Forced and voluntary exercise differentially affect brain and behavior

Physical exercise restores adult neurogenesis deficits induced by simulated microgravity

Cognitive impairments have been reported in astronauts during spaceflights and documented in ground-based models of simulated microgravity (SMG) in animals. However, the neuronal causes of these behavioral effects remain largely unknown. We explored whether adult neurogenesis, known to be a crucial plasticity mechanism supporting memory processes, is altered by SMG. Adult male Long-Evans rats were submitted to the hindlimb unloading model of SMG. We studied the proliferation, survival and maturation of newborn cells in the following neurogenic niches: the subventricular zone (SVZ)/olfactory bulb (OB) and the dentate gyrus (DG) of the hippocampus, at different delays following various periods of SMG. SMG exposure for 7 days, but not shorter periods of 6 or 24 h, resulted in a decrease of newborn cell proliferation restricted to the DG. SMG also induced a decrease in short-term (7 days), but not long-term (21 days), survival of newborn cells in the SVZ/OB and DG. Physical exercise, used as a countermeasure, was able to reverse the decrease in newborn cell survival observed in the SVZ and DG. In addition, depending on the duration of SMG periods, transcriptomic analysis revealed modifications in gene expression involved in neurogenesis. These findings highlight the sensitivity of adult neurogenesis to gravitational environmental factors during a transient period, suggesting that there is a period of adaptation of physiological systems to this new environment.

Exploring the neuroprotective role of physical activity in cerebral small vessel disease

Cerebral small vessel disease (cSVD) is a common neurological finding characterized by abnormalities of the small blood vessels in the brain. Previous research has established a strong connection between cSVD and stroke, as well as neurodegenerative disorders, notably Alzheimer's disease (AD) and other dementias. As the search for effective interventions continues, physical activity (PA) has emerged as a potential preventative and therapeutic avenue. This review synthesizes the human and animal literature on the influence of PA on cSVD, highlighting the importance of determining optimal exercise protocols, considering aspects such as intensity, duration, timing, and exercise type. Furthermore, the necessity of widening the age bracket in research samples is discussed, ensuring a holistic understanding of the interventions across varying pathological stages of the disease. The review also suggests the potential of exploring diverse biomarkers and risk profiles associated with clinically significant outcomes. Moreover, we review findings demonstrating the beneficial effects of PA in various rodent models of cSVD, which have uncovered numerous mechanisms of neuroprotection, including increases in neuroplasticity and integrity of the vasculature and white matter; decreases in inflammation, oxidative stress, and mitochondrial dysfunction; and alterations in amyloid processing and neurotransmitter signaling. In conclusion, this review highlights the potential of physical activity as a preventive strategy for addressing cSVD, offering insights into the need for refining exercise parameters, diversifying research populations, and exploring novel biomarkers, while shedding light on the intricate mechanisms through which exercise confers neuroprotection in both humans and animal models.

Effects of voluntary and forced physical exercise on the retinal health of aging Wistar rats

Aging is accompanied by an increased prevalence of degenerative conditions, including those affecting ocular health, which significantly impact quality of life and increase the burden on healthcare systems. Among these, retinal aging is of particular concern due to its direct link to vision impairment, a leading cause of disability in the elderly. Vision loss in the aging population is associated with heightened risks of cognitive decline, social isolation, and morbidity. This study addresses the critical gap in our understanding of modifiable lifestyle factors, such as physical exercise, that may mitigate retinal aging and its related pathologies. We investigated the effects of different exercise regimens-voluntary (recreational-type) and forced (high-intensity)-on the retinal health of aging Wistar rats (18-month-old), serving as a model for studying the translational potential of exercise interventions in humans. Male Wistar rats were divided into four groups: a young control (3-month-old) for baseline comparison, an aged sedentary control, an aged group engaging in voluntary exercise via a running wheel in their cage, and an aged group subjected to forced exercise on a treadmill for six sessions of 20 min each per week. After a 6-month experimental period, we assessed retinal function via electroretinography (ERG), measured retinal thickness histologically, and analyzed protein expression changes relevant to oxidative stress, inflammation, and anti-aging mechanisms. Our findings reveal that voluntary exercise positively impacts retinal function and morphology, reducing oxidative stress and inflammation markers while enhancing anti-aging protein expression. In contrast, forced exercise showed diminished benefits. These insights underscore the importance of exercise intensity and preference in preserving retinal health during aging. The study highlights the potential of recreational physical activity as a non-invasive strategy to counteract retinal aging, advocating for further research into exercise regimens as preventative therapies for age-related ocular degenerations.

Exercise protects the hypothalamus morphology from the deleterious effects of high sucrose diet consumption

A growing body of evidence suggests that elevated sucrose intake may contribute to the development of neurological disorders. Recognizing that regular exercise has the potential to reduce the occurrence of neuromuscular disorders, the present research investigated the impact of exercise on the redox status of the hypothalamus in mitigating the adverse effects associated with high sucrose intake. Forty Wistar albino rats were subjected to a high sucrose diet, with some groups engaging in exercise for a duration of 3 months. The exercise regimen was found to sustain the redox balance in the hypothalamus. In summary, the consumption of a high sucrose diet resulted in the disturbance of the histological morphology of the hypothalamus, accompanied by an increased percentage of caspase-3 positive cells. Additionally, the high sucrose diet disrupted the oxidant/antioxidant ratio in favor of oxidants, leading to elevated levels of AOPPs and AGEP. Conversely, exercise was effective in restoring most of these values to levels approximating the control group, indicating a potential protective effect of regular exercise against the detrimental impacts of high sucrose dietary consumption on the hypothalamus. Graphical abstract.

The unconditioned fear response in vertebrates deficient in dystrophin

Dystrophin loss due to mutations in the Duchenne muscular dystrophy (DMD) gene is associated with a wide spectrum of neurocognitive comorbidities, including an aberrant unconditioned fear response to stressful/threat stimuli. Dystrophin-deficient animal models of DMD demonstrate enhanced stress reactivity that manifests as sustained periods of immobility. When the threat is repetitive or severe in nature, dystrophinopathy phenotypes can be exacerbated and even cause sudden death. Thus, it is apparent that enhanced sensitivity to stressful/threat stimuli in dystrophin-deficient vertebrates is a legitimate cause of concern for patients with DMD that could impact neurocognition and pathophysiology. This review discusses our current understanding of the mechanisms and consequences of the hypersensitive fear response in preclinical models of DMD and the potential challenges facing clinical translatability.

Atlas of exercise-induced brain activation in mice

OBJECTIVES

There is significant interest in uncovering the mechanisms through which exercise enhances cognition, memory, and mood, and lowers the risk of neurodegenerative diseases. In this study, we utilize forced treadmill running and distance-matched voluntary wheel running, coupled with light sheet 3D brain imaging and c-Fos immunohistochemistry, to generate a comprehensive atlas of exercise-induced brain activation in mice.

METHODS

To investigate the effects of exercise on brain activity, we compared whole-brain activation profiles of mice subjected to treadmill running with mice subjected to distance-matched wheel running. Male mice were assigned to one of four groups: a) an acute bout of voluntary wheel running, b) confinement to a cage with a locked running wheel, c) forced treadmill running, or d) placement on an inactive treadmill. Immediately following each exercise or control intervention, blood samples were collected for plasma analysis, and brains were collected for whole-brain c-Fos quantification.

RESULTS

Our dataset reveals 255 brain regions activated by acute exercise in mice, the majority of which have not previously been linked to exercise. We find a broad response of 140 regulated brain regions that are shared between voluntary wheel running and treadmill running, while 32 brain regions are uniquely regulated by wheel running and 83 brain regions uniquely regulated by treadmill running. In contrast to voluntary wheel running, forced treadmill running triggers activity in brain regions associated with stress, fear, and pain.

CONCLUSIONS

Our findings demonstrate a significant overlap in neuronal activation signatures between voluntary wheel running and distance-matched forced treadmill running. However, our analysis also reveals notable differences and subtle nuances between these two widely used paradigms. The comprehensive dataset is accessible online at www.neuropedia.dk, with the aim of enabling future research directed towards unraveling the neurobiological response to exercise.

Impact of enriched environment on motor performance and learning in mice

Neuroscience heavily relies on animal welfare in laboratory rodents as it can significantly affect brain development, cognitive function and memory formation. Unfortunately, laboratory animals are often raised in artificial environments devoid of physical and social stimuli, potentially leading to biased outcomes in behavioural assays. To assess this effect, we examined the impact of social and physical cage enrichment on various forms of motor coordination. Our findings indicate that while enriched-housed animals did not exhibit faster learning in eyeblink conditioning, the peak timing of their conditioned responses was slightly, but significantly, improved. Additionally, enriched-housed animals outperformed animals that were housed in standard conditions in the accelerating rotarod and ErasmusLadder test. In contrast, we found no significant effect of enrichment on the balance beam and grip strength test. Overall, our data suggest that an enriched environment can improve motor performance and motor learning under challenging and/or novel circumstances, possibly reflecting an altered state of anxiety.

