Does the difference between physically active and couch potato lie in the dopamine system?

The "Vicious Circle of addictive Social Media Use and Mental Health" Model

Social media use (SMU) is a significant part of many people's everyday life. Research around the globe describes an increase of addictive SMU tendencies since the COVID-19 outbreak. The present work combines available findings in the "Vicious Circle of addictive Social Media Use and Mental Health" model to explain how social media (SM) activity can contribute to the development of addictive tendencies, which consequences they have for mental health, and how to prevent them. Following the model, the interplay between the risk factors negative experiences caused by daily hassles and by unexpected global and traumatic events, SMU (dimension "quality"), and SM flow can directly contribute to addictive SMU through the "vicious circle". Time spent on SMU (dimension "quantity"), symptoms of depression and anxiety, and the personality trait narcissism contribute to the circle as moderators. Symptoms of stress, insomnia, and suicide-related outcomes are described as potential consequences of addictive SMU. Based on longitudinal intervention studies, a conscious reduction of SMU time and an increase of physical activity, as well as positive mental health and mindfulness are identified as protective factors that reduce the risk of addictive tendencies. The model contributes to a better understanding of addictive SMU. Implications of the model for future research and praxis, specifically for mental health programs and therapeutic treatment are discussed.

Investigating psychological mechanisms of self-controlled decisions for food and leisure activity

Maintaining a healthy body weight requires balancing energy intake and expenditure. While previous research investigated energy input or food decisions, little is known about energy output or leisure activity decisions. By combining experimental decision-making paradigms and computational approaches, we investigated the psychological mechanisms of self-controlled food and leisure activity decisions through the effects of reward-oriented and health-oriented preferences as well as body weight status, stress, and coping. Based on individual's responses, the self-controlled food and leisure activity choices were indexed as the proportions of "no" unhealthy but tasty (or enjoyable) (inhibitory self-control against short-term pleasure) and "yes" healthy but not tasty (or not enjoyable) responses (initiatory self-control for long-term health benefits). The successful self-control decisions for food and leisure activity were positively correlated with each other, r = 22, p < .01. In beta regression analyses, the successful self-controlled food decisions decreased as the taste-oriented process increased, β = - 0.50, z = -2.99, p < .005, and increased as the health-oriented process increased, β = 1.57, z = 4.68, p < .001. Similarly, the successful self-controlled leisure activity decisions decreased as the enjoyment-oriented process increased, β = - 0.79, z = -5.31, p < .001, and increased as the health-oriented process increased, β = 0.66, z = 2.19, p < .05. The effects of the other factors were not significant. Overall, our findings demonstrated the mutual interrelationship between food and leisure activity decision-making and suggest that encouraging health-oriented processes may benefit both energy input and expenditure domains and improve self-controlled choices.

Sports and Immunity, from the recreational to the elite athlete

The pivotal role of the immune system in physical activity is well-established. While interactions are complex, they tend to constitute discrete immune responses. Moderate intensity exercise causes leukocytosis with a mild anti-inflammatory cytokine profile and immunoenhancement. Above a threshold of intensity, lactate-mediated IL-6 release causes a proinflammatory state followed by a depressed inflammatory state, which stimulates immune adaptation and longer term cardiometabolic enhancement. Exercise-related immune responses are modulated by sex, age and immunonutrition. At all ability levels, these factors collectively affect the immune balance between enhancement or overload and dysfunction. Excessive training, mental stress or insufficient recovery risks immune cell exhaustion and hypothalamic pituitary axis (HPA) stress responses causing immunodepression with negative impacts on performance or general health. Participation in sport provides additional immune benefits in terms of ensuring regularity, social inclusion, mental well-being and healthier life choices in terms of diet and reduced smoking and alcohol, thereby consolidating healthy lifestyles and longer term health. Significant differences exist between recreational and professional athletes in terms of inherent characteristics, training resilience and additional stresses arising from competition schedules, travel-related infections and stress. Exercise immunology examines the central role of immunity in exercise physiology and straddles multiple disciplines ranging from neuroendocrinology to nutrition and genetics, with the aim of guiding athletes to train optimally and safely. This review provides a brief outline of the main interactions of immunity and exercise, some influencing factors, and current guidance on maintaining immune health.

Aerobic Exercise and Endocannabinoids: A Narrative Review of Stress Regulation and Brain Reward Systems

