Exercise, learned helplessness, and the stress-resistant brain

Effects of swimming exercise on neuropathic pain in a rat model: role of glutamate

OBJECTIVE

The pain-reducing effects of the exercise were exerted through different mechanisms. Knowing more clear mechanisms helps to find more approach that is therapeutic. The objective of the present study is the evaluation of cerebrospinal fluid (CSF) glutamate level alteration in neuropathic pain rats and whether physical activity could modulate it.

METHODS

In the present study 104 male Wistar rats weighing 180-220 g were randomly divided into 4 groups (Sham, Sham + Exe, Neuropathy, and Neuropathy + Exe) which in turn each group subdivided into 4 groups according to time points for behavioral testing and CSF sampling (Baseline, 2 weeks, 3 weeks, and 4 weeks). To induction of neuropathy (by chronic constriction injury,), after anesthetizing with a mixture of ketamine (80 mg/kg) and xylazine (10 mg/kg), the animal's right sciatic nerve was exposed and was ligated using four movable catgut chromic suture 4/0. The exercise protocol included 25 min of daily swimming, 5 days a week for 4 weeks. Thermal hyperalgesia and mechanical tactile threshold were detected using the plantar test and Von Frey filaments, respectively. CSF glutamate level was determined using high-performance liquid chromatography.

RESULTS

Findings indicated that mechanical and thermal thresholds significantly (p < 0.01, p < 0.05 respectively) decreased in the neuropathy group against that in sham groups. On the other hand, exercise significantly increased mechanical tactile threshold (p < 0.0012) and thermal threshold (p < 0.05) compared to the neuropathy group. Moreover, CSF glutamate level prominently (p < 0.01) was increased in the neuropathy group compared to the sham group, and swimming exercise significantly (p < 0.001) reduced it.

IN CONCLUSION

The present findings provide new evidence showing that medium-intensity swimming exercise attenuates pain-like behaviors in neuropathic pain animals, which is possibly due to decreasing CSF glutamate level and its neurotransmission.

[Sports and Physical Exercise Therapy in the Treatment of Mental Health Issues in Children and Adolescents]

Sports and Physical Exercise Therapy in the Treatment of Mental Health Issues in Children and Adolescents Abstract: Mental disorders are among the most common chronic diseases in childhood and adolescence in Germany and worldwide. The health benefits of a physically active lifestyle during adolescence are well documented. Furthermore, a growing body of evidence suggests a positive impact of physical activity on mental health and emotional well-being. Longitudinal studies also show an association between physical activity and reduced risk of developing a mental disorder. Therefore, therapeutic exercise plays an important role in child and adolescent psychiatry. High-quality randomized-controlled trials are needed to substantiate the described effects.

Effect of Training for an Athletic Challenge on Illness Cognition in Individuals with Chronic Disability: A Prospective Cohort Study

Illness cognitions (IC) influence how a patient adapts to a chronic disease. The aim was (1) to determine if training for a handcycling mountain time trial (HandbikeBattle) improves IC and (2) to identify factors associated with IC change scores. Persons with a chronic disability (N = 220; including N = 151 with spinal cord disorder) trained 5 months and participated in the time trial. The IC Questionnaire measured helplessness, acceptance, perceived benefits and was assessed before training (T1), after training (T2), and four months after the event (T3). Age, sex, body mass index (BMI), time since injury (TSI), disability characteristics, self-efficacy, mental health (MH) and musculoskeletal pain were obtained at T1. Multilevel regression analyses showed that helplessness decreased (from 11.96 to 11.28, p < 0.01) and perceived benefits increased (from 16.91 to 17.58, p < 0.01) from T1 to T2. For helplessness this decrease persisted during follow-up (11.16 at T3). Changes in helplessness were associated with self-efficacy (p = 0.02), MH (p = 0.02) and lesion completeness (p = 0.02), and were independent of disability type (p = 0.66), lesion level (p = 0.30) and demographics such as sex (p = 0.29) and age (p = 0.67). Training with peers may improve helplessness and perceived benefits in individuals with a chronic disability. Especially individuals with MH problems might benefit from training for an athletic challenge with peers to improve illness cognitions, and ultimately, quality of life.

Treadmill Exercise Improves Behavioral and Neurobiological Alterations in Restraint-Stressed Rats

Stress is a state that is known to impact an organism's physiological and psychological balance as well as the morphology and functionality of certain brain areas. In the present work, chronic restraint stress (CRS) model rats treated with treadmill exercise were used to examine anomalies associated to emotion and mood as well as molecular changes in the brain. Forty male Sprague-Dawley rats were divided into control, stress, exercise, and stress+exercise groups. CRS were exposed to stress group rats and exercise group underwent a chronic treadmill exercise. Depressive-like behavior was evaluated with the forced swim test (FST) and tail suspension test (TST). For assessing anxiety-like behavior, the light-dark test (LDT) and the open field test (OFT) were used. The Morris water maze test (MWMT) was used for testing memory and learning. Brain's monoamine level and the expression of genes related to stress were measured. It was discovered that CRS lengthens latency in the MWMT, increases immobility in the FST and TST, decreases time in the light compartment, and causes hypoactivity in the OFT. CRS reduced the dopamine levels in the nucleus accumbens(NAc). Brain-derived neurotrophic factor (BDNF), dopamine receptors, and serotonin receptor (HTR2A) gene expression in the prefrontal cortex, corpus striatum, and hypothalamus were decreased by CRS. Exercise on a treadmill leads to increase NAc's dopamine and noradrenaline levels and prevented behavioral alterations. Exercise increased the alterations of BDNF expressions in the brain in addition to improving behavior. As a result, CRS-induced behavioral impairments were effectively reversed by chronic treadmill exercise with molecular alterations in the brain.

Comparing the efficacy of different types of exercise for the treatment and prevention of depression in youths: a systematic review and network meta-analysis

Purpose

Depression disorder is the most commonly diagnosed type of mental illness among youths. Although a plethora of evidence suggests a positive relationship between exercise and lower levels of depression in youths, the findings regarding the variation in magnitude of this relationship are inconclusive with respect to the preventive and therapeutic effects of different types of exercise. This network meta-analysis aimed to determine the best type of exercise for the treatment and prevention of depression in youths.

Methods

A comprehensive search of databases, including PubMed, EMBASE, The Cochrane Library, Web of Science, PsychINFO, ProQuest, Wanfang, and CNKI, was conducted to identify relevant research on exercise interventions for depression in youth populations. The risk of bias in the included studies was evaluated using Cochrane Review Manager 5.4 according to the Cochrane Handbook 5.1.0 Methodological Quality Evaluation Criteria. The network meta-analysis was performed using STATA 15.1 to calculate the standardized mean difference (SMD) of all concerned outcomes. The node-splitting method was used to test the local inconsistency of the network meta-analysis. Funnel plots were used to evaluate the potential impact of bias in this study.

Result

Utilizing data extracted from 58 studies (10 countries, 4,887 participants), we found that for depressed youths, exercise is significantly better than usual care in reducing anxiety (SMD = -0.98, 95% CI [-1.50, -0.45]). For non-depressed youths, exercise is significantly better than usual care in reducing anxiety (SMD = -0.47, 95% CI [ -0.66, -0.29]). In the treatment of depression, resistance exercise (SMD = -1.30, 95% CI [ -1.96, -0.64]), aerobic exercise (SMD = -0.83, 95% CI [-1.10 -0.72]), mixed exercise (SMD = -0.67, 95% CI [-0.99, -0.35]), and mind-body exercise (SMD = -0.61, 95% CI [-0.84, -0.38]) all showed significant efficacy over usual care. For the prevention of depression, resistance exercise (SMD = -1.18, 95% CI [-1.65, -0.71]), aerobic exercise (SMD = -0.72, 95% CI [-0.98, -0.47]), mind-body exercise (SMD = -0.59, 95% CI [-0.93, -0.26]), and mixed exercise (SMD = -1.06, 95% CI [-1.37 to -0.75]) were all significantly effective compared to usual care. According to the test of the surface under the cumulative ranking score (SUCRA), the ranking of exercises for the treatment of depression in depressed youths is as follows: resistance exercise (94.9%) > aerobic exercise (75.1%) > mixed exercise (43.8%) > mind-body exercise (36.2%) > usual care (0%). For the prevention of depression in non-depressed youths, resistance exercise (90.3%) > mixed exercise (81.6%) > aerobic exercise (45.5%) > mind-body exercise (32.6%) > usual care (0%). Resistance exercise thus had the best comprehensive effect on both the treatment and prevention of depression in youths (clusterank value = 1914.04). Subgroup analyses show that a frequency of 3-4 times per week, a duration of 30-60 min, and a length of more than 6 weeks were found to be the most effective interventions for depression (P > 0.001).