Adulthood effects of developmental exercise in rats

Exercise is known to promote efficient function of stress circuitry. The developing brain is malleable and thus exercise during adolescence could potentially exert lasting beneficial effects on the stress response that would be detectable in adulthood. The current study determined whether adolescent wheel running was associated with reduced stress response in adulthood, 6 weeks after cessation of exercise. Male and female adolescent rats voluntarily ran for 6 weeks and then were sedentary for 6 weeks prior to 10 days of chronic restraint stress in adulthood. Fecal corticosterone levels were measured during stress, and escape from the restraint tube was assessed on the final day as a proxy for depressive-like behavior. Anxiety-like behavior was measured 24 h later with the elevated plus maze and locomotor behaviors with the open field. Brain and body measurements were taken immediately following behavioral testing. Developmental exercise and adulthood stress both exerted independent effects on physiological and behavioral outcomes in adulthood. Exercise history increased the odds ratio of escape from restraint stress in males, but did not influence other stress-induced behaviors. In summary, exercise early in life exerted lasting effects, but did not substantially alter the adulthood response to restraint stress.

Impact of physical activity on brain oxidative metabolism and intrinsic capacities in young swiss mice fed a high fat diet

Type 2 diabetes and obesity characterized by hallmarks of insulin resistance along with an imbalance in brain oxidative metabolism would impair intrinsic capacities (ICs), a new concept for assessing mental and physical functioning. Here, we explored the impact of physical activity on antioxidant responses and oxidative metabolism in discrete brain areas of HFD or standard diet (STD) fed mice but also its consequences on specific domains of ICs. 6-week-old Swiss male mice were exposed to a STD or a HFD for 16 weeks and half of the mice in each group had access to an activity wheel and the other half did not. As expected HFD mice displayed peripheral insulin resistance but also a persistent inhibition of aconitase activity in cortices revealing an increase in mitochondrial reactive oxygen species (ROS) production. Animals with access to the running wheel displayed an improvement of insulin sensitivity regardless of the diet factor whereas ROS production remained impaired. Moreover, although the access of the running wheel did not influence mitochondrial biomass, in the oxidative metabolism area, it produced a slight decrease in brain SOD1 and catalase expression notably in HFD fed mice. At the behavioural level, physical exercise produced anxiolytic/antidepressant-like responses and improved motor coordination in both STD and HFD fed mice. However, this non-pharmacological intervention failed to enhance cognitive performance. These findings paint a contrasting landscape about physical exercise as a non-pharmacological intervention for positively orienting the aging trajectory.

Potential resilience treatments for orangutans (Pongo spp.): Lessons from a scoping review of interventions in humans and other animals

Wild orangutans (Pongo spp.) rescued from human-wildlife conflict must be adequately rehabilitated before being returned to the wild. It is essential that released orangutans are able to cope with stressful challenges such as food scarcity, navigating unfamiliar environments, and regaining independence from human support. Although practical skills are taught to orangutans in rehabilitation centres, post-release survival rates are low. Psychological resilience, or the ability to 'bounce back' from stress, may be a key missing piece of the puzzle. However, there is very little knowledge about species-appropriate interventions which could help captive orangutans increase resilience to stress. This scoping review summarises and critically analyses existing human and non-human animal resilience literature and provides suggestions for the development of interventions for orangutans in rehabilitation. Three scientific databases were searched in 2021 and 2023, resulting in 63 human studies and 266 non-human animal studies. The first section brings together human resilience interventions, identifying common themes and assessing the applicability of human interventions to orangutans in rehabilitation. The second section groups animal interventions into categories of direct stress, separation stress, environmental conditions, social stress, and exercise. In each category, interventions are critically analysed to evaluate their potential for orangutans in rehabilitation. The results show that mild and manageable forms of intervention have the greatest potential benefit with the least amount of risk. The study concludes by emphasising the need for further investigation and experimentation, to develop appropriate interventions and measure their effect on the post-release survival rate of orangutans.

Immunoinflammatory Response to Acute Noise Stress in Male Rats Adapted with Different Exercise Training

Objective

Noise pollution is a kind of stress that impairs various physiological functions. This study evaluated the effect of high-intensity interval training (HIIT) and moderate-intensity continuous training (MCT) on corticosterone, interleukin-6 (IL-6), and monocyte responses to acute noise stress in male rats.

Design

Forty-two male Wistar rats were divided into seven groups, including control which was assessed at the beginning, control time which was assessed simultaneously with experimental groups (CT), HIIT, MCT, HIIT followed by noise stress (HIIT+S), MCT followed by noise stress (MCT+S), and noise stress. HIIT and MCT were performed for 8 weeks. Noise stress was induced for one session. Blood samples were taken 48 hours after the last exercise session in training and CT groups and immediately after acute noise stress in stress groups of HIIT+S, MCT+S, and noise stress.

Results

In response to acute noise stress, MCT and HIIT adaptations increased corticosterone, while reduced monocytes compared to CT. MCT increased basal corticosterone and IL-6 and decreased monocytes; however, in response to acute noise stress, corticosterone was higher and monocyte count was lower in the HIIT+S group. Regarding the effect of training, corticosterone and monocytes in MCT were higher than in HIIT. The serum level of IL-6 was lower in MCT than CT group, while it was not significantly different between stress groups.

Conclusion

In response to noise stress, previous exercise, especially HIIT, increased stress while did not increase inflammatory and innate immune response.

High-intensity interval training improves long-term memory and increases hippocampal antioxidant activity and BDNF levels in ovariectomized Wistar rats

Menopause is the period in which women cease to produce the hormone estrogen, which can trigger physiological, cognitive, and behavioral changes. In this context, alternatives are needed that can reduce the effects provided by menopause, specifically in terms of cognitive and behavioral aspects. High-intensity interval training (HIIT) is an exercise protocol that has shown the potential to improve cognition by promoting an increase in antioxidant defenses and BDNF levels. Therefore, the aim of this study was to evaluate the effects of HIIT on behavior and hippocampal neurochemistry in ovariectomized adult rats. Four groups of rats were divided into: females without ovariectomy surgery and sedentary (SHAM-SED); females with ovariectomy surgery and sedentary (OVX-SED); females without ovariectomy surgery and trained (SHAM-HIIT); females with ovariectomy surgery and trained (OVX-HIIT). After the surgical procedure and the HIIT protocol, the animals underwent anxiety (elevated plus maze and open field) and memory (novel object recognition) tests. Corticosterone was measured in blood and BDNF levels and redox status were evaluated in the hippocampus. The OVX-SED group showed low BDNF levels and antioxidant enzymes, which may be linked to the observed memory impairments. The HIIT protocol (SHAM-HIIT and OVX-HIIT groups) increased the BDNF levels and antioxidant enzymes in the hippocampus, improving the animals' memory. However, HIIT also led to increased plasma corticosterone and anxiety-like behaviors. The ovariectomy procedure induced memory impairment probably due to reductions in hippocampal BDNF levels and redox imbalance. The HIIT protocol demonstrates promising results as an alternative to improve memory in ovariectomized rats.

Static stretching of the ankle prevents cold hypersensitivity associated with limb immobilization in model mice

BACKGROUND

Limb immobilization is considered to contribute to limb pain including hyperalgesia. Approximately 50% of patients with such chronic limb pain complain that their abnormal pain worsens after exposure to cold. However, there have been few studies on the relationship between limb immobilization and cold hypersensitivity. The aim of this study was to examine whether limb immobilization induces cold hypersensitivity, and whether physical exercise such as ankle stretching prevents its induction in model mice.

METHOD

We used forty-four 8-week-old male C57Bl/6J mice, consisting of 32 immobilized mice and 12 control mice. The bilateral hind limbs of the mice were immobilized by a thermoplastic cast. After limb-immobilization for 1 week, changes in mechanical, thermal and cold hypersensitivity, and the expression levels of TRPV1, TRPA1, TRPM8, IL-1β, IL-6, and TNFα in the spinal cord, dorsal root ganglia and the affected hind paw were evaluated in comparison with those in the control mice. In addition, we examined the effect of ankle stretching on the hypersensitivity and expression levels in the limb-immobilized mice.