Aerobic exercise is a widely adopted practice, not solely for enhancing fitness and reducing the risk of various diseases but also for its ability to uplift mood and aid in addressing depression and anxiety disorders. Within the scope of this narrative review, we seek to consolidate current insights into the endocannabinoid-mediated regulation of stress and the brain's reward mechanism resulting from engaging in aerobic exercise. A comprehensive search was conducted across Medline, SPORTDiscus, Pubmed, and Scopus, encompassing data available until November 30, 2023. This review indicates that a bout of aerobic exercise, particularly of moderate intensity, markedly augments circulating levels of endocannabinoids - N-arachidonoyl-ethanolamine (AEA) and 2-acylglycerol (2-AG), that significantly contributes to mood elevation and reducing stress in healthy individuals.  The current understanding of how aerobic exercise impacts mental health and mood improvement is still unclear. Moderate and high-intensity aerobic exercise modulates stress through a negative feedback mechanism targeting both the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system, thereby facilitating stress regulation crucial role in endocannabinoid synthesis, ultimately culminating in the orchestration of negative feedback across multiple tiers of the HPA axis, coupled with its influence over cortical and subcortical brain structures. The endocannabinoid has been observed to govern the release of neurotransmitters from diverse neuronal populations, implying a universal mechanism that fine-tunes neuronal activity and consequently modulates both emotional and stress-related responses. Endocannabinoids further assume a pivotal function within brain reward mechanisms, primarily mediated by CB1 receptors distributed across diverse cerebral centers. Notably, these endocannabinoids partake in natural reward processes, as exemplified in aerobic exercise, by synergizing with the dopaminergic reward system. The genesis of this reward pathway can be traced to the ventral tegmental area, with dopamine neurons predominantly projecting to the nucleus accumbens, thereby inciting dopamine release in response to rewarding stimuli.

Fractional amplitude of low-frequency fluctuations associated with μ-opioid and dopamine receptor distributions in the central nervous system after high-intensity exercise bouts

Introduction

Dopaminergic, opiod and endocannabinoid neurotransmission are thought to play an important role in the neurobiology of acute exercise and, in particular, in mediating positive affective responses and reward processes. Recent evidence indicates that changes in fractional amplitude of low-frequency fluctuations (zfALFF) in resting-state functional MRI (rs-fMRI) may reflect changes in specific neurotransmitter systems as tested by means of spatial correlation analyses.

Methods

Here, we investigated this relationship at different exercise intensities in twenty young healthy trained athletes performing low-intensity (LIIE), high-intensity (HIIE) interval exercises, and a control condition on three separate days. Positive And Negative Affect Schedule (PANAS) scores and rs-fMRI were acquired before and after each of the three experimental conditions. Respective zfALFF changes were analyzed using repeated measures ANOVAs. We examined the spatial correspondence of changes in zfALFF before and after training with the available neurotransmitter maps across all voxels and additionally, hypothesis-driven, for neurotransmitter maps implicated in the neurobiology of exercise (dopaminergic, opiodic and endocannabinoid) in specific brain networks associated with "reward" and "emotion."

Results

Elevated PANAS Positive Affect was observed after LIIE and HIIE but not after the control condition. HIIE compared to the control condition resulted in differential zfALFF decreases in precuneus, temporo-occipital, midcingulate and frontal regions, thalamus, and cerebellum, whereas differential zfALFF increases were identified in hypothalamus, pituitary, and periaqueductal gray. The spatial alteration patterns in zfALFF during HIIE were positively associated with dopaminergic and μ-opioidergic receptor distributions within the 'reward' network.

Discussion

These findings provide new insight into the neurobiology of exercise supporting the importance of reward-related neurotransmission at least during high-intensity physical activity.

Effects of Bradykinin B2 Receptor Ablation from Tyrosine Hydroxylase Cells on Behavioral and Motor Aspects in Male and Female Mice

The kallikrein-kinin system is a versatile regulatory network implicated in various biological processes encompassing inflammation, nociception, blood pressure control, and central nervous system functions. Its physiological impact is mediated through G-protein-coupled transmembrane receptors, specifically the B1 and B2 receptors. Dopamine, a key catecholamine neurotransmitter widely distributed in the CNS, plays a crucial role in diverse physiological functions including motricity, reward, anxiety, fear, feeding, sleep, and arousal. Notably, the potential physical interaction between bradykinin and dopaminergic receptors has been previously documented. In this study, we aimed to explore whether B2R modulation in catecholaminergic neurons influences the dopaminergic pathway, impacting behavioral, metabolic, and motor aspects in both male and female mice. B2R ablation in tyrosine hydroxylase cells reduced the body weight and lean mass without affecting body adiposity, substrate oxidation, locomotor activity, glucose tolerance, or insulin sensitivity in mice. Moreover, a B2R deficiency in TH cells did not alter anxiety levels, exercise performance, or motor coordination in female and male mice. The concentrations of monoamines and their metabolites in the substantia nigra and cortex region were not affected in knockout mice. In essence, B2R deletion in TH cells selectively influenced the body weight and composition, leaving the behavioral and motor aspects largely unaffected.

Development and implementation of a Dependable, Simple, and Cost-effective (DSC), open-source running wheel in High Drinking in the Dark and Heterogeneous Stock/Northport mice

Maintaining healthy and consistent levels of physical activity (PA) is a clinically proven and low-cost means of reducing the onset of several chronic diseases and may provide an excellent strategy for managing mental health and related outcomes. Wheel-running (WR) is a well-characterized rodent model of voluntary PA; however, its use in biomedical research is limited by economical and methodical constraints. Here, we showcase the DSC (Dependable, Simple, Cost-effective), open-source running wheel by characterizing 24-h running patterns in two genetically unique mouse lines: inbred High Drinking in the Dark line 1 [iHDID-1; selectively bred to drink alcohol to intoxication (and then inbred to maintain phenotype)] and Heterogeneous Stock/Northport (HS/Npt; the genetically heterogeneous founders of iHDID mice). Running distance (km/day), duration (active minutes/day) and speed (km/hour) at 13-days (acute WR; Experiment 1) and 28-days (chronic WR; Experiment 2) were comparable to other mouse strains, suggesting the DSC-wheel reliably captures murine WR behavior. Analysis of 24-h running distance supports previous findings, wherein iHDID-1 mice tend to run less than HS/Npt mice in the early hours of the dark phase and more than HS/Npt in the late hours of dark phase/early light phase. Moreover, circadian actograms were generated to highlight the broad application of our wheel design across disciplines. Overall, the present findings demonstrate the ability of the DSC-wheel to function as a high-throughput and precise tool to comprehensively measure WR behaviors in mice.