Conclusion

This study provides compelling evidence that exercise is a viable intervention for improving depression and anxiety in young individuals. In addition, the study emphasizes the importance of selecting the appropriate type of exercise to optimize treatment and prevention. Specifically, the results suggest that resistance exercise, performed 3-4 times per week, with sessions lasting 30-60 min and a length of more than 6 weeks, yields optimal results for the treatment and prevention of depression in young individuals. These findings have significant implications for clinical practice, particularly given the challenges associated with implementing effective interventions and the economic burden of treating and preventing depression in young people. However, it is worth noting that additional head-to-head studies are necessary to confirm these findings and strengthen the evidence base. Nevertheless, this study provides valuable insights into the role of exercise as a potential treatment and preventative measure for depression in young people.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=374154, identifier: 374154.

Academic Helplessness and Life Satisfaction in Korean Adolescents: The Moderated Mediation Effects of Leisure Time Physical Activity

This study examined whether depression mediates a relationship between academic helplessness and life satisfaction and whether the mediating effect differs depending on participation in leisure time physical activity (LTPA) from a sample of 2384 middle school students in South Korea. Identifying these factors could help in developing intervention strategies for promoting life satisfaction. Structural equation modeling analyses were employed to understand how various factors influence adolescents' life satisfaction. First, the effect of academic helplessness on life satisfaction was mediated by depression. Second, the mediating effect of depression was moderated according to participation in LTPA: the size of the negative mediating effect of depression on the relationship between academic helplessness and life satisfaction was reduced in the LTPA group compared to the non-LTPA group. The current findings suggest that encouraging engagement in physical activity may be a crucial vehicle for affecting academic helplessness, depression, and life satisfaction among early adolescents. Implications and future directions are discussed.

Examining the Effect of Increased Aerobic Exercise in Moderately Fit Adults on Psychological State and Cognitive Function

Regular physical exercise can decrease the risk for obesity, diabetes, and cardiovascular disease, increase life expectancy, and promote psychological health and neurocognitive functioning. Cross-sectional studies show that cardiorespiratory fitness level (VO2 max) is associated with enhanced brain health, including improved mood state and heightened cognitive performance. Interventional studies are consistent with these cross-sectional studies, but most have focused on low-fit populations. Few such studies have asked if increasing levels of physical activity in moderately fit people can significantly enhance mood, motivation, and cognition. Therefore, the current study investigated the effects of increasing aerobic exercise in moderately fit individuals on psychological state and cognitive performance. We randomly assigned moderately fit healthy adults, 25-59 years of age, who were engaged in one or two aerobic exercise sessions per week to either maintain their exercise regimen (n = 41) or increase their exercise regimen (i.e., 4-7 aerobic workouts per week; n = 39) for a duration of 3 months. Both before and after the intervention, we assessed aerobic capacity using a modified cardiorespiratory fitness test, and hippocampal functioning via various neuropsychological assessments including a spatial navigation task and the Mnemonic Similarity Task as well as self-reported measures including the Positive and Negative Affect Scale, Beck Anxiety Inventory, State-Trait Anxiety Inventory, Perceived Stress Scale, Rumination Scale, Eating Disorders Examination, Eating Attitudes Test, Body Attitudes Test, and Behavioral Regulation of Exercise Questionnaire. Consistent with our initial working hypotheses, we found that increasing exercise significantly decreased measures of negative affect, including fear, sadness, guilt, and hostility, as well as improved body image. Further, we found that the total number of workouts was significantly associated with improved spatial navigation abilities and body image as well as reduced anxiety, general negative affect, fear, sadness, hostility, rumination, and disordered eating. In addition, increases in fitness levels were significantly associated with improved episodic memory and exercise motivation as well as decreased stress and disordered eating. Our findings are some of the first to indicate that in middle-aged moderately-fit adults, continuing to increase exercise levels in an already ongoing fitness regimen is associated with additional benefits for both psychological and cognitive health.

Voluntary Wheel Running Reduces Vesicle Development in an Endometriosis Animal Model Through Modulation of Immune Parameters

Introduction

Endometriosis is a chronic gynecological disorder characterized by the growth of endometrial glands and stroma outside the endometrial cavity producing inflammation and pain. Previously we demonstrated that modulation of the hypothalamic pituitary adrenal (HPA) axis exacerbates the development and severity of this condition. A physically active lifestyle has been shown to confer health benefits in many chronic conditions by potentially acting as a stress buffer, thus we hypothesized that voluntary physical exercise can “realign/reset” the HPA axis resulting in reduced endometriosis symptoms in an animal model.

Methods

Endometriosis was induced in female Sprague Dawley rats by implanting uterine tissue next to the intestinal mesentery on day 0. Sham controls received sutures only. One group of endometriosis animals had access to a running wheel for 2 weeks prior to endometriosis induction until time of sacrifice at day 60. Sham and endometriosis controls received no exercise. All animals were examined for developed vesicles which were collected and measured. Uterine tissue was analyzed for cellular infiltration. Brain, liver, spleen, adrenal glands, leg muscles, and fat were collected, along with peritoneal fluid and blood.

Results

Endometriosis animals developed vesicles in 86.96% of the implants with significantly increased mesenteric fat compared to sham (p < 0.05). Exposure to exercise significantly decreased the size (p < 0.01) and number (p < 0.05) of vesicles that developed, as well as the mesenteric fat (p < 0.01). Exercised animals had higher levels of lactoferrin in peritoneal fluid, and decreased serum fractalkine and leptin. Exercise significantly increased estrogen alpha receptor expression levels (p < 0.01), while significantly decreasing estrogen receptor beta expression (p < 0.01) and macrophage infiltration (p < 0.05) in vesicles compared to non- exercised animals.

Conclusions

Our results suggest that voluntary physical activity might protect against endometriosis and alleviate the associated inflammation via immune modulation of the HPA axis. This offers the potential for further exploration of exercise as a complementary therapy in endometriosis patients.

Environmental certainty influences the neural systems regulating responses to threat and stress

Flexible calibration of threat responding in accordance with the environment is an adaptive process that allows an animal to avoid harm while also maintaining engagement of other goal-directed actions. This calibration process, referred to as threat response regulation, requires an animal to calculate the probability that a given encounter will result in a threat so they can respond accordingly. Here we review the neural correlates of two highly studied forms of threat response suppression: extinction and safety conditioning. We focus on how relative levels of certainty or uncertainty in the surrounding environment alter the acquisition and application of these processes. We also discuss evidence indicating altered threat response regulation following stress exposure, including enhanced fear conditioning, and disrupted extinction and safety conditioning. To conclude, we discuss research using an animal model of coping that examines the impact of stressor controllability on threat responding, highlighting the potential for previous experiences with control, or other forms of coping, to protect against the effects of future adversity.

Blood-Brain Barrier Dysfunction in the Pathogenesis of Major Depressive Disorder

Major depression represents a complex and prevalent psychological disease that is characterized by persistent depressed mood, impaired cognitive function and complicated pathophysiological and neuroendocrine alterations. Despite the multifactorial etiology of depression, one of the most recent factors to be identified as playing a critical role in the development of depression is blood-brain barrier (BBB) disruption. The occurrence of BBB integrity disruption contributes to the disturbance of brain homeostasis and leads to complications of neurological diseases, such as stroke, chronic neurodegenerative disorders, neuroinflammatory disorders. Recently, BBB associated tight junction disruption has been shown to implicate in the pathophysiology of depression and contribute to increased susceptibility to depression. However, the underlying mechanisms and importance of BBB damage in depression remains largely unknown. This review highlights how BBB disruption regulates the depression process and the possible molecular mechanisms involved in development of depression-induced BBB dysfunction. Moreover, insight on promising therapeutic targets for treatment of depression with associated BBB dysfunctions are also discussed.