RESULTS

Mechanical, thermal and cold hypersensitivity were significantly increased in the limb-immobilized mice. In addition, ankle stretching during the immobilization period significantly prevented the increases in those hypersensitivities. There were no significant differences in the expression levels of TRPV1, TRPA1 and TRPM8 among the control, and limb-immobilized mice with and without ankle stretching. The expression levels of IL-1 and IL-6 were significantly increased in the immobilized hind limb paw. Furthermore, ankle stretching significantly prevented the increases in their expression levels.

CONCLUSION

Limb-immobilization induced cold hypersensitivity as well as mechanical and thermal hypersensitivity, and ankle stretching significantly prevented the hypersensitivity induction in the model mice. It would be of great interest to clarify whether a patient with limb-immobilization experiences cold hypersensitivity and whether ankle stretching might prevent hypersensitivity induction in the future.

Effects of Voluntary Physical Exercise on the Neurovascular Unit in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Histopathologically, AD presents two pathognomonic hallmarks: (1) neurofibrillary tangles, characterized by intracellular deposits of hyperphosphorylated tau protein, and (2) extracellular amyloid deposits (amyloid plaques) in the brain vasculature (cerebral amyloid angiopathy; CAA). It has been proposed that vascular amyloid deposits could trigger neurovascular unit (NVU) dysfunction in AD. The NVU is composed primarily of astrocytic feet, endothelial cells, pericytes, and basement membrane. Although physical exercise is hypothesized to have beneficial effects against AD, it is unknown whether its positive effects extend to ameliorating CAA and improving the physiology of the NVU. We used the triple transgenic animal model for AD (3xTg-AD) at 13 months old and analyzed through behavioral and histological assays, the effect of voluntary physical exercise on cognitive functions, amyloid angiopathy, and the NVU. Our results show that 3xTg-AD mice develop vascular amyloid deposits which correlate with cognitive deficits and NVU alteration. Interestingly, the physical exercise regimen decreases amyloid angiopathy and correlates with an improvement in cognitive function as well as in the underlying integrity of the NVU components. Physical exercise could represent a key therapeutic approach in cerebral amyloid angiopathy and NVU stability in AD patients.

The pathophysiology of rhabdomyolysis in ungulates and rats: towards the development of a rodent model of capture myopathy

Capture myopathy (CM), which is associated with the capture and translocation of wildlife, is a life-threatening condition that causes noteworthy morbidity and mortality in captured animals. Such wildlife deaths have a significant impact on nature conservation efforts and the socio-economic wellbeing of communities reliant on ecotourism. Several strategies are used to minimise the adverse consequences associated with wildlife capture, especially in ungulates, but no successful preventative or curative measures have yet been developed. The primary cause of death in wild animals diagnosed with CM stems from kidney or multiple organ failure as secondary complications to capture-induced rhabdomyolysis. Ergo, the development of accurate and robust model frameworks is vital to improve our understanding of CM. Still, since CM-related complications are borne from biological and behavioural factors that may be unique to wildlife, e.g. skeletal muscle architecture or flighty nature, certain differences between the physiology and stress responses of wildlife and rodents need consideration in such endeavours. Therefore, the purpose of this review is to summarise some of the major etiological and pathological mechanisms of the condition as it is observed in wildlife and what is currently known of CM-like syndromes, i.e. rhabdomyolysis, in laboratory rats. Additionally, we will highlight some key aspects for consideration in the development and application of potential future rodent models.

The unconditioned fear response in dystrophin-deficient mice is associated with adrenal and vascular function

Loss of function mutations in the gene encoding dystrophin elicits a hypersensitive fear response in mice and humans. In the dystrophin-deficient mdx mouse, this behaviour is partially protected by oestrogen, but the mechanistic basis for this protection is unknown. Here, we show that female mdx mice remain normotensive during restraint stress compared to a hypotensive and hypertensive response in male mdx and male/female wildtype mice, respectively. Partial dystrophin expression in female mdx mice (heterozygous) also elicited a hypertensive response. Ovariectomized (OVX) female mdx mice were used to explain the normotensive response to stress. OVX lowered skeletal muscle mass and lowered the adrenal mass and zona glomerulosa area (aldosterone synthesis) in female mdx mice. During a restraint stress, OVX dampened aldosterone synthesis and lowered the corticosterone:11-dehydrocorticosterone. All OVX-induced changes were restored with replacement of oestradiol, except that oestradiol lowered the zona fasciculata area of the adrenal gland, dampened corticosterone synthesis but increased cortisol synthesis. These data suggest that oestrogen partially attenuates the unconditioned fear response in mdx mice via adrenal and vascular function. It also suggests that partial dystrophin restoration in a dystrophin-deficient vertebrate is an effective approach to develop an appropriate hypertensive response to stress.

Voluntary exercise modulates pathways associated with amelioration of retinal degenerative diseases

Background: Exercise has been shown to promote a healthier and longer life and linked to a reduced risk of developing neurodegenerative diseases including retinal degenerations. However, the molecular pathways underpinning exercise-induced cellular protection are not well understood. In this work we aim to profile the molecular changes underlying exercise-induced retinal protection and investigate how exercise-induced inflammatory pathway modulation may slow the progression of retinal degenerations.

Methods: Female C57Bl/6J mice at 6 weeks old were given free access to open voluntary running wheels for a period of 28 days and then subjected to 5 days of photo-oxidative damage (PD)-induced retinal degeneration. Following, retinal function (electroretinography; ERG), morphology (optical coherence tomography; OCT) and measures of cell death (TUNEL) and inflammation (IBA1) were analysed and compared to sedentary controls. To decipher global gene expression changes as a result of voluntary exercise, RNA sequencing and pathway and modular gene co-expression analyses were performed on retinal lysates of exercised and sedentary mice that were subjected to PD, as well as healthy dim-reared controls.

Results: Following 5 days of PD, exercised mice had significantly preserved retinal function, integrity and reduced levels of retinal cell death and inflammation, compared to sedentary controls. In response to voluntary exercise, inflammatory and extracellular matrix integrity pathways were significantly modulated, with the gene expression profile of exercised mice more closely trending towards that of a healthy dim-reared retina.

Conclusion: We suggest that voluntary exercise may mediate retinal protection by influencing key pathways involved in regulating retinal health and shifting the transcriptomic profile to a healthy phenotype.

Running from Stress: Neurobiological Mechanisms of Exercise-Induced Stress Resilience

Chronic stress, even stress of a moderate intensity related to daily life, is widely acknowledged to be a predisposing or precipitating factor in neuropsychiatric diseases. There is a clear relationship between disturbances induced by stressful stimuli, especially long-lasting stimuli, and cognitive deficits in rodent models of affective disorders. Regular physical activity has a positive effect on the central nervous system (CNS) functions, contributes to an improvement in mood and of cognitive abilities (including memory and learning), and is correlated with an increase in the expression of the neurotrophic factors and markers of synaptic plasticity as well as a reduction in the inflammatory factors. Studies published so far show that the energy challenge caused by physical exercise can affect the CNS by improving cellular bioenergetics, stimulating the processes responsible for the removal of damaged organelles and molecules, and attenuating inflammation processes. Regular physical activity brings another important benefit: increased stress robustness. The evidence from animal studies is that a sedentary lifestyle is associated with stress vulnerability, whereas a physically active lifestyle is associated with stress resilience. Here, we have performed a comprehensive PubMed Search Strategy for accomplishing an exhaustive literature review. In this review, we discuss the findings from experimental studies on the molecular and neurobiological mechanisms underlying the impact of exercise on brain resilience. A thorough understanding of the mechanisms underlying the neuroprotective potential of preconditioning exercise and of the role of exercise in stress resilience, among other things, may open further options for prevention and therapy in the treatment of CNS diseases.