Selectively breeding for high voluntary physical activity in female mice does not bestow inherent characteristics that resemble eccentric remodeling of the heart, but the mini-muscle phenotype does

Physical activity engagement results in a variety of positive health outcomes, including a reduction in cardiovascular disease risk partially due to eccentric remodeling of the heart. The purpose of this investigation was to determine if four replicate lines of High Runner mice that have been selectively bred for voluntary exercise on wheels have a cardiac phenotype that resembles the outcome of eccentric remodeling. Adult females (average age 55 days) from the 4 High Runner and 4 non-selected control lines were anaesthetized via vaporized isoflurane, then echocardiographic images were collected and analyzed for structural and functional differences. High Runner mice in general had lower ejection fractions compared to control mice lines (2-tailed p ​= ​0.023 6) and tended to have thicker walls of the anterior portion of the left ventricle (p ​= ​0.065). However, a subset of the High Runner individuals, termed mini-muscle mice, had greater ejection fraction (p ​= ​0.000 6), fractional shortening percentage (p ​< ​0.000 1), and ventricular mass at dissection (p ​< ​0.002 7 with body mass as a covariate) compared to non-mini muscle mice. Mice from replicate lines bred for high voluntary exercise did not all have inherent positive cardiac functional or structural characteristics, although a genetically unique subset of mini-muscle individuals did have greater functional cardiac characteristics, which in conjunction with their previously described peripheral aerobic enhancements (e.g., increased capillarity) would partially account for their increased V ˙ O2max.

Genetic polymorphisms in the serotonin, dopamine and opioid pathways influence social attention in rhesus macaques (Macaca mulatta)

Behaviour has a significant heritable component; however, unpicking the variants of interest in the neural circuits and molecular pathways that underpin these has proven difficult. Here, we present a comprehensive analysis of the relationship between known and new candidate genes from identified pathways and key behaviours for survival in 109 adult rhesus macaques (Macaca mulatta). Eight genes involved in emotion were analysed for variation at a total of nine loci. Genetic data were then correlated with cognitive and observational measures of behaviour associated with wellbeing and survival using MCMC-based Bayesian GLMM in R, to account for relatedness within the macaque population. For four loci the variants genotyped were length polymorphisms (SLC6A4 5-hydroxytryptamine transporter length-polymorphic repeat (5-HTTLPR), SLC6A4 STin polymorphism, Tryptophan 5-hydroxylase 2 (TPH2) and Monoamine oxidase A (MAOA)) whilst for the other five (5-hydroxytryptamine receptor 2A (HTR2A), Dopamine Receptor D4 (DRD4), Oxytocin receptor (OXTR), Arginine vasopressin receptor 1A (AVPR1a), Opioid receptor mu(μ) 1 (OPRM1)) SNPs were analysed. STin genotype, DRD4 haplotype and OXTR haplotype were significantly associated with the cognitive and observational measures of behaviour associated with wellbeing and survival. Genotype for 5-HTTLPR, STin and AVPR1a, and haplotype for HTR2A, DRD4 and OXTR were significantly associated with the duration of behaviours including fear and anxiety. Understanding the biological underpinnings of individual variation in negative emotion (e.g., fear and anxiety), together with their impact on social behaviour (e.g., social attention including vigilance for threat) has application for managing primate populations in the wild and captivity, as well as potential translational application for understanding of the genetic basis of emotions in humans.

Transcriptomic analysis reveals novel molecular signaling networks involved in low voluntary running behavior after AP-1 inhibition

Understanding the neuro-molecular mechanisms that mediate the quantity of daily physical activity (PA) level is of medical significance, given the tremendous health benefits associated with greater physical activity. Here, we examined the effects of intra-nucleus accumbens (NAc) inhibition of activator protein-1 (AP-1), an important transcriptional factor downstream of cAMP response element binding protein (CREB; a reward-related transcriptional regulator), on voluntary wheel running behavior in wild-type (WT) and low voluntary running (LVR) female rats. Transcriptome analysis of the nucleus accumbens (NAc; a brain region critical for PA reward and motivation) was performed to further determine molecular responses to intra-NAc AP-1 inhibition in these rat lines. Within WT rats, intra-NAc AP-1 inhibition caused a significant decrease in overnight running distance in comparison to control rats (p = 0.009). Transcriptomic and bioinformatic analysis in WT rats identified involvement of gene products that regulate cellular proliferation and development, which were cellular processes regulated by AP-1. In contrast to above decreased WT distances, intra-NAc AP-1 inhibition in LVR rats increased nightly running distance in comparison to LVR control rats (p = 0.0008). Further analysis identified gene products that are associated with regulating intracellular Ca²⁺ homeostasis, calcium ion binding and neuronal excitability. In short, our study aims to gain a comprehensive understanding of transcriptional profile that was due to AP-1 inhibition in NAc, in which it could not only enhance the knowledge regarding molecular regulatory loops within NAc for modulating voluntary running behavior, but also provide further insights into molecular targets for future investigations.