The prevalence of educational burnout, depression, anxiety, and stress among medical students of the Islamic Azad University in Tehran, Iran

BACKGROUND

Psychological disorders have negative consequences on students' learning and academic performance. In addition, academic burnout is one of the common challenges that affects students' motivation and academic eagerness; however, the determinant is not clear. Medical students, meanwhile, demand special attention due to their professional responsibilities. In this regard, this study is conducted to investigate the academic burnout, rate of depression, anxiety and stress as well as related factors among undergraduate medical students at the Tehran Medical Sciences Islamic Azad University.

METHODS

This cross-sectional and descriptive study was performed on medical students of Islamic Azad University of Tehran in 2017. In phase I, conducted on all stager students, Maslach Burnout questionnaire was used. In phase II, the DASS-42 questionnaire was provided for 123 students, 120 of whom met the inclusion criteria. In addition, another questionnaire including gender, age, lifestyle, marital and financial status, nutrition style, vitamin D deficiency, smoking, study hours per week, work efficiency and distance from the place of residence to the teaching hospital was used. Finally, the data extracted by SPSS version 23 was analyzed at the significance level of 0.05.

RESULTS

In phase I of the study, 17 subjects showed academic burnout (16.3%). Out of all, 76.5% of students with academic burnout did not focus on the study and students' academic burnout was associated with a decrease in their focus (P < 0.05). However, the relationship between academic burnout and other factors was not significant. In phase II, the prevalence of depression, anxiety and stress was 37.5, 41.1 and 30.3%, respectively. The prevalence of severe and very severe degrees that required psychiatric follow-up were 10.5, 10.5 and 7% for depression, anxiety and stress, respectively. According to statistical analyzes, there is a significant direct relationship between anxiety and the distance from the place of residence to the teaching hospital (P = 0.040).

CONCLUSION

The present study estimated the prevalence of academic burnout to be between 9.2 and 23.4%, considering the 5% error in the calculation, and the level of anxiety was related to the distance from the place of residence to the hospital.

Evolution of stress responses refine mechanisms of social rank

Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.

Effectiveness of resistance training on resilience in Hong Kong Chinese older adults: study protocol for a randomized controlled trial

Background

There is on one hand sufficient evidence showing strong association between resilience and self-rated successful aging. On the other hand, strength training could contribute the cultivation of resilience among older adults. Therefore, the current study aims to examine the effectiveness of resistance training on resilience among Chinese older adults in Hong Kong.

Methods

This study will apply a three-group, double blinded (outcome assessors and data analysts), randomized controlled trial (RCT) to examine the effectiveness of the interventions on resilience, functional fitness, and health related quality of life immediately after a 16-week intervention, as well as the residual effects 12 weeks after completion of the interventions.

Discussion

It is expected that resistance training is promising or even superior to aerobic training in the improvement of resilience. Given the limited evidence on the literature, it is urgently needed to explore the effects of resistance training on the improvement of resilience in older adults. Findings of the current study can contribute to the development of effective resistant training programs for the promotion of resilience among older adults.

Trial registration

The trial is registered at the ClinicalTrials.gov PRS (Trial ID: NCT04690465; Date of First Posted: 30/12/2020).

Suppression of food restriction-evoked hyperactivity in activity-based anorexia animal model through glutamate transporters GLT-1 at excitatory synapses in the hippocampus

Severe voluntary food restriction is the defining symptom of anorexia nervosa (AN), but anxiety and excessive exercise are maladaptive symptoms that contribute significantly to the severity of AN and which individuals with AN have difficulty suppressing. We hypothesized that the excitability of hippocampal pyramidal neurons, known to contribute to anxiety, leads to the maladaptive behavior of excessive exercise. Conversely, since glutamate transporter GLT-1 dampens the excitability of hippocampal pyramidal neurons through the uptake of ambient glutamate and suppression of the GluN2B-subunit containing NMDA receptors (GluN2B-NMDARs), GLT-1 may contribute toward dampening excessive exercise. This hypothesis was tested using the mouse model of AN, called activity-based anorexia (ABA), whereby food restriction evokes the maladaptive behavior of excessive wheel running (food restriction-evoked running, FRER). We tested whether individual differences in ABA vulnerability of mice, quantified based on FRER, correlated with individual differences in the levels of GLT-1 at excitatory synapses of the hippocampus. Electron microscopic immunocytochemistry (EM-ICC) was used to quantify GLT-1 levels at the excitatory synapses of the hippocampus. The FRER seen in individual mice varied more than 10-fold, and Pearson correlation analyses revealed a strong negative correlation (p = .02) between FRER and GLT-1 levels at the axon terminals of excitatory synapses and at the surrounding astrocytic plasma membranes. Moreover, synaptic levels of GluN2B-NMDARs correlated strongly with GLT-1 levels at perisynaptic astrocytic plasma membranes. There is at present no accepted pharmacotherapy for AN, and little is known about the etiology of this deadly illness. Current findings suggest that drugs increasing GLT-1 expression may reduce AN severity through the reduction of GluN2B-NMDAR activity.

Importance of Non-pharmacological Approaches for Treating Irritable Bowel Syndrome: Mechanisms and Clinical Relevance

Chronic visceral pain represents a major unmet clinical need with the severity of pain ranging from mild to so severe as to prevent individuals from participating in day-to-day activities and detrimentally affecting their quality of life. Although chronic visceral pain can be multifactorial with many different biological and psychological systems contributing to the onset and severity of symptoms, one of the major triggers for visceral pain is the exposure to emotional and physical stress. Chronic visceral pain that is worsened by stress is a hallmark feature of functional gastrointestinal disorders such as irritable bowel syndrome (IBS). Current pharmacological interventions for patients with chronic visceral pain generally lack efficacy and many are fraught with unwanted side effects. Cognitive behavioral therapy (CBT) has emerged as a psychotherapy that shows efficacy at ameliorating stress-induced chronic visceral pain; however, the molecular mechanisms underlying CBT remain incompletely understood. Preclinical studies in experimental models of stress-induced visceral pain employing environmental enrichment (EE) as an animal model surrogate for CBT are unraveling the mechanism by which environmental signals can lead to long-lasting changes in gene expression and behavior. Evidence suggests that EE signaling interacts with stress and nociceptive signaling. This review will (1) critically evaluate the behavioral and molecular changes that lead to chronic pain in IBS, (2) summarize the pharmacological and non-pharmacological approaches used to treat IBS patients, and (3) provide experimental evidence supporting the potential mechanisms by which CBT ameliorates stress-induced visceral pain.

Sex differences in resilience: Experiential factors and their mechanisms

Adverse life events can lead to stable changes in brain structure and function and are considered primary sources of risk for post-traumatic stress disorder, depression and other neuropsychiatric disorders. However, most individuals do not develop these conditions following exposure to traumatic experiences, and research efforts have identified a number of experiential factors associated with an individual's ability to withstand, adapt to and facilitate recovery from adversity. While multiple animal models of stress resilience exist, so that the detailed biological mechanisms can be explored, studies have been disproportionately conducted in male subjects even though the prevalence and presentation of stress-linked disorders differ between sexes. This review focuses on (a) the mechanisms by which experiential factors (behavioral control over a stressor, exercise) reduce the impact of adverse events as studied in males; (b) whether other manipulations (ketamine) that buffer against stress-induced sequelae engage the same circuit features; and (c) whether these processes operate similarly in females. We argue that investigation of experiential factors that produce resistance/resilience rather than vulnerability to adversity will generate a unique set of biological mechanisms that potentially underlie sex differences in mood disorders.