Temporal endurance of exercise-induced benefits on hippocampus-dependent memory and synaptic plasticity in female mice

Exercise facilitates hippocampal neurogenesis and neuroplasticity that in turn, promotes cognitive function. Our previous studies have demonstrated that in male mice, voluntary exercise enables hippocampus-dependent learning in conditions that are normally subthreshold for long-term memory formation in sedentary animals. Such cognitive enhancement can be maintained long after exercise has ceased and can be re-engaged by a subsequent subthreshold exercise session, suggesting exercise-induced benefits are temporally dynamic. In females, the extent to which the benefits of exercise can be maintained and the mechanisms underlying this maintenance have yet to be defined. Here, we examined the exercise parameters required to initiate and maintain the benefits of exercise in female C57BL/6J mice. Using a subthreshold version of the hippocampus-dependent task called object-location memory (OLM) task, we show that 14d of voluntary exercise enables learning under subthreshold acquisition conditions in female mice. Following the initial exercise, a 7d sedentary delay results in diminished performance, which can be re-facilitated when animals receive 2d of reactivating exercise following the sedentary delay. Assessment of estrous cycle reveals enhanced wheel running activity during the estrus phase relative to the diestrus phase, whereas estrous phase on training or test had no effect on OLM performance. Utilizing the same exercise parameters, we demonstrate that 14d of exercise enhances long-term potentiation (LTP) in the CA1 region of the hippocampus, an effect that persists throughout the sedentary delay and following the reactivating exercise session. Previous studies have proposed exercise-induced BDNF upregulation as the mechanism underlying exercise-mediated benefits on synaptic plasticity and cognition. However, our assessment of hippocampal Bdnf mRNA expression following memory retrieval reveals no difference between exercise conditions and control, suggesting that persistent Bdnf upregulation may not be required for maintenance of exercise-induced benefits. Together, our data indicate that 14d of voluntary exercise can initiate long-lasting benefits on neuroplasticity and cognitive function in female mice, establishing the first evidence on the temporal endurance of exercise-induced benefits in females.

Exercise on Striatal Dopamine Level and Anxiety-Like Behavior in Male Rats after 2-VO Cerebral Ischemia

The purpose of this study was to discuss the effect of voluntary wheel running on striatal dopamine levels and anxiety-like behavior in rats with global cerebral ischemia. The male Sprague-Dawley rats were signed on in this study and randomly divided into following 4 groups: Control group (C group), Sham group (S group), ischemia group (I group), and 3 weeks physical exercise before ischemia group (3RI group). The rats in the 3RI group were placed in a voluntary running wheel for three weeks to exercise. Then, the rats in I and 3RI groups received bilateral carotid artery ligation (2-VO) operation. The C and S group did not perform voluntary running exercise and the bilateral common carotid arteries of S group were exposed without ligation. In vivo microdialysis was used in conjunction with high performance liquid chromatography (HPLC) and electrochemical detection to ascertain the level of dopamine in the striatum. Elevated plus maze (EPM) and open field (OF) were used to test anxiety status at 24 hours and 7days after 2-VO cerebral ischemia. Meanwhile, gait and motor coordination evaluations were carried out to eliminate the influence of non-specific motor problems. The results indicated that cerebral ischemia instigate the increase of striatal dopamine in I group rats during acute cerebral ischemia. A 3-week voluntary wheel running significantly enhances the striatal dopamine before ischemia and obstructs a further increase of dopamine during acute cerebral ischemia in 3RI group rats. At 24 hours after ischemia, striatal dopamine returned to pre-ischemic levels in 3RI group. Striatal dopamine in I group were less than pre-ischemic levels at 7 days. Behavioral data indicated that 3-week voluntary wheel running promoted recovery of anxiety-like behavior and gait were not affected by 2-VO cerebral ischemia at 24 hours post-ischemia rats. Therefore, it can be concluded that 3-week physical exercise significantly increased the striatal dopamine and improved anxiety-like behavior by inhibiting the increase of dopamine during acute cerebral ischemia and suppressing the decrease of dopamine after 24 hours and 7 days cerebral ischemia.

Voluntary wheel-running activities ameliorate depressive-like behaviors in mouse dry eye models

Recent clinical studies indicate that dry eye is closely associated with psychiatric disorders such as depression and anxiety. Here, we investigated whether two types of mouse dry eye models showed depressive-like behavior in forced swim and sucrose preference tests, and whether voluntary wheel-running helped ameliorate depressive states. To reproduce the dry eye models, the exorbital lacrimal glands (ELG) or exorbital and intraorbital lacrimal glands (ELG+ILG) were bilaterally excised from male C57BL/6J mice. Tear volume was persistently reduced in both models, but the ELG+ILG excision mice exhibited more severe corneal damage than the ELG excision mice. In the forced swim and sucrose preference tests, the gland excision mice showed longer immobility and shorter climbing times, and lower sucrose preference than sham-operated mice, respectively, which appeared earlier in the ELG+ILG excision mice. Wheel-running activities were significantly lower in the ELG+ILG excision mice, but not in the ELG excision mice. After short-period wheel-running, the longer immobility times and the shorter climbing times in the forced swim completely disappeared in both models. Our results suggest that dry eyes might directly cause a depressive disorder that depends on the severity and duration of the ocular surface damage, and that voluntary motor activity could help recovery from a depressive state induced by dry eye.

Molecular Mechanisms of Exercise in Brain Disorders: a Focus on the Function of Brain-Derived Neurotrophic Factor-a Narrative Review

The natural aging process as well as many age-related diseases is associated with impaired metabolic adaptation and declined ability to cope with stress. As major causes of disability and morbidity during the aging process, brain disorders, including psychiatric and neurodegenerative disorders, are likely to increase across the globe in the future decades. This narrative review investigates the link among exercise and brain disorders, aging, and inflammatory biomarkers, along with the function of brain-derived neurotrophic factor. For this study, related manuscript from all databases, Google scholar, Scopus, PubMed, and ISI were assessed. Also, in the search process, the keywords of exercise, neurodegeneration, neurotrophin, mitochondrial dysfunction, and aging were used. Mitochondrial abnormality increases neuronal abnormality and brain disease during the aging process. Stress and inflammatory factors caused by lifestyle and aging also increase brain disorders. Evidences suggest that exercise, as a noninvasive treatment strategy, has antioxidant effects and can reduce neuronal lesions. Brain-derived neurotrophic factor expression following the exercise can reduce brain symptoms; however, careful consideration should be given to a number of factors affecting the results.

Chronic exercise increases excitability of lamina X neurons through enhancement of persistent inward currents and dendritic development in mice

KEY POINTS

Chronic exercise alters adaptability of spinal motor system in rodents. Multiple mechanisms are responsible for the adaptation, including regulation of neuronal excitability and change in dendritic morphology. Spinal interneurons in lamina X are a cluster of heterogeneous neurons playing multifunctional roles in the spinal cord, especially in regulating locomotor activity. Chronic exercise in juvenile mice increased excitability of these interneurons and facilitated dendritic development. Mechanisms underlying these changes remain unknown. Lamina X neurons expressed persistent inward currents (PICs) composed of calcium (Ca-PIC) and sodium (Na-PIC) components. The exercise-increased excitability of lamina X neurons was mediated by enhancing Ca-PIC and Na-PIC components and facilitating dendritic length. Na-PIC contributed more to lowering of PIC onset and Ca-PIC to increase of PIC amplitude. This study unveiled novel morphological and ionic mechanisms underlying adaptation of lamina X neurons in rodents during chronic exercise.

ABSTRACT

Chronic exercise has been shown to enhance excitability of spinal interneurons in rodents. However, the mechanisms underlying this enhancement remain unclear. In this study we investigated adaptability of lamina X neurons with three-week treadmill exercise in mice of P21-P24. Whole-cell path-clamp recording was performed on the interneurons from slices of T12-L4. The experimental results included: (1) Treadmill exercise reduced rheobase by 7.4±2.2 pA (control: 11.3±6.1 pA, n = 12; exercise: 3.8±4.6 pA, n = 13; P = 0.002) and hyperpolarized voltage threshold by 7.1±1.5 mV (control: -36.6±4.6 mV, exercise: -43.7±2.7 mV; P = 0.001). (2) Exercise enhanced persistent inward currents (PICs) with increase of amplitude (control: 140.6±56.3 pA, n = 25; exercise: 225.9±62.5 pA, n = 17; P = 0.001) and hyperpolarization of onset (control: -50.3±3.6 mV, exercise: -56.5±5.5 mV; P = 0.001). (3) PICs consisted of dihydropyridine-sensitive calcium (Ca-PIC) and tetrodotoxin-sensitive sodium (Na-PIC) components. Exercise increased amplitude of both components but hyperpolarized onset of Na-PIC only. (4) Exercise reduced derecruitment current of repetitive firing evoked by current bi-ramp and prolonged firing in falling phase of the bi-ramp. The derecruitment reduction was eliminated by bath application of 3 μM riluzole or 25 μM nimodipine, suggesting that both Na-PIC and Ca-PIC contributed to the exercise-prolonged hysteresis of firing. (5) Exercise facilitated dendritic development with significant increase in dendritic length by 285.1±113 μm (control: 457.8±171.8 μm, n = 12; exercise: 742.9±357 μm, n = 14; P = 0.019). We concluded that three-week treadmill exercise increased excitability of lamina X interneurons through enhancement of PICs and increase of dendritic length. This study provided insight into cellular and channel mechanisms underlying adaptation of the spinal motor system in exercise. Abstract figure legend A. B6 mice were randomly divided into control group and exercise group. Control group mice remained sedentary in the cage; exercise group mice completed 60 min treadmill runs each day (6 days/week) for a period of 3 weeks. B. Whole-cell patch clamp recordings were made from lumbar lamina X neurons after three-weeks exercise. C. Exercise facilitated development of dendrites of lamina X neurons. D. Exercise enhanced persistent inward currents. E. Exercise increased excitability of lamina X neurons by hyperpolarizing voltage threshold for action potential generation. This article is protected by copyright. All rights reserved.