Duration- and sex-dependent neural circuit control of voluntary physical activity

RATIONALE

Exercise participation remains low despite clear benefits. Rats engage in voluntary wheel running (VWR) that follows distinct phases of acquisition, during which VWR escalates, and maintenance, during which VWR remains stable. Understanding mechanisms driving acquisition and maintenance of VWR could lead to novel strategies to promote exercise. The two phases of VWR resemble those that occur during operant conditioning and, therefore, might involve similar neural substrates. The dorsomedial (DMS) dorsal striatum (DS) supports the acquisition of operant conditioning, whereas the dorsolateral striatum (DLS) supports its maintenance.

OBJECTIVES

Here we sought to characterize the roles of DS subregions in VWR. Females escalate VWR and operant conditioning faster than males. Thus, we also assessed for sex differences.

METHODS

To determine the causal role of DS subregions in VWR, we pharmacologically inactivated the DMS or DLS of adult, male and female, Long-Evans rats during the two phases of VWR. The involvement of DA receptor 1 (D1)-expressing neurons in the DS was investigated by quantifying cfos mRNA within this neuronal population.

RESULTS

We observed that, in males, the DMS and DLS are critical for VWR exclusively during acquisition and maintenance, respectively. In females, the DMS is also critical only during acquisition, but the DLS contributes to VWR during both VWR phases. DLS D1 neurons could be an important driver of VWR escalation during acquisition.

CONCLUSIONS

The acquisition and maintenance of VWR involve unique neural substrates in the DS that vary by sex. Results reveal targets for sex-specific strategies to promote exercise.

Moderate physical activity alters the estimation of time, but not space

Moderate physical activity can influence cognitive functions and visual cortical activity. However, little is known about the effects of exercise on fundamental perceptual domains, such as spatial and temporal representation. Here we tackled this issue by testing the impact of physical activity on a temporal estimation task in a group of adult volunteers in three different conditions: (1) in a resting condition (baseline), (2) during moderate physical activity (cycling in place – PA), and (3) approximately 15 to 20 min following the physical activity phase, in which participants were seated and returned to a regular heart rate (POST). We show that physical activity specifically impacts time perception, inducing a consistent overestimation for durations in the range of milliseconds. Notably, the effect persisted in the POST session, ruling out the main contribution of either heart rate or cycling rhythmicity. In a control experiment, we found that spatial perception (distance estimation) was unaffected by physical activity, ruling out a major contribution of arousal and fatigue to the observed temporal distortion. We speculate that physical exercise might alter temporal estimation either by up-regulating the dopaminergic system or modulating GABAergic inhibition.

Experimental longitudinal evidence for causal role of social media use and physical activity in COVID-19 burden and mental health

Aim

The COVID-19 outbreak has severely impacted people's mental health. The present experimental study investigated how to reduce this negative effect by a combination of two interventions.

Subject and methods

Participants (N total = 642) were users of social media in Germany. For two weeks, the social media group (N = 162) reduced its social media use (SMU) by 30 minutes daily, the physical activity group (N = 161) increased its physical activity by 30 minutes daily, the combination group (N = 159) followed both instructions, and the control group (N = 160) did not get specific instructions. Online surveys assessed variables of SMU, physical activity, mental health, COVID-19 burden, and lifestyle at six measurement time points up to six months after the intervention.

Results

In the experimental groups, (addictive) SMU, depression symptoms, and COVID-19 burden decreased, while physical activity, life satisfaction, and subjective happiness increased. All effects were stronger and more stable in the combination group in the longer-term. Smoking behavior decreased in the social media group only.

Conclusion

Thus, the conscious combination of less SMU and more physical activity leads causally to more psychological resilience against negative pandemic impacts and to higher levels of mental health over six months. Prevention programs could improve their effectiveness by integrating the time- and cost-efficient interventions - separately or in combination.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10389-022-01751-x.

Let’s Get Physical: Physical Activity as a Team Intervention at Work

The purpose of this article is to conceptualize a novel theoretical occurrence—team physical activity (PA)—and its relevance for researchers and organizations. By building a testable model of the consequences and contingencies of team PA, we integrate the science of teamwork with the scholarly domain of employee health and well-being. Hence, we clarify the construct of team PA, present a three-dimensional typology, and outline a model drawing on neuroscience, positive organizational behavior, and teams research. Our propositions and subsequent discussion proffer an outline of potential benefits for organizations when they increase the utility and frequency of team PA. We also suggest ways in which researchers can advance scholarship in this area.