Physical exercise modifies behavioral and molecular parameters related to opioid addiction regardless of training time

Addiction is a devastating worldwide disorder that requires effective and innovative therapies. Physical exercise could be useful in addiction treatment because it shares a common neural circuit with addictive drugs. Based on this, molecular adaptations consequent to time of exercise in opioid exposed animals were evaluated. Rats were designed as sedentary (SED) or exercised (EXE). This last group was separated to perform three different periods of swimming: short-term (S-EXE), medium-term (M-EXE) and long-term (L-EXE) for 14, 28 and 42 days, respectively. On the last exercising week, one-half of the animals from SED and all animals from S-, M- and l-EXE were concomitantly exposed to morphine-conditioned place preference (CPP) paradigm and y-maze task for behavioral assessments followed by molecular assays in both Nucleus accumbens (NAc) and hippocampus. Between SED groups, morphine conditioning showed drug-CPP and increased dopamine transporter (DAT), dopamine receptor type-1 (D1R), type-2 (D2R) and glucocorticoid receptor (GR) in both brain areas in relation to saline group. Besides the small morphine-CPP in relation to SED group, all periods decreased DAT, D1R, and GR immunoreactivity in NAc, DAT and D1R in hippocampus, while D2R in both brain areas and GR in hippocampus were primarily decreased by L-EXE. Our findings show that even a short-term exercise modifies behaviors related to drug withdrawal, changing DA targets and GR, which are closely linked to addiction. Therefore, our outcomes involving physical exercise are interesting to perform a possible clinical trial, thus expanding the knowledge about drug addiction.

Exercise-Induced Adaptations to the Mouse Striatal Adenosine System

Adenosine acts as a key regulator of striatum activity, in part, through the antagonistic modulation of dopamine activity. Exercise can increase adenosine activity in the brain, which may impair dopaminergic functions in the striatum. Therefore, long-term repeated bouts of exercise may subsequently generate plasticity in striatal adenosine systems in a manner that promotes dopaminergic activity. This study investigated the effects of long-term voluntary wheel running on adenosine 1 (A₁R), adenosine 2A (A_2AR), dopamine 1 (D₁R), and dopamine 2 (D₂R) receptor protein expression in adult mouse dorsal and ventral striatum structures using immunohistochemistry. In addition, equilibrative nucleoside transporter 1 (ENT1) protein expression was examined after wheel running, as ENT1 regulates the bidirectional flux of adenosine between intra- and extracellular space. The results suggest that eight weeks of running wheel access spared age-related increases of A₁R and A_2AR protein concentrations across the dorsal and ventral striatal structures. Wheel running mildly reduced ENT1 protein levels in ventral striatum subregions. Moreover, wheel running mildly increased D₂R protein density within striatal subregions in the dorsal medial striatum, nucleus accumbens core, and the nucleus accumbens shell. However, D₁R protein expression in the striatum was unchanged by wheel running. These data suggest that exercise promotes adaptations to striatal adenosine systems. Exercise-reduced A₁R and A_2AR and exercise-increased D₂R protein levels may contribute to improved dopaminergic signaling in the striatum. These findings may have implications for cognitive and behavioral processes, as well as motor and psychiatric diseases that involve the striatum.

Behavioral Traits Associated With Resilience to the Effects of Repeated Social Defeat on Cocaine-Induced Conditioned Place Preference in Mice

The relationship between stress and drug use is well demonstrated. Stress-induced by repeated social defeat (RSD) enhances the conditioned place preference (CPP) induced by cocaine in mice. The phenomenon of resilience understood as the ability of subjects to overcome the negative effects of stress is the focus of increasing interest. Our aim is to characterize the behavior of resilient animals with respect to the effects of RSD on the CPP induced by cocaine. To this end, 25 male C57BL/6 mice were exposed to stress by RSD during late adolescence, while other 15 male mice did not undergo stress (controls). On the 2 days following the last defeat, all the animals carried out the elevated plus maze (EPM) and Hole Board, Social Interaction, Tail Suspension and Splash tests. Three weeks later, all the animals performed the CPP paradigm with a low dose of cocaine (1 mg/kg). Exposure to RSD decreased all measurements related to the open arms of the EPM. It also reduced social interaction, immobility in the tail suspension test (TST) and grooming in the splash test. RSD exposure also increased the sensitivity of the mice to the rewarding effects of cocaine, since only defeated animals acquired CPP. Several behavioral traits were related to resilience to the potentiating effect of RSD on cocaine CPP. Mice that showed less submission during defeat episodes, a lower percentage of time in the open arms of the EPM, low novelty-seeking, high social interaction, greater immobility in the TST and a higher frequency of grooming were those that were resilient to the long-term effects of social defeat on cocaine reward since they behaved like controls and did not develop CPP. These results suggest that the behavioral profile of resilient defeated mice is characterized by an active coping response during episodes of defeat, a greater concern for potential dangers, less reactivity in a situation of inevitable moderate stress and fewer depressive-like symptoms after stress. Determining the neurobehavioral substrates of resilience is the first step towards developing behavioral or pharmacological interventions that increase resilience in individuals at a high risk of suffering from stress.

Effects of repeated voluntary or forced exercise on brainstem serotonergic systems in rats

Voluntary exercise increases stress resistance by modulating stress-responsive neurocircuitry, including brainstem serotonergic systems. However, it remains unknown how exercise produces adaptations to serotonergic systems. Recruitment of serotonergic systems during repeated, daily exercise could contribute to the adaptations in serotonergic systems following exercise, but whether repeated voluntary exercise recruits serotonergic systems is unknown. In this study, we investigated the effects of six weeks of voluntary or forced exercise on rat brain serotonergic systems. Specifically, we analyzed c-Fos and FosB/ΔFosB as markers of acute and chronic cellular activation, respectively, in combination with tryptophan hydroxylase, a marker of serotonergic neurons, within subregions of the dorsal raphe nucleus using immunohistochemical staining. Compared to sedentary controls, rats exposed to repeated forced exercise, but not repeated voluntary exercise, displayed decreased c-Fos expression in serotonergic neurons in the rostral dorsal portion of the dorsal raphe nucleus (DRD) and increased c-Fos expression in serotonergic neurons in the caudal DR (DRC), and interfascicular part of the dorsal raphe nucleus (DRI) during the active phase of the diurnal activity rhythm. Similarly, increases in c-Fos expression in serotonergic neurons in the DRC, DRI, and ventral portion of the dorsal raphe nucleus (DRV) were observed in rats exposed to repeated forced exercise, compared to rats exposed to repeated voluntary exercise. Six weeks of forced exercise, relative to the sedentary control condition, also increased FosB/ΔFosB expression in DRD, DRI, and DRV serotonergic neurons. While both voluntary and forced exercise increase stress resistance, these results suggest that repeated forced exercise, but not repeated voluntary exercise, increases activation of DRI serotonergic neurons, an effect that may contribute to the stress resistance effects of forced exercise. These results also suggest that mechanisms of exercise-induced stress resistance may differ depending on the controllability of the exercise.

Group II metabotropic glutamate receptor blockade promotes stress resilience in mice

Stress is a leading risk factor for the onset and recurrence of major depression. Enhancing stress resilience may be a therapeutic strategy to prevent the development of depression in at-risk populations or its recurrence in depressed patients. Group II metabotropic glutamate receptor (mGlu_2/3) antagonists have been recognized for antidepressant-like actions in preclinical models, but have not been evaluated for prophylactic effects. We assessed the role of mGlu_2/3 in modulating stress resilience using subtype-specific knockout mice lacking mGlu₂ (Grm2^-/-) or mGlu₃ (Grm3^-/-), and pharmacological manipulations of mGlu_2/3 activity during or prior to the induction and reinstatement of stress-induced behavioral deficits. Grm2^-/-, but not Grm3^-/-, mice exhibited reduced forced-swimming test immobility time and were resilient to developing inescapable shock (IES)-induced escape deficits. Grm2^-/- mice were also resilient to developing corticosterone (CORT)-induced escape deficits and chronic social defeat stress-induced anhedonia. Pharmacological blockade of mGlu_2/3 with the antagonist LY341495 during stress prevented the development of IES- and CORT-induced escape deficits, while activation with the agonist LY379268 increased susceptibility to escape deficits. Prophylactic treatment with the LY341495, both systemically and via microinjection into the medial prefrontal cortex (mPFC), up to 7 days before IES, prevented both the induction of escape deficits and their reinstatement by brief re-exposure to IES up to 20 days after treatment. Overall, blockade of mGlu_2/3 enhanced stress resilience and deletion of mGlu₂, but not mGlu₃, conferred a stress-resilient phenotype, indicating that prophylactic treatments reducing mGlu₂ activity may protect against stress-induced changes underlying the development or recurrence of stress-induced disorders, including depression.