Swimming exercise prevents hippocampal dendritic spine changes and memory loss caused by aging: An application of a new semi-automated spine analysis software

Dendritic spines are small, ratchet-like protrusions on neuronal dendrites that form synapses for receiving neuronal messages. Dendritic spine morphology is associated with synapse function. If neurons degrade or are damaged, the spine morphology of neurons changes. Given that most commercially available spine analysis software is expensive and complex, this study investigated a semi-automated spine analysis software, CTSpine, and used previously published data to verify the accuracy of the analysis results of this software. We also applied CTSpine to understand whether aging causes alterations in the hippocampal spine morphology and whether physical exercise can impede dendritic spine changes in 20 male Sprague Dawley rats. The spines of pyramidal cells in the hippocampal Cornu Ammonis 1 (CA1) region in the aging group were more enriched in filopodium type pattern than those in the control group, whereas the spines of the exercised aging group showed a similar pattern to that of the control. No significant changes were observed in neuronal dendritic spines in other hippocampal regions. However, long-term hippocampal memory was considerably decreased in the aging group, which was reversed to some extent in the exercised aging group. CTSpine, a self-developed semi-automatic spine analysis software, showed results similar to those noted in published data and can be effectively applied to the study of dendritic patterns, including neurodevelopment and disease.

The Effect of Voluntary Physical Activity in an Enriched Environment and Combined Exercise Training on the Satellite Cell Pool in Developing Rats

Aim: Postnatal skeletal muscle growth is strongly associated with a satellite cell pool. Early adolescence might be a crucial period when different exercise training interventions have specific consequence on satellite cells. Pax7 and MyoD have been suggested as the leading indicators of satellite cell activation.

Methods: In this study, pre-adolescent male rats (n = 18) were either subjected to an enriched environment that facilitated physical activities or combined training or control for three weeks. The flexor hallucis longus muscle was removed for biochemical and histochemical analysis.

Results: Findings demonstrated that exercise trained rats displayed high levels of serum IGF-1 (p <0.05). There was an increase in Pax7 (p <0.05) and MyoD (p <0.001) mRNA expression. A significant increase in the mean fiber area (p <0.01), satellite cell (p <0.001), and myonuclear numbers (p <0.01) were also observed in both intervention groups. Importantly, enriched rats showed lower corticosterone levels (p <0.05) compared to training ones. Regarding performance, trained and enriched rats had significant improvement in forelimb grip strength (p <0.01) and load-carrying capacity (p <0.05).

Conclusion: Type of physical exercise is an essential part in changing satellite cells pool. Different and frequent physical activities in an enriched environment can be effective for muscle development.

Aerobic Physical Exercise as a Non-medical Intervention for Brain Dysfunction: State of the Art and Beyond

Brain disorders, including stroke, Alzheimer's disease, depression, and chronic pain, are difficult to effectively treat. These major brain disorders have high incidence and mortality rates in the general population, and seriously affect not only the patient's quality of life, but also increases the burden of social medical care. Aerobic physical exercise is considered an effective adjuvant therapy for preventing and treating major brain disorders. Although the underlying regulatory mechanisms are still unknown, systemic processes may be involved. Here, this review aimed to reveal that aerobic physical exercise improved depression and several brain functions, including cognitive functions, and provided chronic pain relief. We concluded that aerobic physical exercise helps to maintain the regulatory mechanisms of brain homeostasis through anti-inflammatory mechanisms and enhanced synaptic plasticity and inhibition of hippocampal atrophy and neuronal apoptosis. In addition, we also discussed the cross-system mechanisms of aerobic exercise in regulating imbalances in brain function, such as the “bone-brain axis.” Furthermore, our findings provide a scientific basis for the clinical application of aerobic physical exercise in the fight against brain disorders.

Regulation of Voluntary Physical Activity Behavior: A Review of Evidence Involving Dopaminergic Pathways in the Brain

Physical activity leads to well-established health benefits. Current efforts to enhance physical activity have targeted mainly socioeconomic factors. However, despite these efforts, only a small number of adults engage in regular physical activity to the point of meeting current recommendations. Evidence collected in rodent models and humans establish a strong central nervous system component that regulates physical activity behavior. In particular, dopaminergic pathways in the central nervous system are among the best-characterized biological mechanisms to date with respect to regulating reward, motivation, and habit formation, which are critical for establishing regular physical activity. Herein, we discuss evidence for a role of brain dopamine in the regulation of voluntary physical activity behavior based on selective breeding and pharmacological studies in rodents, as well as genetic studies in both rodents and humans. While these studies establish a role of dopamine and associated mechanisms in the brain in the regulation of voluntary physical activity behavior, there is clearly need for more research on the underlying biology involved in motivation for physical activity and the formation of a physical activity habit. Such knowledge at the basic science level may ultimately be translated into better strategies to enhance physical activity levels within the society.

Differential effects of voluntary and forced exercise trainings on spatial learning ability and hippocampal biomarkers in aged female rats

This study aimed to compare the effects of voluntary and forced exercise trainings on cognitive functions and to evaluate their relationship with hippocampal synaptic proteins, neurotrophic factors and markers of oxidative damage in aged female rats. Aged female rats were randomly assigned to control, voluntary exercise training and forced exercise training groups. Voluntary or forced exercise trainings were performed for 12 weeks. At the end of the training period, cognitive functions of the animals were assessed with Morris water maze (MWM) test. After the behavioral test, hippocampus tissues were taken for the analysis of synaptophysin, acetylcholinesterase (AChE), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), malondialdehyde (MDA), protein carbonyl (PC), glutathione (GSH) and superoxide dismutase (SOD). During the MWM test, the number of platform crossings was higher in the voluntary exercise group than in the control group (P < 0.05). In the hippocampus tissue, levels of the synaptophysin, BDNF, NGF and SOD were higher, but MDA levels were lower in the voluntary exercise group than in the control group (P < 0.05). Additionally, hippocampal AChE concentration was higher, but PC levels were lower in the both voluntary and forced exercise groups than in the control group (P < 0.05). In conclusion, voluntary exercise was more effective intervention to improve spatial learning ability in aging process. Increased neurotrophic factors, synaptic proteins, and improved oxidative damage may play a role in these positive effects.

The protective role of exercise against age-related neurodegeneration

Endurance exercise is a widely accessible, low-cost intervention with a variety of benefits to multiple organ systems. Exercise improves multiple indices of physical performance and stimulates pronounced health benefits reducing a range of pathologies including metabolic, cardiovascular, and neurodegenerative disorders. Endurance exercise delays brain aging, preserves memory and cognition, and improves symptoms of neurodegenerative pathologies like Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and various ataxias. Potential mechanisms underlying the beneficial effects of exercise include neuronal survival and plasticity, neurogenesis, epigenetic modifications, angiogenesis, autophagy, and the synthesis and release of neurotrophins and cytokines. In this review, we discuss shared benefits and molecular pathways driving the protective effects of endurance exercise on various neurodegenerative diseases in animal models and in humans.

Prebiotic and Exercise Do Not Alter Knee Osteoarthritis in a Rat Model of Established Obesity

OBJECTIVE

Metabolic disturbance is a known risk factor for cardiovascular disease and has been identified as a risk factor for the development of knee osteoarthritis. In this study, we sought to determine the effects of prebiotic fiber supplementation, aerobic exercise, and the combination of the 2 interventions, on the progression of knee osteoarthritis in a high-fat/high-sucrose diet-induced rat model of metabolic disturbance.

DESIGN

Twelve-week-old male CD-Sprague-Dawley rats were either fed a standard chow diet, or a high-fat/high-sucrose diet. After 12 weeks on diets, rats consuming the high-fat/high-sucrose diet were randomized into 4 subgroups: a sedentary, an aerobic exercise, a prebiotic fiber supplementation, and an aerobic exercise combined with prebiotic fiber supplementation group. The aerobic exercise intervention consisted of a progressive treadmill training program for 12 weeks, while the prebiotic fiber was added to the high-fat/high-sucrose diet at a dose of 10% by weight for 12 weeks. Outcome measures included knee joint damage, body mass, percent body fat, bone mineral density, insulin sensitivity, and serum lipid profile.