Associations between aerobic exercise and dopamine-related reward-processing: Informing a model of human exercise engagement

Endurance or aerobic exercise has many physical and mental health benefits, but less is known about the specific impact that cardiovascular activity may have on dopamine-associated brain circuits involved in reward processing and mood regulation in humans. Understanding such effects will help to explain individual differences in both exercise uptake and maintenance. This study evaluated neural response to a classical taste-conditioning reward prediction error task with the use of functional magnetic resonance imaging, along with data on self-reported aerobic exercise among healthy young adult females (N = 111). Results indicated positive associations between reported aerobic exercise and regional brain response that remained significant after multiple comparison correction for the right medial orbital frontal cortex response to unexpected sucrose receipt (r = 0.315, p = .0008). The medial orbitofrontal cortex is implicated in reward and outcome value computation and the results suggest that aerobic exercise may strengthen this circuitry, or reciprocally, higher orbitofrontal cortical activity may reinforce exercise behavior. The findings aid in developing a model of how exercise engagement can modify reward-circuit function and could be used therapeutically in conditions associated with altered brain salience response.

Dopaminergic and glutamatergic biomarkers disruption in addiction and regulation by exercise: a mini review

INTRODUCTION

Drug addiction is associated with disruption of a multitude of biomarkers in various brain regions, particularly in the reward center. The most pronounced are dopaminergic and glutamatergic biomarkers, which are affected at various levels. Neuropathological changes in biomarkers alter the homeostasis of the glutamatergic and dopaminergic nervous systems and promote addiction-associated characteristics such as repeated intake, maintenance, withdrawal, reinstatement, and relapse. Exercise has been shown to have a buffering effect on such biomarkers and reverse the effects of addictive substances.

METHODS

A review of the literature searched in PubMed, examining drug addiction and physical exercise in relation to dopaminergic and glutamatergic systems at any of the three biomarker levels (i.e., neurotransmitter, receptor, or transporter).

RESULTS

We review the collective impact of addictive substances on the dopaminergic and glutamatergic systems and the beneficial effect of exercise in terms of reversing the damage to these systems. We propose future directions, including implications of exercise as an add-on therapy, substance use disorder (SUD) prognosis and diagnosis and designing of optimized exercise and pharmaceutical regimens based on the aforementioned biomarkers.

CONCLUSION

Exercise is beneficial for all types of drug addiction at all stages, by reversing molecular damages caused to dopaminergic and glutamatergic systems.

Analysis of Selected Variants of DRD2 and ANKK1 Genes in Combat Athletes

The level of physical activity is conditioned by many different factors, including, among others, the personality traits of a person. Important is the fact that personality traits are a moderately heritable factor and on the basis of the analysis of several genes, various lifetime outcomes can be predicted. One of the most important pathways influencing personality traits is connected to the dopaminergic system; hence, we decided to analyze the DRD2 PROM. rs1799732, DRD2 rs1076560, DRD2 Tag1D rs1800498, DRD2 Ex8 rs6276, DRD2Tag1B rs1079597 and ANKK1 Tag1A rs180049. The research group included 258 male athletes (mean age = 26.02; SD = 8.30), whereas the control group was 284 healthy male volunteers matched for age (mean age = 22.89; SD = 4.78), both of Caucasian origin and without history of substance dependency or psychosis. Genomic DNA was extracted from venous blood using standard procedures. Genotyping was conducted with the real-time PCR method. Differences in the frequency of the DRD2Tag1B rs1079597 gene polymorphism were found between people practicing combat sports and the control group, and the DRD2 PROM. rs1799732, DRD2 rs1076560, DRD2 Tag1D rs1800498, DRD2 Ex8 rs6276, DRD2Tag1B rs1079597 and ANKK1 Tag1A rs1800497 genotypes and allele frequencies in the studied sample did not differ between the analyzed groups. Hence, we considered these polymorphic places as an interesting area for the further search for unambiguous associations between personality traits and attitude towards physical effort.

Comparing the reinforcing value of high intensity interval training versus moderate intensity aerobic exercise in sedentary adults

Exercise is a reinforcer for both animals and humans, as they will work progressively harder to gain access for the opportunity to exercise. Exercise activates brain reward pathways similar to drugs of abuse, and the magnitude of the reinforcing value of exercise is a predictor of exercise behavior. The majority of research on exercise reinforcement has studied moderate intensity aerobic exercise (MIAE) or resistance training. There is limited research on the relative reinforcing value (RRV) of high intensity interval training (HIIT), which is often reported to be a preferred form of exercise in comparison to MIAE. Experiment 1 was a pilot study of 20 sedentary females designed to compare the reliability of differences in RRV_HIIT vs RRV_MIAE over two sessions, assess protocols comparing different volumes of HIIT in comparison to MIAE, and estimate sample sizes needed for a fully powered study to assess which type of exercise protocol was a better substitute for a highly liked sedentary activity. Experiment 2 studied 44 participants to assess whether HIIT or MIAE would be better substitutes for highly liked sedentary activities. Experiment 1 showed that measures of RRV_HIIT or RRV_MIAE were reliable, and that volume of HIIT did not influence RRV_HIIT, even if it was of equal amount or duration to MIAE. Experiment 2 showed that HIIT was a more preferred substitute for sedentary behaviors than MIAE. Predictors of RRV_MIAE were liking of MIAE and pleasantness of affect post MIAE. These results suggest inactive people may find interval training to be more reinforcing than MIAE, and may be more likely to adopt and maintain an exercise program involving HIIT rather than MIAE. The next stage of research should be to understand how to sensitize the RRV of exercise to motivate sedentary people to be more active.