Dissociation in Effective Treatment and Behavioral Phenotype Between Stress-Enhanced Fear Learning and Learned Helplessness

Post-traumatic stress disorder (PTSD) is a debilitating disease with relatively high lifetime prevalence. It is marked by a high diversity of symptoms and comorbidity with other psychiatric disease. Furthermore, PTSD has a high level of origin and symptom heterogeneity within the population. These characteristics taken together make it one of the most challenging diseases to effectively model in animals. However, with relatively little headway made in developing effective disease interventions, PTSD remains as a high priority target for animal model study. Learned Helplessness (LH) is a procedure classically used to model depression, but has in recent years transitioned to use as a model of PTSD. Animals in this procedure receive 100 inescapable and unpredictable tailshocks or simple restraint without shock. The following day, the animals are tested in a shuttle box, where inescapably-shocked subjects exhibit exaggerated fear and profound deficit in escape performance. Stress-enhanced fear learning (SEFL) also uses an acute (single session) stressor for modeling PTSD in rodents. The SEFL procedure begins with exposure to 15 footshocks or simple context exposure without shock. Animals that initially received the 15 footshocks exhibit future enhanced fear learning. In this review, we will compare the behavior, physiology, and interventions of these two animal models of PTSD. Despite considerable similarity (a single session containing inescapable and uncontrollable shock) the two procedures produce a very divergent set of behavioral consequences.

Increased locomotor activity in estrogen-treated ovariectomized rats is associated with nucleus accumbens dopamine and is not reduced by dietary sodium deprivation

Estrogens are well known to increase locomotor activity in laboratory rodents; however, the underlying mechanism remains unclear. We used voluntary wheel running by female rats as an index of locomotor behavior to investigate this issue. We first determined whether the estrogen-induced increase in locomotion was susceptible to inhibition by a physiological challenge, and next whether it was associated with dopaminergic activation in the central reward area, nucleus accumbens. Ovariectomized rats were given estradiol or the oil vehicle and housed in cages with or without running wheels. All rats were given regular rodent chow for 1 week, a sodium-deficient diet for the next week, and then were returned to a regular diet for another week. At the end of the last week, all rats were killed, brains were extracted and dopamine levels in the nucleus accumbens were measured. As expected, estradiol treatment increased distance run. Surprisingly, dietary sodium deprivation further increased running, but this appeared to be related to experience with wheel running, rather than to sodium deprivation, per se. Dopamine was greater in the nucleus accumbens of estradiol-treated rats that ran compared to all other groups. Thus, the estrogen-induced increase in locomotion is a robust phenomenon that is not inhibited by a body sodium challenge and is associated with elevated levels of dopamine in reward pathways. These findings raise the possibility that the estrogen-induced increase in locomotor activity, which occurs during a hormonal milieu conducive to reproduction, may reflect mate-seeking behavior and, thereby, maximize reproductive success.

Voluntary wheel running promotes resilience to chronic social defeat stress in mice: a role for nucleus accumbens ΔFosB

Elucidating mechanisms by which physical exercise promotes resilience, the brain's ability to cope with prolonged stress exposure while maintaining normal psychological functioning, is a major research challenge given the high prevalence of stress-related mental disorders, including major depressive disorder. Chronic voluntary wheel running (VWR), a rodent model that mimics aspects of human physical exercise, induces the transcription factor ΔFosB in the nucleus accumbens (NAc), a key reward-related brain area. ΔFosB expression in NAc modulates stress susceptibility. Here, we explored whether VWR induction of NAc ΔFosB promotes resilience to chronic social defeat stress (CSDS). Male young-adult C57BL/6J mice were single housed for up to 21 d with or without running wheels and then subjected to 10 d of CSDS. Stress-exposed sedentary mice developed a depressive-like state, characterized by anhedonia and social avoidance, whereas stress-exposed mice that had been wheel running showed resilience. Functional inhibition of NAc ΔFosB during VWR, by viral-mediated overexpression of a transcriptionally inactive JunD mutant, reinstated susceptibility to CSDS. Within the NAc, VWR induction of ΔFosB was CREB-dependent, associated with altered dendritic morphology, and medium spiny neuron (MSN) subtype specific in the NAc core and shell subregions. Finally, when mice performed VWR following the onset of CSDS-induced social avoidance, VWR normalized such behavior. These data indicate that VWR promoted resilience to CSDS, and suggest that sustained induction of ΔFosB in the NAc underlies, at least in part, the stress resilience mediated by VWR. These findings provide a potential framework for the development of treatments for stress-associated mental illnesses based on physical exercise.

Immune and Neuroprotective Effects of Physical Activity on the Brain in Depression

Physical activity-a lifestyle factor that is associated with immune function, neuroprotection, and energy metabolism-modulates the cellular and molecular processes in the brain that are vital for emotional and cognitive health, collective mechanisms that can go awry in depression. Physical activity optimizes the stress response, neurotransmitter level and function (e.g., serotonergic, noradrenergic, dopaminergic, and glutamatergic), myokine production (e.g., interleukin-6), transcription factor levels and correlates [e.g., peroxisome proliferator-activated receptor C coactivator-1α [PGC-1α], mitochondrial density, nitric oxide pathway activity, Ca2+ signaling, reactive oxygen specie production, and AMP-activated protein kinase [AMPK] activity], kynurenine metabolites, glucose regulation, astrocytic health, and growth factors (e.g., brain-derived neurotrophic factor). Dysregulation of these interrelated processes can effectuate depression, a chronic mental illness that affects millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility in understanding chronic depression, a need remains to better understand the interrelated mechanisms that contribute to immune dysfunction and the means by which various therapeutics mitigate them. Fortunately, convergent evidence suggests that physical activity improves emotional and cognitive function in persons with depression, particularly in those with comorbid inflammation. Accordingly, the aims of this review are to (1) underscore the link between inflammatory correlates and depression, (2) explicate immuno-neuroendocrine foundations, (3) elucidate evidence of neurotransmitter and cytokine crosstalk in depressive pathobiology, (4) determine the immunomodulatory effects of physical activity in depression, (5) examine protocols used to effectuate the positive effects of physical activity in depression, and (6) highlight implications for clinicians and scientists. It is our contention that a deeper understanding of the mechanisms by which inflammation contributes to the pathobiology of depression will translate to novel and more effective treatments, particularly by identifying relevant patient populations that can benefit from immune-based therapies within the context of personalized medicine.

Effects of a 12-week running programme in youth and adults with complex mood disorders

Objective

Although numerous studies suggest a salutary effect of exercise on mood, few studies have explored the effect of exercise in patients with complex mental illness. Accordingly, we evaluated the impact of running on stress, anxiety and depression in youth and adults with complex mood disorders including comorbid diagnoses, cognitive and social impairment and high relapse rates.

Methods

Participants were members of a running group at St Joseph Healthcare Hamilton’s Mood Disorders Program, designed for clients with complex mood disorders. On a weekly basis, participants completed Cohen’s Perceived Stress Scale, Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI) questionnaires, providing an opportunity to evaluate the effect of running in this population.

Results

Data collected for 46 participants from April 2012 to July 2015 indicated a significant decrease in depression (p<0.0001), anxiety (p<0.0001) and stress (p=0.01) scores. Whereas younger participant age, younger age at onset of illness and higher perceived levels of friendship with other running group members (ps≤0.04) were associated with lower end-of-study depression, anxiety and stress scores, higher attendance was associated with decreasing BDI and BAI (ps≤0.01) scores over time.

Conclusions

Aerobic exercise in a supportive group setting may improve mood symptoms in youth and adults with complex mood disorders, and perceived social support may be an important factor in programme’s success. Further research is required to identify specifically the mechanisms underlying the therapeutic benefits associated with exercise-based therapy programmes.