RESULTS

Aerobic exercise, or the combination of prebiotic fiber and aerobic exercise, improved select markers of metabolic disturbance, but not knee joint damage. However, these results need to be considered in view of the fact that the chow-fed rats had similar knee OA-like damage as the high-fat/high-sucrose-fed rats.

CONCLUSION

Exercise or prebiotics did not increase joint damage and might be good strategies for populations with metabolic knee osteoarthritis to alleviate other health-related problems, such as diabetes or cardiovascular disorders.

Effects of Simultaneous Exposure to a Western Diet and Wheel-Running Training on Brain Energy Metabolism in Female Rats

BACKGROUND

In the pathogenesis of central nervous system disorders (e.g., neurodegenerative), an important role is attributed to an unhealthy lifestyle affecting brain energy metabolism. Physical activity in the prevention and treatment of lifestyle-related diseases is getting increasing attention.

METHODS

We performed a series of assessments in adult female Long Evans rats subjected to 6 weeks of Western diet feeding and wheel-running training. A control group of lean rats was fed with a standard diet. In all experimental groups, we measured physiological parameters (animal weights, body composition, serum metabolic parameters). We assessed the impact of simultaneous exposure to a Western diet and wheel-running on the cerebrocortical protein expression (global proteomic profiling), and in the second part of the experiment, we measured the cortical levels of protein related to brain metabolism (Western blot).

RESULTS

Western diet led to an obese phenotype and induced changes in the serum metabolic parameters. Wheel-running did not reduce animal weights or fat mass but significantly decreased serum glucose level. The global proteome analysis revealed that the altered proteins were functionally annotated as they were involved mostly in metabolic pathways. Western blot analysis showed the downregulation of the mitochondrial protein-Acyl-CoA dehydrogenase family member 9, hexokinase 1 (HK1)-enzyme involved in principal glucose metabolism pathways and monocarboxylate transporter 2 (MCT2). Wheel-running reversed this decline in the cortical levels of HK1 and MCT2.

CONCLUSION

The cerebrocortical proteome is affected by a combination of physical activity and Western diet in female rats. An analysis of the cortical proteins involved in brain energy metabolism provides a valuable basis for the deeper investigation of changes in the brain structure and function induced by simultaneous exposure to a Western diet and physical activity.

Sensitivity to behavioral stress impacts disease pathogenesis in dystrophin-deficient mice

Mutation to the gene encoding dystrophin can cause Duchenne muscular dystrophy (DMD) and increase the sensitivity to stress in vertebrate species, including the mdx mouse model of DMD. Behavioral stressors can exacerbate some dystrophinopathy phenotypes of mdx skeletal muscle and cause hypotension-induced death. However, we have discovered that a subpopulation of mdx mice present with a wildtype-like response to mild (forced downhill treadmill exercise) and moderate (scruff restraint) behavioral stressors. These "stress-resistant" mdx mice are more physically active, capable of super-activating the hypothalamic-pituitary-adrenal and renin-angiotensin-aldosterone pathways following behavioral stress and they express greater levels of mineralocorticoid and glucocorticoid receptors in striated muscle relative to "stress-sensitive" mdx mice. Stress-resistant mdx mice also presented with a less severe striated muscle histopathology and greater exercise and skeletal muscle oxidative capacity at rest. Most interestingly, female mdx mice were more physically active following behavioral stressors compared to male mdx mice; a response abolished after ovariectomy and rescued with estradiol. We demonstrate that the response to behavioral stress greatly impacts disease severity in mdx mice suggesting the management of stress in patients with DMD be considered as a therapeutic approach to ameliorate disease progression.

Running to save sight: The effects of exercise on retinal health and function

The benefits of exercise to human health have long been recognised. However, only in the past decade have researchers started to discover the molecular benefits that exercise confers, especially to the central nervous system (CNS). These discoveries include the magnitude of molecular messages that are communicated from skeletal muscle to the CNS. Despite these advances in understanding, very limited studies have been conducted to decipher the molecular benefits of exercise in retinal health and disease. Here, we review the latest work on the effects of exercise on the retina and discuss its effects on the wider CNS, with a focus on demonstrating the potential applicability and comparative molecular mechanisms that may be occurring in the retina. This review covers the key molecular pathways where exercise exerts its effects: oxidative stress and mitochondrial health; inflammation; protein aggregation; neuronal health; and tissue crosstalk via extracellular vesicles. Further research on the benefits of exercise to the retina and its molecular messages within extracellular vesicles is highly topical in this field.

Sex Differences in Neurophysiological Changes Following Voluntary Exercise in Adolescent Rats

Background: Adolescence is a period of time characterized by the onset of puberty and is marked by cognitive and social developments and gross physical changes that can play a role in athletic performance. Sex differences are present with differences in body size, height, physiology and behavior which contribute to differences in athletic performance as well. Pre-clinical studies representing this active group are lacking.

Methods: Acute and chronic effects of exercise were evaluated. Male and female adolescent rats were given voluntary access to a running wheel for 10 consecutive days. Running behavior (males and females) and estrous cycling (females only) were analyzed daily. A second group was given 10 days of voluntary access to a running wheel, then rested for 10 days to determine the long-term effects of exercise on the adolescent brain. Brain and muscle tissue were harvested at 10 and 20 day time points to understand exercise-dependent changes in mitochondrial activity and neuroplasticity. Animal cohorts were carried out at two different sites: University of California Los Angeles and Pepperdine University.

Results: On average, running distance, intensity of run, and length of running bout increased for both male and female rats across the 10 days measured. Females ran significantly further and for longer intervals compared to males. Cortical and muscle expression of PGC1α showed similar levels at 10 days regardless of sex and exercise. There was a significant increase in expression at 20 days in all groups correlating with body size (p's < 0.05). Cortical and hippocampal levels of BDNF were similar across all groups, however, BDNF was significantly higher in exercised females at the acute compared to long-term time point.

Discussion: Adolescent rats allowed 10 days of exercise show changes in physiologic function. There are sex differences in running behavior not impacted by sex hormones. These results are important to further our understanding of how exercise impacts the adolescent brain.

The Role of Annexin A1 and Formyl Peptide Receptor 2/3 Signaling in Chronic Corticosterone-Induced Depression-Like behaviors and Impairment in Hippocampal-Dependent Memory

BACKGROUND

The activity of the Hypothalamic-Pituitary-Adrenal (HPA) axis is commonly dysregulated in stress-related psychiatric disorders. Annexin A1 (ANXA1), an endogenous ligand of Formyl Peptide Receptor (FPR) 2/3, is a member of the family of phospholipid- and calcium-binding proteins with a well-defined role in the delayed early inhibitory feedback of Glucocorticoids (GC) in the pituitary gland and implicated in the occurrence of behavioural disorders such as anxiety.

OBJECTIVE

The present study aimed to evaluate the potential role of ANXA1 and its main receptor, as a cellular mediator of behavioural disorders, in a model of Corticosterone (CORT)-induced depression and subsequently, the possible correlation between the depressive state and impairment of hippocampal memory.

METHODS

To induce the depression model, Wild-Type (WT), ANXA1 Knockout (KO), and FPR2/3 KO mice were exposed to oral administration of CORT for 28 days dissolved in drinking water. Following this, histological, biochemical and behavioural analyses were performed.

RESULTS

FPR2/3 KO and ANXA1 KO mice showed improvement in anxiety and depression-like behaviour compared with WT mice after CORT administration. In addition, FPR2/3 KO and ANXA1 KO mice showed a reduction in histological alterations and neuronal death in hippocampal sections. Moreover, CORT+ FPR2/3 KO and ANXA1 KO, exhibited a higher expression of Brain-Derived Neurotrophic Factor (BDNF), phospho-ERK, cAMP response element-binding protein (pCREB) and a decrease in Serotonin Transporter Expression (SERT) compared to WT(CORT+) mice.

CONCLUSION

In conclusion, the absence of the ANXA1 protein, even more than the absence of its main receptor (FPR 2/3), was fundamental to the inhibitory action of GC on the HPA axis; it also maintained the hippocampal homeostasis by preventing neuronal damage associated with depression.