The Role of Dopamine Receptor D2 in Bridging the Intention-Behavior Gap in Sport Participation

Previous studies have identified that a behavior can occur through the strongest predictor intention, but there is a gap between intention and behavior. Dopamine receptor D2 (DRD2) is known to account for a variance in sporting behaviors in human and animal subjects. However, the relationship between DRD2 and sport participation has been poorly studied, and the limited available reports are inconsistent. The present study was performed to examine the impact of DRD2 on sport participation among Korean university students based on the integrated behavioral model (IBM). Data were collected from enrolled university students in Seoul (N = 45). Participants answered survey questions first, and then they gave investigators their hair to provide DNA information (i.e., the A1 allele of DRD2). DRD2 had a significant effect on sport participation, but only in male students. Male students who carried the A1 allele of DRD2 significantly participated in 105.10 min more sporting activities than male students who did not. Moreover, the effect of intention on sport participation was significantly decreased when considering DRD2. Despite the small sample size, the results of this study could be a preliminary case for a larger study and indicate the direction of future research. Our results suggest that DRD2 may have played an important role as the “actual skill” shown in the IBM.

The Protective Roles of Exercise and Maintenance of Daily Living Routines for Chinese Adolescents During the COVID-19 Quarantine Period

PURPOSE

Adolescents are particularly vulnerable during the COVID-19 quarantine periods and may be at risk for developing psychological distress symptoms that extend beyond a crisis, including depression. This study examined adolescents' postquarantine depressive symptoms associated with pandemic stressors. The primary aim was to identify potential protective factors that may buffer the association between the presence of COVID-19 cases in adolescents' communities and their postquarantine depressive symptoms.

METHODS

Adolescents from public schools were recruited from Zhengzhou city, Henan, China (N = 1,487, M_age=13.14 years, 50% girls). Adolescents reported the presence of confirmed or suspected COVID-19 cases in their communities, their daily activities and routines during the 2-month quarantine period, and depressive symptoms after the quarantine period.

RESULTS

The presence of cases in adolescents' communities during the quarantine contributed to more depressive symptoms in adolescents after the quarantine. This association was buffered by adolescents' spending more time on physical activities and better maintenance of daily living routines during the quarantine period. The presence of community infection was also more strongly associated with depressive symptoms in older adolescents.

CONCLUSIONS

The presence of COVID-19 cases in communities contributed to adolescents' poorer mental health, and the association was stronger for older adolescents. Spending time on physical activities and maintaining daily living routines during the quarantine appear to be practical strategies that can be used by adolescents to mitigate the association between pandemic stressors and their diminishing mental health.

Social isolation is closely linked to a marked reduction in physical activity in male mice

The effects of social isolation on an individual's behavior is an important field of research, especially as public health officials encourage social distancing to prevent the spread of pandemic disease. In this study we evaluate the effects of social isolation on physical activity in mice. Utilizing a pixel-based tracking system, we continuously monitored the movement of isolated mice compared with paired cage mates in the home cage environment. We demonstrate that mice that are socially isolated dramatically decrease their movement when separated from their cage mate, and especially in the dark cycle, when mice are normally most active. When isolated mice are re-paired with their original cage mate, this effect is reversed, and mice return to their prior levels of activity. These findings suggest a close link between social isolation and physical activity, and are of particular interest in the wake of coronavirus disease 2019, when many are forced into isolation. Social isolation may affect an individual's overall activity levels in humans too, which may have unintended effects on health that deserve further consideration.

Acute exercise enhances fear extinction through a mechanism involving central mTOR signaling

Impaired fear extinction, combined with the likelihood of fear relapse after exposure therapy, contributes to the persistence of many trauma-related disorders such as anxiety and post-traumatic stress disorder. Identifying mechanisms to aid fear extinction and reduce relapse could provide novel strategies for augmentation of exposure therapy. Exercise can enhance learning and memory and augment fear extinction of traumatic memories in humans and rodents. One factor that could contribute to enhanced fear extinction following exercise is the mammalian target of rapamycin (mTOR). mTOR is a translation regulator involved in synaptic plasticity and is sensitive to many exercise signals such as monoamines, growth factors, and cellular metabolism. Further, mTOR signaling is increased after chronic exercise in brain regions involved in learning and emotional behavior. Therefore, mTOR is a compelling potential facilitator of the memory-enhancing and overall beneficial effects of exercise on mental health.The goal of the current study is to test the hypothesis that mTOR signaling is necessary for the enhancement of fear extinction produced by acute, voluntary exercise. We observed that intracerebral-ventricular administration of the mTOR inhibitor rapamycin reduced immunoreactivity of phosphorylated S6, a downstream target of mTOR, in brain regions involved in fear extinction and eliminated the enhancement of fear extinction memory produced by acute exercise, without reducing voluntary exercise behavior or altering fear extinction in sedentary rats. These results suggest that mTOR signaling contributes to exercise-augmentation of fear extinction.