The influence of exercise on anxiety-like behavior in zebrafish (Danio rerio)

In non-human mammals, exercise has been shown to decrease anxiety-like behavior. Conversely, a number of studies have reported no effect or even an increase in anxiety-like behavior after exercise, however, inconsistent training regimes and behavioral paradigms across studies may be confounding the results. Zebrafish (Danio rerio) are a well-established animal model in neurobehavioral research, and have the potential to shed new insight into the effects of exercise on anxiety-like behavior where previous research has been limited, due to the ability to precisely control intensity and duration of exercise, and the validation of tests for measuring different aspects of anxiety-like behaviors. In the current study, fish were split between two treatment groups; Exercised and Control. Fish in the exercised condition were aerobically challenged (max water velocity: 0.5 m/s) using a swim tunnel one hour a day, five days a week, for six weeks. Control fish spent an equal amount of time in the swim tunnel but were not aerobically challenged (max water velocity: 0.05 m/s). After six weeks, all fish were tested individually in two standard complimentary anxiety tests for zebrafish: the novel tank test and the light-dark test. Exercised fish exhibited reduced anxiety-like behaviors in the novel tank test; they spent more time in the top and were quicker to enter the top of a novel tank compared to Control fish. In addition, Exercised fish spent more time in the light compartment of the light-dark test compared to Control fish. Our results demonstrate the beneficial effect of exercise on anxiety-like behavior in zebrafish.

Voluntary exercise and depression-like behavior in rodents: are we running in the right direction?

Acute or chronic exposure to stress can increase the risk to develop major depressive disorder, a severe, recurrent and common psychiatric condition. Depression places an enormous social and financial burden on modern society. Although many depressed patients are treated with antidepressants, their efficacy is only modest, underscoring the necessity to develop clinically effective pharmaceutical or behavioral treatments. Exercise training produces beneficial effects on stress-related mental disorders, indicative of clinical potential. The pro-resilient and antidepressant effects of exercise training have been documented for several decades. Nonetheless, the underlying molecular mechanisms and the brain circuitries involved remain poorly understood. Preclinical investigations using voluntary wheel running, a frequently used rodent model that mimics aspects of human exercise training, have started to shed light on the molecular adaptations, signaling pathways and brain nuclei underlying the beneficial effects of exercise training on stress-related behavior. In this review, I highlight several neurotransmitter systems that are putative mediators of the beneficial effects of exercise training on mental health, and review recent rodent studies that utilized voluntary wheel running to promote our understanding of exercise training-induced central adaptations. Advancements in our mechanistic understanding of how exercise training induces beneficial neuronal adaptations will provide a framework for the development of new strategies to treat stress-associated mental illnesses.

Physical Activity Modulates Common Neuroplasticity Substrates in Major Depressive and Bipolar Disorder

Mood disorders (MDs) are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility, a need remains to better understand the interrelated mechanisms that contribute to neuroplasticity deficits in MDs and the means by which various therapeutics mitigate them. Of those therapeutics being investigated, physical activity (PA) has shown clear and consistent promise. Accordingly, the aims of this review are to (1) explicate key modulators, processes, and interactions that impinge upon multiple susceptibility points to effectuate neuroplasticity deficits in MDs; (2) explore the putative mechanisms by which PA mitigates these features; (3) review protocols used to induce the positive effects of PA in MDs; and (4) highlight implications for clinicians and researchers.

Brain metabolism in health, aging, and neurodegeneration

Brain cells normally respond adaptively to bioenergetic challenges resulting from ongoing activity in neuronal circuits, and from environmental energetic stressors such as food deprivation and physical exertion. At the cellular level, such adaptive responses include the "strengthening" of existing synapses, the formation of new synapses, and the production of new neurons from stem cells. At the molecular level, bioenergetic challenges result in the activation of transcription factors that induce the expression of proteins that bolster the resistance of neurons to the kinds of metabolic, oxidative, excitotoxic, and proteotoxic stresses involved in the pathogenesis of brain disorders including stroke, and Alzheimer's and Parkinson's diseases. Emerging findings suggest that lifestyles that include intermittent bioenergetic challenges, most notably exercise and dietary energy restriction, can increase the likelihood that the brain will function optimally and in the absence of disease throughout life. Here, we provide an overview of cellular and molecular mechanisms that regulate brain energy metabolism, how such mechanisms are altered during aging and in neurodegenerative disorders, and the potential applications to brain health and disease of interventions that engage pathways involved in neuronal adaptations to metabolic stress.

Inadequate Sleep and Exercise Associated with Burnout and Depression Among Medical Students

OBJECTIVE

The authors studied whether low levels of exercise or inadequate sleep correlated with higher levels of burnout and depression in medical students.

METHODS

Medical students of all years at the University of Pittsburgh School of Medicine, Pittsburgh, PA, USA, were invited to participate in an anonymous online survey in Fall 2012 and Winter 2013. Validated measures were used to assess exercise, sleep, burnout, and depression.

RESULTS

Response rates were 28.7 % at the beginning of the school year and 22.6 % at the middle of the school year. Burnout rates overall were 22.4 % at the beginning of the year and 19.2 % in the middle of the year. Eight percent of students screened positive for depression at the beginning of the year and 9.3 % in the middle of the year. Decreased exercise frequency was significantly correlated with lower professional efficacy. Pathological sleepiness was significantly associated with a higher prevalence of burnout. Inadequate sleep correlated with significantly lower professional efficacy and higher exhaustion scores. Burnout was associated with a positive depression screen. Positive depression screening, pathological sleepiness, and sleeping less than 7 h a night were independent predictors of burnout.

CONCLUSIONS

Sleep habits, exercise, and a positive depression screen were associated with burnout risk within the medical student population.

The Effects of Acute Exercise on Mood, Cognition, Neurophysiology, and Neurochemical Pathways: A Review

A significant body of work has investigated the effects of acute exercise, defined as a single bout of physical activity, on mood and cognitive functions in humans. Several excellent recent reviews have summarized these findings; however, the neurobiological basis of these results has received less attention. In this review, we will first briefly summarize the cognitive and behavioral changes that occur with acute exercise in humans. We will then review the results from both human and animal model studies documenting the wide range of neurophysiological and neurochemical alterations that occur after a single bout of exercise. Finally, we will discuss the strengths, weaknesses, and missing elements in the current literature, as well as offer an acute exercise standardization protocol and provide possible goals for future research.

Negative rebound in hippocampal neurogenesis following exercise cessation

Physical exercise can improve brain function, but the effects of exercise cessation are largely unknown. This study examined the time-course profile of hippocampal neurogenesis following exercise cessation. Male C57BL/6 mice were randomly assigned to either a control (Con) or an exercise cessation (ExC) group. Mice in the ExC group were reared in a cage with a running wheel for 8 wk and subsequently placed in a standard cage to cease the exercise. Exercise resulted in a significant increase in the density of doublecortin (DCX)-positive immature neurons in the dentate gyrus (at week 0). Following exercise cessation, the density of DCX-positive neurons gradually decreased and was significantly lower than that in the Con group at 5 and 8 wk after cessation, indicating that exercise cessation leads to a negative rebound in hippocampal neurogenesis. Immunohistochemistry analysis suggests that the negative rebound in neurogenesis is caused by diminished cell survival, not by suppression of cell proliferation and neural maturation. Neither elevated expression of ΔFosB, a transcription factor involved in neurogenesis regulation, nor increased plasma corticosterone, were involved in the negative neurogenesis rebound. Importantly, exercise cessation suppressed ambulatory activity, and a significant correlation between change in activity and DCX-positive neuron density suggested that the decrease in activity is involved in neurogenesis impairment. Forced treadmill running following exercise cessation failed to prevent the negative neurogenesis rebound. This study indicates that cessation of exercise or a decrease in physical activity is associated with an increased risk for impaired hippocampal function, which might increase vulnerability to stress-induced mood disorders.