Two weeks of moderate intensity locomotor training increased corticosterone concentrations but did not alter the number of adropin-immunoreactive cells in the hippocampus of diabetic type 2 and control rats

Adropin (ADR) plays a role in metabolism regulation and its alterations in obesity and diabetes have been found. Treatment with ADR was beneficial in metabolic diseases, and physical exercise increased ADR concentrations in obese patients. However, data on the distribution of ADR in the brain are sparse. The role of metabolic status and physical exercise on its expression in the brain is undiscovered. We hypothesized that diabetes type 2 (DM2) and/or exercise will alter number of ADR-immunoractive (-ir) cells in the rat brain. Animals were divided into groups: diabetes type 2 (receiving high-fat diet and injections of streptozotocin) and control (fed laboratory chow diet; C). Rats were further divided into: running group (2 weeks of forced exercise on a treadmill) and non-running group. Body mass, metabolic and hormonal profiles were assessed. Immunohistochemistry was run to study ADR-ir cells in the brain. We found that: 1) in DM2 animals, running decreased insulin and increased glucose concentrations; 2) in C rats, running decreased insulin concentrations and had no effect on glucose concentration in blood; 3) running increased corticosterone (CORT) concentrations in DM2 and C rats; 4) ADR-ir cells were detected in the hippocampus and ADR-ir fibers in the arcuate nucleus of the hypothalamus, which is a novel location; 5) metabolic status and running, however, did not change number of these cells. We concluded that 2 weeks of forced moderate intensity locomotor training induced stress response present as increased concentration of CORT and did not influence number of ADR-ir cells in the brain.

Moderate Intensity Treadmill Exercise Increases Survival of Newborn Hippocampal Neurons and Improves Neurobehavioral Outcomes after Traumatic Brain Injury

Physician-prescribed rest after traumatic brain injury (TBI) is both commonplace and an increasingly scrutinized approach to TBI treatment. Although this practice remains a standard of patient care for TBI, research of patient outcomes reveals little to no benefit of prescribed rest after TBI, and in some cases prolonged rest has been shown to interfere with patient well-being. In direct contrast to the clinical advice regarding physical activity after TBI, animal models of brain injury consistently indicate that exercise is neuroprotective and promotes recovery. Here, we assessed the effect of low and moderate intensity treadmill exercise on functional outcome and hippocampal neural proliferation after brain injury. Using the controlled cortical impact (CCI) mouse model of TBI, we show that 10 days of moderate intensity treadmill exercise initiated after CCI reduces anxiety-like behavior, improves hippocampus-dependent spatial memory, and promotes hippocampal proliferation and newborn neuronal survival. Pathophysiological measures including lesion volume and axon degeneration were not altered by exercise. Taken together, these data reveal that carefully titrated physical activity may be a safe and effective approach to promoting recovery after brain injury.

Voluntary wheel running with and without follistatin overexpression improves NMJ transmission but not motor unit loss in late life of C57BL/6J mice

Sarcopenia, or pathological loss of muscle mass and strength during aging, is an important contributor to loss of physical function in older adults. Sarcopenia is a multifactorial syndrome associated with intrinsic muscle and upstream neurological dysfunction. Exercise is well-established as an effective intervention for sarcopenia, but less is known about the long-term neurobiological impact of exercise. The goals of this study were to investigate the effects of exercise, alone or in combination with follistatin (FST) overexpression (antagonist of myostatin), on neuromuscular junction transmission and motor unit numbers in mice between the age of 22 and 27 months, ages at which prior studies have demonstrated that some motor unit loss is already evident. C57BL/6J mice underwent baseline assessment and were randomized to housing with or without voluntary running wheels and injection with adeno-associated virus to overexpress FST or vehicle. Groups for comparison included sedentary and running with and without FST. Longitudinal assessments showed significantly increased muscle mass and contractility in the 'running plus FST' group, but running, with and without FST, showed no effect on motor unit degeneration. In contrast, running, with and without FST, demonstrated marked improvement of neuromuscular junction transmission stability.

Homeostatic state of microglia in a rat model of chronic sleep restriction

Chronic sleep restriction (CSR) negatively impacts brain functions. Whether microglia, the brain's resident immune cells, play any role is unknown. We studied microglia responses to CSR using a rat model featuring slowly rotating wheels (3 h on/1 h off), which was previously shown to induce both homeostatic and adaptive responses in sleep and attention. Adult male rats were sleep restricted for 27 or 99 h. Control rats were housed in locked wheels. After 27 and/or 99 h of CSR, the number of cells immunoreactive for the microglia marker ionized calcium-binding adaptor molecule-1 (Iba1) and the density of Iba1 immunoreactivity were increased in 4/10 brain regions involved in sleep/wake regulation and cognition, including the prelimbic cortex, central amygdala, perifornical lateral hypothalamic area, and dorsal raphe nucleus. CSR neither induced mitosis in microglia (assessed with bromodeoxyuridine) nor impaired blood-brain barrier permeability (assessed with Evans Blue). Microglia appeared ramified in all treatment groups and, when examined quantitatively in the prelimbic cortex, their morphology was not affected by CSR. After 27 h, but not 99 h, of CSR, mRNA levels of the anti-inflammatory cytokine interleukin-10 were increased in the frontal cortex. Pro-inflammatory cytokine mRNA levels (tumor necrosis factor-α, interleukin-1β, and interleukin-6) were unchanged. Furthermore, cortical microglia were not immunoreactive for several pro- and anti-inflammatory markers tested, but were immunoreactive for the purinergic P2Y12 receptor. These results suggest that microglia respond to CSR while remaining in a physiological state and may contribute to the previously reported homeostatic and adaptive responses to CSR.

The downstream effects of forced exercise training and voluntary physical activity in an enriched environment on hippocampal plasticity in preadolescent rats

During critical periods of brain development, exercise-induced physical fitness may greatly impact the brain structure and function. Nevertheless, forced and intensive physical activities may display negative effects, particularly in the pre-pubertal period. Preadolescent rats were exposed to an enriched environment and combined exercise training for three consecutive weeks in the present study. There was a large cage with enriching stimuli and voluntary physical activity opportunities as an enriched environment (EE). The combined exercise training (CET) consisted of aerobic and resistance training programs. The protein levels of corticosterone (CORT), glucocorticoid receptors (GR_s), insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) were assessed using Enzyme-linked immunosorbent assay and western blotting. Cresyl violet staining was also used to evaluate the number of cells in the hippocampus. While GR_s levels were significantly increased in both EE and CET groups (P < 0.001), decreased CORT levels were found in enriched rats (P < 0.05). Moreover, elevated BDNF levels were found in the EE (P < 0.01) and CET (P < 0.05) groups. Similarly, VEGF significantly increased in the EE (P < 0.01) and CET (P < 0.05) animals. However, IGF-1 levels were high only in trained rats (P < 0.05). The number of cells also significantly increased in the DG and CA1 region of the hippocampus after each intervention (P < 0.001). These findings clarified that combined exercise training and voluntary physical activity in an enriched environment during the preadolescent period might promote the downstream plasticity effects on the hippocampus.

Comparison of murine behavioural and physiological responses after forced exercise by electrical shock versus manual prodding

NEW FINDINGS

What is the central question of this study? Forced treadmill exercise using electrical shock is the most common technique in rodent exercise studies. Here, we examined how the use of electrical shock during forced treadmill exercise affects behavioural and physiological responses in comparison to a novel non-electrical shock technique. What is the main finding and its importance? In comparison to mice that underwent traditional treadmill running induced by electrical shock, mice that underwent forced running using a novel technique involving gentle prodding to induce running showed: (i) higher locomotor activity; (ii) less anxiety-like behaviour; and (iii) altered exercise-induced muscle pain immediately after exercise.

ABSTRACT

Animal models of exercise have been useful to understand underlying cellular and molecular mechanisms. Many studies have used methods of exercise that are unduly stressful (e.g., electrical shock to force running), potentially skewing results. Here, we compared physiological and behavioural responses of mice after exercise induced using a prodding technique that avoids electrical shock versus a traditional protocol using electrical shock. We found that exercise performance was similar for both techniques; however, the shock group demonstrated significantly lower locomotor activity and higher anxiety-like behaviour. We also observed divergent effects on muscle pain; the prodding group showed hyperalgesia immediately after exercise, whereas the shock group showed hypoalgesia. Corticosterone concentrations were elevated to a similar extent for both groups. In conclusion, mice that were exercised without shock generated similar maximal exercise performance, but postexercise these mice showed an increase in locomotor activity, less anxiety-like behaviour and altered muscle pain in comparison to mice that exercised with shock. Our data suggest that running of mice without the use of electrical shock is potentially less stressful and might be a better technique to study the physiological and behavioural responses to exercise.