Should Couch Potatoes Be Encouraged to Use Transcranial Direct Current Stimulation?

A very high percentage of the world population doesn’t exercise enough and, as a consequence, is at high risk of developing serious health conditions. Physical inactivity paired with a poor diet is the second cause of death in high income countries. In this paper, I suggest that transcranial direct stimulation (tDCS) holds promise for “couch potatoes” because it could be used to make them more active, without causing any major side-effect. I also argue that other, less safe, tools could be used to achieve the goal of decreasing physical inactivity, insofar as they have overall fewer side-effects than physical inactivity.

The role of nucleus accumbens CREB attenuation in rescuing low voluntary running behavior in female rats

Given the integral role of nucleus accumbens (NAc) cAMP response element binding protein (CREB) activity in motivational processes, the goal of the current study was to determine whether blunting chronic NAc CREB activity could rescue the low physical activity motivation of female, low voluntary running (LVR) rats. NAc CREB phosphorylation is elevated in these rats, a state previously attributed to deficits in reward valuation. It was recently shown that overexpression of the upstream CREB inhibitor, protein kinase inhibitor alpha (PKIα), increased LVR nightly running by ~threefold. Therefore, the current study addresses the extent to which NAc CREB attenuation influences female LVR and wild-type (WT) wheel-running behavior. Inducible reductions in NAc neuronal activity using Gi-coupled hM4Di DREADDs increased running behavior in LVR, but not in WT, rats. Similarly, site-directed pharmacological inhibition of NAc CREB activity significantly increased LVR nightly running distance and time by ~twofold, with no effect in WT rats. Finally, environmentally enriched LVR rats exhibit higher levels of running compared to socially isolated rats in what appeared to be a CREB-related manner. Considering the positive outcomes of upstream CREB modulation and environmental enrichment on LVR behavior, we believe that blunting NAc CREB activity has the neuromolecular potential to partially reverse low physical activity motivation, as exemplified by the LVR model. The positive physical activity outcome of early life enrichment adds translatable value to human childhood enrichment and highlights its importance on motivational processes later in life.

β-endorphin response to aerobic and anaerobic exercises in Wistar male rats

BACKGROUND Physical exercise is strongly associated with the release of β-endorphin. It is assumed that the type and intensity of physical exercise contributes to the release of β-endorphin. This study aimed to compare levels of β-endorphin in brain tissue in response to aerobic and anaerobic physical exercise. METHODS This study was an experimental laboratory study using 35 male Wistar rats divided into one control group and two physical exercise treatment groups: aerobic and anaerobic. Physical exercise was conducted on an animal treadmill running at aspeed of 20 m/min for 30 min of aerobic exercise and 35 m/min with 1-min intervals every 5 min for 20 min for anaerobic exercises. Each aerobic and anaerobic exercise group was furtherly classified into three subgroups (1×/week, 3×/week, and 7×/week). β-endorphin levels were determined using enzyme-linked immunosorbent assay. The data were analyzed using independent t-test and one-way analysis of variance. RESULTS The highest mean of β-endorphin level was found in the weekly exercise (54.45 [1.41] pg/ml) of aerobic exercise group and daily exercise (70.50 [11.67] pg/ml) of anaerobic exercise group. Mean of β-endorphin level in control group was 33.34 (3.54) pg/ml. A significant increased of β-endorphin mean level (p<0.001) was found in all aerobic and anaerobic exercise groups except the aerobic exercise 7×/week group(37.37 [6.30] pg/ml) compared to control. CONCLUSIONS Both aerobic and anaerobic physical exercise conducted for 6 weeks could increase the level of β-endorphin in brain tissue.

Conditioned place preference for cocaine and methylphenidate in female mice from lines selectively bred for high voluntary wheel-running behavior

Behavioral addictions can come in many forms, including overeating, gambling and overexercising. All addictions share a common mechanism involving activation of the natural reward circuit and reinforcement learning, but the extent to which motivation for natural and drug rewards share similar neurogenetic mechanisms remains unknown. A unique mouse genetic model in which four replicate lines of female mice were selectively bred (>76 generations) for high voluntary wheel running (High Runner or HR lines) alongside four non-selected control (C) lines were used to test the hypothesis that high motivation for exercise is associated with greater reward for cocaine (20 mg/kg) and methylphenidate (10 mg/kg) using the conditioned place preference (CPP) test. HR mice run ~three times as many revolutions/day as C mice, but the extent to which they have increased motivation for other rewards is unknown. Both HR and C mice displayed significant CPP for cocaine and methylphenidate, but with no statistical difference between linetypes for either drug. Taken together, results suggest that selective breeding for increased voluntary running has modified the reward circuit in the brain in a way that increases motivation for running without affecting cocaine or methylphenidate reward.