The exercise-glucocorticoid paradox: How exercise is beneficial to cognition, mood, and the brain while increasing glucocorticoid levels

Exercise is known to have beneficial effects on cognition, mood, and the brain. However, exercise also activates the hypothalamic-pituitary-adrenal axis and increases levels of the glucocorticoid cortisol (CORT). CORT, also known as the "stress hormone," is considered a mediator between chronic stress and depression and to link various cognitive deficits. Here, we review the evidence that shows that while both chronic stress and exercise elevate basal CORT levels leading to increased secretion of CORT, the former is detrimental to cognition/memory, mood/stress coping, and brain plasticity, while the latter is beneficial. We propose three preliminary answers to the exercise-CORT paradox. Importantly, the elevated CORT, through glucocorticoid receptors, functions to elevate dopamine in the medial prefrontal cortex under chronic exercise but not chronic stress, and the medial prefrontal dopamine is essential for active coping. Future inquiries may provide further insights to promote our understanding of this paradox.

Manganese and the Insulin-IGF Signaling Network in Huntington's Disease and Other Neurodegenerative Disorders

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease resulting in motor impairment and death in patients. Recently, several studies have demonstrated insulin or insulin-like growth factor (IGF) treatment in models of HD, resulting in potent amelioration of HD phenotypes via modulation of the PI3K/AKT/mTOR pathways. Administration of IGF and insulin can rescue microtubule transport, metabolic function, and autophagy defects, resulting in clearance of Huntingtin (HTT) aggregates, restoration of mitochondrial function, amelioration of motor abnormalities, and enhanced survival. Manganese (Mn) is an essential metal to all biological systems but, in excess, can be toxic. Interestingly, several studies have revealed the insulin-mimetic effects of Mn-demonstrating Mn can activate several of the same metabolic kinases and increase peripheral and neuronal insulin and IGF-1 levels in rodent models. Separate studies have shown mouse and human striatal neuroprogenitor cell (NPC) models exhibit a deficit in cellular Mn uptake, indicative of a Mn deficiency. Furthermore, evidence from the literature reveals a striking overlap between cellular consequences of Mn deficiency (i.e., impaired function of Mn-dependent enzymes) and known HD endophenotypes including excitotoxicity, increased reactive oxygen species (ROS) accumulation, and decreased mitochondrial function. Here we review published evidence supporting a hypothesis that (1) the potent effect of IGF or insulin treatment on HD models, (2) the insulin-mimetic effects of Mn, and (3) the newly discovered Mn-dependent perturbations in HD may all be functionally related. Together, this review will present the intriguing possibility that intricate regulatory cross-talk exists between Mn biology and/or toxicology and the insulin/IGF signaling pathways which may be deeply connected to HD pathology and, perhaps, other neurodegenerative diseases (NDDs) and other neuropathological conditions.

Running Opposes the Effects of Social Isolation on Synaptic Plasticity and Transmission in a Rat Model of Depression

Stress, such as social isolation, is a well-known risk factor for depression, most probably in combination with predisposing genetic factors. Physical exercise on the other hand, is depicted as a wonder-treatment that makes you healthier, happier and live longer. However, the published results on the effects of exercise are ambiguous, especially when it comes to neuropsychiatric disorders. Here we combine a paradigm of social isolation with a genetic rat model of depression, the Flinders Sensitive Line (FSL), already known to have glutamatergic synaptic alterations. Compared to group-housed FSL rats, we found that social isolation further affects synaptic plasticity and increases basal synaptic transmission in hippocampal CA1 pyramidal neurons. These functional synaptic alterations co-exist with changes in hippocampal protein expression levels: social isolation in FSL rats reduce expression of the glial glutamate transporter GLT-1, and increase expression of the GluA2 AMPA-receptor subunit. We further show that physical exercise in form of voluntary running prevents the stress-induced synaptic effects but do not restore the endogenous mechanisms of depression already present in the FSL rat.

Exercise and Prebiotics Produce Stress Resistance: Converging Impacts on Stress-Protective and Butyrate-Producing Gut Bacteria

The gut microbial ecosystem can mediate the negative health impacts of stress on the host. Stressor-induced disruptions in microbial ecology (dysbiosis) can lead to maladaptive health effects, while certain probiotic organisms and their metabolites can protect against these negative impacts. Prebiotic diets and exercise are feasible and cost-effective strategies that can increase stress-protective bacteria and produce resistance against the detrimental behavioral and neurobiological impacts of stress. The goal of this review is to describe research demonstrating that both prebiotic diets and exercise produce adaptations in gut ecology and the brain that arm the organism against inescapable stress-induced learned helplessness. The results of this research support the novel hypothesis that some of the stress-protective effects of prebiotics and exercise are due to increases in stress-protective gut microbial species and their metabolites. In addition, new evidence also suggests that prebiotic diet or exercise interventions are most effective if given early in life (juvenile-adolescence) when both the gut microbial ecosystem and the brain are plastic. Based on our new understanding of the mechanistic convergence of these interventions, it is feasible to propose that in adults, both interventions delivered in combination may elevate their efficacy to promote a stress-resistant phenotype.

Greater levels of cardiorespiratory and muscular fitness are associated with low stress and high mental resources in normal but not overweight men

Background

The aim of the present study was to investigate how cardio respiratory (CRF) and muscular fitness (MF) together with leisure-time physical activity (LTPA) influence stress symptoms and mental resources among normal-weight and overweight men, because it is not known how body weight affects this association.

Methods

In a cross-sectional study, 824 men (mean ± SD: age 25 ± 5 y, weight 81 ± 13 kg, BMI 25 ± 4 kg/m²) underwent CRF and MF tests and completed LTPA and stress questionnaires. For the analysis, the subjects were divided into BMI groups (normal vs. overweight) and CRF / MF / LTPA (low, moderate, high) tertiles.

Results

Normal-weight men with low CRF reported 12 % (p = 0.001) more stress symptoms (SS) compared to normal-weight men with moderate CRF, and 13 % (p = 0.004) more SS compared to normal-weight men with high CRF. Normal-weight men with low MF reported 13 % (p = 0.001) higher SS compared to normal-weight men with moderate MF and 16 % (p = 0.002) more SS compared to men with high MF. Among overweight men, there were no significant differences in SS or mental resources (MR) between the low, moderate and high CRF and MF tertiles. Overweight men with high CRF experienced 8 % (p = 0.039) more SS compared to normal-weight participants with high CRF when age, tobacco and alcohol use, MF and LTPA were considered as covariates (p = 0.014).

Conclusion

Higher CRF and MF are associated with lower stress and higher mental resources in normal-weight men, but in overweight men, these relationships may differ.

The role of medial prefrontal corticosterone and dopamine in the antidepressant-like effect of exercise

Despite the well-documented beneficial effect of exercise on stress coping and depression treatment, its underlying neurobiological mechanism remains unclear. This is further complicated by a 'side effect' of exercise: it increases basal glucocorticoid (CORT), the stress hormone, which has been shown to be a mediator linking stress to depressive disorders. Here we show that three weeks of voluntary wheel running reduced rats' immobility in the forced swim test (FST), an antidepressant-like effect. Monitoring extracellular fluids in the medial prefrontal cortex PFC (mPFC) using microdialysis we found that, wheel running was associated with higher baseline CORT, but lower FST-responsive CORT. Further, wheel running resulted in a higher dopamine (DA) both at baseline and following FST. Interestingly, the antidepressant-like effect of wheel running was completely abolished by intra-mPFC pre-microinjection of a D2R (haloperidol) but not D1R (SCH23390) antagonist, at a dose that does not affect normal rats' performance in the FST. It suggests that exercise exerts antidepressant-like effect through upregulated DA and in a D2R dependent way in the mPFC. Importantly, the antidepressant-like effect of wheel running was also abolished by intra-mPFC pre-microinjection of a GR antagonist (RU486). Finally, intra-mPFC pre-microinjection of RU486 also downregulated the originally elevated basal and FST-responsive DA in the mPFC of exercise rats. These results suggest a causal pathway linking CORT, GR, DA, and D2R, to the antidepressant-like effect of exercise. In conclusion, exercise achieves antidepressant-like effect through the CORT-GR-DA-D2R pathway and that the increased basal CORT by exercise itself may be beneficial rather than detrimental.