Effects of voluntary and forced exercises on motor function recovery in intracerebral hemorrhage rats

Motor paralysis is a severe consequence of intracerebral hemorrhage (ICH) that reduces patient quality of life. Rehabilitation is beneficial for stroke patients. However, functional recovery depends on the exercise type, and which factors are effective during rehabilitation are unknown. We aimed to clarify the effect of voluntary and forced exercises for functional recovery in ICH rats. Male Sprague-Dawley rats were divided into three groups: forced treadmill running (F-Ex.), voluntary wheel cage running (V-Ex.) and no exercise (Non-Ex.). The effects of the two exercises on motor recovery were analyzed by determining the motor deficit score and using the beam walking test. Stress and motivation status after rehabilitation were determined by corticosterone concentrations (ELISA) and immunoreactivity of ΔFosB (immunohistochemistry) in the nucleus accumbens, respectively. Significantly enhanced motor functional recovery was observed in the two trained groups compared with that in the Non-Ex. group. Of note, recovery in the V-Ex. group was greater than that in the F-Ex. group. To investigate the motivation and stress related to the exercises, the expression of ΔFosB in the nucleus accumbens and corticosterone concentration were compared after rehabilitation. In the V-Ex. group, there was a significant increase of ΔFosB, and in the F-Ex. Group, there was a high concentration of corticosterone. These data suggest that the effect of training for motor recovery was enhanced by motivation and reduced by stress.

The positive effects of running exercise on hippocampal astrocytes in a rat model of depression

Running exercise has been shown to alleviate depressive symptoms, but the mechanism of its antidepressant effect is still unclear. Astrocytes are the predominant cell type in the brain and perform key functions vital to central nervous system (CNS) physiology. Mounting evidence suggests that changes in astrocyte number in the hippocampus are closely associated with depression. However, the effects of running exercise on astrocytes in the hippocampus of depression have not been investigated. Here, adult male rats were subjected to chronic unpredictable stress (CUS) for 5 weeks followed by treadmill running for 6 weeks. The sucrose preference test (SPT) was used to assess anhedonia of rats. Then, immunohistochemistry and modern stereological methods were used to precisely quantify the total number of glial fibrillary acidic protein (GFAP)⁺ astrocytes in each hippocampal subregion, and immunofluorescence was used to quantify the density of bromodeoxyuridine (BrdU)⁺ and GFAP⁺ cells in each hippocampal subregion. We found that running exercise alleviated CUS-induced deficit in sucrose preference and hippocampal volume decline, and that CUS intervention significantly reduced the number of GFAP⁺ cells and the density of BrdU⁺/GFAP⁺ cells in the hippocampal CA1 region and dentate gyrus (DG), while 6 weeks of running exercise reversed these decreases. These results further confirmed that running exercise alleviates depressive symptoms and protects hippocampal astrocytes in depressed rats. These findings suggested that the positive effects of running exercise on astrocytes and the generation of new astrocytes in the hippocampus might be important structural bases for the antidepressant effects of running exercise.

Interaction between intensity and duration of acute exercise on neuronal activity associated with depression-related behavior in rats

We examined the activities of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) and corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) during acute treadmill running at different speeds (control, low, high) and durations (15, 30, 60 min) in male Wistar rats using c-Fos/5-HT or CRF immunohistochemistry. We also performed elevated plus maze test (EPM) and forced swim test (FST) after acute treadmill running in rats. Acute treadmill running at low speed, regardless of exercise duration, significantly increased c-Fos expression in 5-HT neurons in the DRN compared with controls, whereas high-speed running significantly activated 5-HT neurons only at 60-min duration. In contrast, c-Fos expression in CRF neurons in the PVN was enhanced in an intensity-dependent manner, regardless of exercise duration. c-Fos expression in 5-HT neurons in the DRN induced by the acute treadmill running for 30 or 60 min, but not 15 min, was positively correlated with the time spent on the open arms in the EPM and was negatively correlated with the immobility time in the FST. These results suggest an interaction between exercise intensity and duration on the antidepressant effects of acute physical exercise.

Difference in the brain serotonin and its metabolite level and anxiety-like behavior between forced and voluntary exercise conditions in rats

Physical exercise is beneficial to both physical and mental health, though it is unclear whether voluntary and forced exercise have the same effects. We investigated the effects of chronic forced and voluntary wheel running on brain levels of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), and anxiety-like behavioral change in rats. Forty-eight rats were randomly assigned to standard cages (sedentary control: SC); voluntary exercise (free running on a wheel, V-EX); voluntary limited exercise (wheel available only 1 h per day, VL-EX); and forced exercise (running on a motorized wheel, F-EX). After 4 weeks, rats either underwent the open field test (OFT) or their 5-HT and 5-HIAA levels were measured in the major serotonergic neural cell bodies and projection areas. 5-HT and 5-HIAA levels in the dorsal and median raphe nuclei were increased in the V-EX, but not in the VL-EX and F-EX groups, compared with the SC group. In the paraventricular hypothalamic nucleus and caudate putamen, only 5-HT levels were increased in the V-EX group. Interestingly, in the amygdala, only 5-HIAA levels were significantly increased in the V-EX group. Conversely, we found that F-EX rats showed no significant 5-HT changes and increased anxiety-like behavior. VL-EX did not have significant beneficial effects on any of the experimental parameters. These data suggest that only unlimited voluntary exercise stimulates the serotonergic system and suppresses anxiety-like behavior.

Association between brain morphometry and aerobic fitness level and sex in healthy emerging adults

OBJECTIVE

Aerobic fitness may be beneficial for neuroanatomical structure. However, few have investigated this in emerging adults while also accounting for potential sex differences. Here we examine aerobic fitness level, sex, and their interaction in relation to cortical thickness, surface area, and volume.

METHOD

Sixty-three young adults between the ages of 16-26 were balanced for sex and demonstrated a wide range of aerobic fitness levels. Exclusion criteria included left-handedness, past-year independent Axis-I disorders, major medical/neurologic disorders, prenatal medical issues, prenatal alcohol/illicit drug exposure, or excessive substance use. Participants completed an MRI scan and a graded exercise test to volitional fatigue (VO2 max). Data analyses were run in Freesurfer and data was corrected for multiple comparisons with Monte Carlo simulations at .05.

RESULTS

Males demonstrated higher VO2 values. Higher VO2 values were statistically independently related to thinner lateral occipital, superior parietal, cuneus, precuneus, and inferior parietal regions, smaller lateral occipital volume, and larger inferior parietal surface area. Compared to females, males had larger volume in rostral anterior cingulate, lateral occipital, and superior frontal regions, and greater surface area in fusiform, inferior parietal, rostral and caudal anterior cingulate, and superior parietal regions. VO2*Sex interactions revealed higher-fit females had higher inferior parietal, paracentral, and supramarginal surface area, while lower-fit males showed larger surface area in these same regions.

CONCLUSIONS

Individuals with higher aerobic fitness performance had thinner cortices, lower volume, and larger surface area in sensorimotor regions than lower fit individuals, perhaps suggesting earlier neuromaturation in higher fit individuals. Larger surface area was associated with higher-fit females and lower-fit males. Thus both sex and aerobic fitness are important in shaping brain health in emerging adults.

Nuclear Factor [Erythroid-derived 2]-like 2 and Mitochondrial Transcription Factor A Contribute to Moderate-intensity Swimming Effectiveness against Memory Impairment in Young Mice Induced by Concomitant Exposure to a High-calorie Diet during the Early Life Period

Increased energy food consumption during early-life has been associated with memory impairment. Swimming training has been reported to improve memory processes in rodent models. This study aimed to evaluate whether moderate-intensity swimming training counteracts learning and memory impairment in young mice fed a high-calorie diet during the early-life period. The contribution of hippocampal oxidative stress, as well as nuclear factor [erythroid-derived 2]-like 2/Kelch-like ECH-associated protein (NRF2/Keap-1/HO-1) and peroxisome proliferator-activated receptor gamma co-activator 1-alpha/mitochondrial transcription factor A (PCG-1α/mtTFA) signaling, in memory effects was also investigated. Three-week-old male Swiss mice received a high-calorie diet (20% fat; 20% carbohydrate enriched) or a standard diet from 21 to 49 postnatal days. Mice performed a moderate-intensity swimming protocol (5 days/week) and behavioral tests predictive of memory function. Mice fed a high-calorie diet and subjected to the swimming protocol performed better on short- and long-term spatial and object recognition memory tests than those fed a high-calorie diet. The swimming protocol modulated the hippocampal NRF2/Keap-1/HO-1 and mtTFA pathways in mice fed a high-calorie diet. Swimming training positively affected location and long-term memory, fat mass content, as well as NRF2/Keap-1/HO-1 and mtTFA proteins of control-diet-fed mice. In conclusion, a moderate-intensity swimming training evoked an adaptive response in mice fed a high-calorie diet by restoring different types of memory-impaired and hippocampal oxidative stress as well as upregulated the NRF2/Keap-1/HO-1 and mtTFA pathways.