investigated the impact of 6 hours of sleep deprivation on memory and KP metabolism (brain and plasma) in male and female rats. Sleep-deprived males were impaired in a contextual memory paradigm, and both sexes were impaired in a recognition memory paradigm. After sleep deprivation, hippocampal KYNA levels increased significantly only in males. The response in hippocampal KYNA levels to sleep loss was suppressed in gonadectomized males, delineating a role of circulating gonadal hormones. Circulating corticosterone, which has previously been linked to KP metabolism, correlated negatively with hippocampal KYNA in sleep-deprived females, however the relationship was not significant in male animals. Taken together, our study introduces striking sex differences in brain KYNA formation and circulating corticosterone in response to sleep deprivation. Relating these findings to sex differences in cognitive outcomes after sleep deprivation may further advance the development of novel therapeutic agents to overcome sleep loss-induced cognitive dysfunction.

Mild aerobic training with blood flow restriction increases the hypertrophy index and MuSK in both slow and fast muscles of old rats: Role of PGC-1α

AIMS

Existing evidence emphasize the role of mitochondrial dysfunction in sarcopenia which is revealed as loss of skeletal muscle mass and neuromuscular junction remodeling. We assessed the effect of low-intensity aerobic training along with blood flow restriction on muscle hypertrophy index, muscle-specific kinase (MuSK), a pivotal protein of the neuromuscular junction and Peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α) in aged male rats.

MAIN METHODS

Animals groups were control (CTL), sham (Sh), leg blood flow restriction (BFR), exercise (Ex), sham + exercise (Sh + Ex), and BFR plus exercise (BFR + Ex) groups. The exercise groups were trained with low intensity exercise for 10 weeks. 48 h after the last training session, animals were sacrificed under anesthesia. Soleus and EDL muscles were isolated, hypertrophy index was estimated and MuSK and PGC-1α were measured by western blot method.

KEY FINDINGS

Hypertrophy index enhanced in soleus and Extensor digitorum longus (EDL) muscles of BFR + Ex group (P < 0.01 versus CTL and Sh groups, and P < 0.001 versus other groups). The MuSK protein of soleus and EDL muscles increased in BFR + Ex group (P < 0.01 and P < 0.001, respectively) in comparison with CTL and Sh groups. In BFR + Ex group, the PGC-1α protein increased in both soleus and EDL (P < 0.001 compared to other groups). Also the PGC-1α of soleus muscle was higher in Ex and Sh + Ex groups versus CTL and Sh groups (P < 0.05).

SIGNIFICANCE

Findings suggest that low endurance exercise plus BFR improves the MuSK and hypertrophy index of both slow and fast muscles of elderly rats probably through the rise of PGC-1α expression.

Long-term Low-Intensity Endurance Exercise along with Blood-Flow Restriction Improves Muscle Mass and Neuromuscular Junction Compartments in Old Rats

BACKGROUND

During the aging process, muscle atrophy and neuromuscular junction remodeling are inevitable. The present study aimed to clarify whether low-intensity aerobic exercise along with limb blood-flow restriction (BFR) could improve aging-induced muscle atrophy and nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction.

METHODS

Forty-eight male Wistar rats, aged 23-24 months, were randomly divided into control, sham (Sh: subjected to surgery without BFR), BFR (subjected to BFR), exercise (Ex: subjected to 10 weeks of low-intensity exercise), Sh+Ex, and BFR+Ex groups. Forty-eight hours after the last training session, the animals were sacrificed and their soleus and extensor digitorum longus (EDL) muscles were removed. The hypertrophy index was calculated, and molecular parameters were measured using western blotting. Statistical analysis was done with ANOVA using SPSS (version 20), with a P<0.05 as the level of significance.

RESULTS

The control and Sh groups showed weight gain (P=0.001), whereas the Ex, Sh+Ex, and BFR+Ex groups had significant weight loss (P<0.001). The hypertrophy index of the soleus was significantly higher in the BFR+Ex group than in the control, Sh, and BFR groups (P<0.001). BFR+Ex induced significant hypertrophic effects on the EDL (P<0.001 vs. the control, Sh, Ex, and Sh+Ex groups, and P=0.006 vs. the BFR group). BFR+Ex also increased nAChRs in the soleus (P=0.02 vs. the control and Sh groups) and the EDL (P=0.008 vs. the control and Sh groups).

CONCLUSION

BFR plus mild exercise is a safe method with potential beneficial effects in protecting and augmenting muscle mass and nAChR clustering at the neuromuscular junction in old rats.