Estrogen and voluntary exercise interact to attenuate stress-induced corticosterone release but not anxiety-like behaviors in female rats

The beneficial effects of physical exercise to reduce anxiety and depression and to alleviate stress are increasingly supported in research studies. The role of ovarian hormones in interactions between exercise and anxiety/stress has important implications for women's health, given that women are at increased risk of developing anxiety-related disorders, particularly during and after the menopausal transition. In these experiments, we tested the hypothesis that estrogen enhances the positive impact of exercise on stress responses by investigating the combined effects of exercise and estrogen on anxiety-like behaviors and stress hormone levels in female rats after an acute stressor. Ovariectomized female rats with or without estrogen were given access to running wheels for one or three days of voluntary running immediately after or two days prior to being subjected to restraint stress. We found that voluntary running was not effective at reducing anxiety-like behaviors, whether or not rats were subjected to restraint stress. In contrast, stress-induced elevations of stress hormone levels were attenuated by exercise experience in estrogen-treated rats, but were increased in rats without estrogen. These results suggest that voluntary exercise may be more effective at reducing stress hormone levels if estrogen is present. Additionally, exercise experience, or the distance run, may be important in reducing stress.

A Concerted Action Of Estradiol And Insulin Like Growth Factor I Underlies Sex Differences In Mood Regulation By Exercise

Mood homeostasis present sexually dimorphic traits which may explain sex differences in the incidence of mood disorders. We explored whether diverse behavioral-setting components of mood may be differentially regulated in males and females by exercise, a known modulator of mood. We found that exercise decreases anxiety only in males. Conversely, exercise enhanced resilience to stress and physical arousal, two other important components of mood, only in females. Because exercise increases brain input of circulating insulin-like growth factor I (IGF-I), a potent modulator of mood, we explored whether sex-specific actions of exercise on mood homeostasis relate to changes in brain IGF-I input. We found that exercise increased hippocampal IGF-I levels only in cycling females. Underlying mechanism involved activation of estrogen (E₂) receptors in brain vessels that led to increased uptake of serum IGF-I as E₂ was found to stimulate IGF-I uptake in brain endothelial cells. Indeed, modulatory effects of exercise on mood were absent in female mice with low serum IGF-I levels or after either ovariectomy or administration of an E₂ receptor antagonist. These results suggest that sex-specific brain IGF-I responses to physiological stimuli such as exercise contribute to dimorphic mood homeostasis that may explain sex differences in affective disorders.

Cerebellar sub-divisions differ in exercise-induced plasticity of noradrenergic axons and in their association with resilience to activity-based anorexia

The vermis or "spinocerebellum" receives input from the spinal cord and motor cortex for controlling balance and locomotion, while the longitudinal hemisphere region or "cerebro-cerebellum" is interconnected with non-motor cortical regions, including the prefrontal cortex that underlies decision-making. Noradrenaline release in the cerebellum is known to be important for motor plasticity but less is known about plasticity of the cerebellar noradrenergic (NA) system, itself. We characterized plasticity of dopamine β-hydroxylase-immunoreactive NA fibers in the cerebellum of adolescent female rats that are evoked by voluntary wheel running, food restriction (FR) or by both, in combination. When 8 days of wheel access was combined with FR during the last 4 days, some responded with excessive exercise, choosing to run even during the hours of food access: this exacerbated weight loss beyond that due to FR alone. In the vermis, exercise, with or without FR, shortened the inter-varicosity intervals and increased varicosity density along NA fibers, while excessive exercise, due to FR, also shortened NA fibers. In contrast, the hemisphere required the FR-evoked excessive exercise to evoke shortened inter-varicosity intervals along NA fibers and this change was exhibited more strongly by rats that suppressed the FR-evoked excessive exercise, a behavior that minimized weight loss. Presuming that shortened inter-varicosity intervals translate to enhanced NA release and synthesis of norepinephrine, this enhancement in the cerebellar hemisphere may contribute towards protection of individuals from the life-threatening activity-based anorexia via relays with higher-order cortical areas that mediate the animal's decision to suppress the innate FR-evoked hyperactivity.

Seeding Stress Resilience through Inoculation

Stress is a generalized set of physiological and psychological responses observed when an organism is placed under challenging circumstances. The stress response allows organisms to reattain the equilibrium in face of perturbations. Unfortunately, chronic and/or traumatic exposure to stress frequently overwhelms coping ability of an individual. This is manifested as symptoms affecting emotions and cognition in stress-related mental disorders. Thus environmental interventions that promote resilience in face of stress have much clinical relevance. Focus of the bulk of relevant neurobiological research at present remains on negative aspects of health and psychological outcomes of stress exposure. Yet exposure to the stress itself can promote resilience to subsequent stressful episodes later in the life. This is especially true if the prior stress occurs early in life, is mild in its magnitude, and is controllable by the individual. This articulation has been referred to as "stress inoculation," reminiscent of resilience to the pathology generated through vaccination by attenuated pathogen itself. Using experimental evidence from animal models, this review explores relationship between nature of the "inoculum" stress and subsequent psychological resilience.

Running Reduces Uncontrollable Stress-Evoked Serotonin and Potentiates Stress-Evoked Dopamine Concentrations in the Rat Dorsal Striatum

Accumulating evidence from both the human and animal literature indicates that exercise reduces the negative consequences of stress. The neurobiological etiology for this stress protection, however, is not completely understood. Our lab reported that voluntary wheel running protects rats from expressing depression-like instrumental learning deficits on the shuttle box escape task after exposure to unpredictable and inescapable tail shocks (uncontrollable stress). Impaired escape behavior is a result of stress-sensitized serotonin (5-HT) neuron activity in the dorsal raphe (DRN) and subsequent excessive release of 5-HT into the dorsal striatum following exposure to a comparatively mild stressor. However, the possible mechanisms by which exercise prevents stress-induced escape deficits are not well characterized. The purpose of this experiment was to test the hypothesis that exercise blunts the stress-evoked release of 5-HT in the dorsal striatum. Changes to dopamine (DA) levels were also examined, since striatal DA signaling is critical for instrumental learning and can be influenced by changes to 5-HT activity. Adult male F344 rats, housed with or without running wheels for 6 weeks, were either exposed to tail shock or remained undisturbed in laboratory cages. Twenty-four hours later, microdialysis was performed in the medial (DMS) and lateral (DLS) dorsal striatum to collect extracellular 5-HT and DA before, during, and following 2 mild foot shocks. We report wheel running prevents foot shock-induced elevation of extracellular 5-HT and potentiates DA concentrations in both the DMS and DLS approximately 24 h following exposure to uncontrollable stress. These data may provide a possible mechanism by which exercise prevents depression-like instrumental learning deficits following exposure to acute stress.

Oral self-administration of EtOH: sex-dependent modulation by running wheel access in C57BL/6J mice

BACKGROUND

The effects of stress, including neuroendocrine and behavioral sequelae aimed at maintaining homeostasis, are associated with increased alcohol consumption. Because both stress and drinking are multifactorial, the mechanisms underlying the relationship are difficult to elucidate. We therefore employed an animal model investigating the influence of blocked access to a running wheel on drinking in C57BL/6J (B6) mice.

METHODS

In the first experiment, naïve, adult male and female subjects were individually housed for 2 weeks with 24-hour access to a running wheel and 12% ethanol (EtOH) in a 2-bottle, free choice paradigm. After determining baseline consumption and preference, experimental subjects had the running wheel placed in a locked position for 6 hours, and the EtOH bottle was removed during the first half of this period. Two subsequent experiments, again in adult, naïve B6 mice, examined the influence of locked running wheels on self-administration of 20% EtOH in a limited access paradigm, and blood EtOH concentrations (BECs) were determined on the final day of this protocol.

RESULTS

In all 3 studies, using both between- and within-subject analyses, females showed transient yet reliable increases in alcohol drinking during blocked access to a rotating activity, while drinking in male mice was largely insensitive to this manipulation, although both sexes showed appreciable BECs (>130 mg/dl in females and 80 mg/dl in males) following a 2-hour EtOH access period.

CONCLUSIONS

These data add to a burgeoning literature suggesting that the factors contributing to excessive alcohol use differ between males and females and that females may be especially sensitive to the influence of wheel manipulation. Elucidating the sex-dependent mechanisms mediating differences in alcohol sensitivity and response is critical to understanding the causes of alcoholism and in developing effective treatments and interventions.