Exercise improves high-fat diet- and ovariectomy-induced insulin resistance in rats with altered hepatic fat regulation

A high-fat diet (HFD) and loss of endogenous estrogens increases the risk for type 2 diabetes (T2D) and insulin resistance. Although exercise is known to prevent and manage insulin resistance, the cellular mechanisms remain largely unknown, especially in the context of a combined HFD and endogenous estrogen loss via ovariectomy (OVX). This study uses female Wistar rats to assess the effect of diet, endogenous estrogens, an exercise on insulin resistance, serum hormones, hepatic AMPK, hepatic regulators of fat metabolism, and expression of signaling molecules of the brain reward pathway. The combination of the HFD/OVX increased the homeostatic model assessment of insulin resistance (HOMA-IR), the glucose-insulin (G-I) index, and the serum adiponectin and leptin values, and exercise decreased these factors. The combination of the HFD/OVX decreased hepatic pAMPK, and exercise restored hepatic pAMPK, an important regulator of fat and glucose metabolism. Furthermore, consumption of the HFD by rats with intact ovaries (and endogenous estrogens) did not result in these drastic changes compared to intact rats fed a standard diet, suggesting that the presence of estrogens provides whole body benefits. Additionally, the HFD decreased the hepatic protein expression of acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS), two proteins involved in de novo lipid synthesis and increased the hepatic protein expression of lipoprotein lipase (LPL), a protein involved in fat storage. Finally, exercise increased mRNA expression of the dopamine D₂ receptor and tyrosine hydroxylase in the dopaminergic neuron cell body region of the ventral tegmental area, which is a key component of the brain reward pathway. Overall, this study demonstrates that exercise prevents insulin resistance even when a HFD is combined with OVX, despite hepatic changes in ACC, FAS, and LPL.

Incentive sensitization for exercise reinforcement to increase exercise behaviors

Individuals can be sensitized to the reinforcing effects of exercise, although it is unknown if this process increases habitual exercise behavior. Sedentary men and women (body mass index: 25-35 kg/m², N = 52) participated in a 12-week aerobic exercise intervention. Exercise reinforcement was determined by how much work was performed for exercise relative to a sedentary alternative in a progressive ratio schedule task. Habitual physical activity was assessed via accelerometry. Post-intervention increases in exercise reinforcement predicted increases in physical activity bouts among those who expended over 2000 kcal per week in exercise and who compensated for less than 50 percent of their exercise energy expenditure.

Aging Fits the Disease Criteria of the International Classification of Diseases

The disease criteria used by the World Health Organization (WHO) were applied to human biological aging in order to assess whether aging can be classified as a disease. These criteria were developed for the 11th revision of the International Classification of Diseases (ICD) and included disease diagnostics, mechanisms, course and outcomes, known interventions, and linkage to genetic and environmental factors. RESULTS: Biological aging can be diagnosed with frailty indices, functional, blood-based biomarkers. A number of major causal mechanisms of human aging involved in various organs have been described, such as inflammation, replicative cellular senescence, immune senescence, proteostasis failures, mitochondrial dysfunctions, fibrotic propensity, hormonal aging, body composition changes, etc. We identified a number of clinically proven interventions, as well as genetic and environmental factors of aging. Therefore, aging fits the ICD-11 criteria and can be considered a disease. Our proposal was submitted to the ICD-11 Joint Task force, and this led to the inclusion of the extension code for "Ageing-related" (XT9T) into the "Causality" section of the ICD-11. This might lead to greater focus on biological aging in global health policy and might provide for more opportunities for the new therapy developers.

The therapeutic potential of exercise for neuropsychiatric diseases: A review

Exercise is known to have a myriad of health benefits. There is much to be learned from the effects of exercise and its potential for prevention, attenuation and treatment of multiple neuropsychiatric diseases and behavioral disorders. Furthermore, recent data and research on exercise benefits with respect to major health crises, such as, that of opioid and general substance use disorders, make it very important to better understand and review the mechanisms of exercise and how it could be utilized for effective treatments or adjunct treatments for these diseases. In addition, mechanisms, epigenetics and sex differences are examined and discussed in terms of future research implications.

Medial preoptic estrogen receptor-beta blunts the estrogen receptor-alpha mediated increases in wheel-running behavior of female rats

Estrogens are believed to enhance rodent voluntary wheel-running through medial preoptic (mPOA) estrogen receptor α (ERα) signaling, with little role attributed to estrogen receptor β (ERβ). Systemic ERβ activation has been shown to mitigate ERα driven increases in wheel-running. Therefore, the present goal was to determine whether ERβ signaling in the mPOA plays a similar modulatory role over ERα. We utilized outbred wild-type (WT) and rats selectively bred for low voluntary running (LVR) behavior to address whether mPOA ERβ signaling blunts ERα driven wheel-running behavior and immediate-early gene (Fos, Zif268, and Homer1) mRNA induction. Further, we addressed baseline mPOA mRNA expressions and circulating 17β-estradiol levels between female WT and LVR rats. Following ovariectomy, WT rats reduced running behavior ∼40 %, with no effect in LVR rats. Intra-medial preoptic injection of the ERα-agonist propylpyrazoletriol (PPT) increased wheel-running ∼3.5-fold in WT rats, while injections of the ERβ-agonist diarylpropionitrile (DPN) or a combination of the two agonists had no effect. Similarly, ERα-agonism (PPT) increased Fos and Homer1 induction ∼3-fold in WT and LVR isolated mPOA neurons, with no effect of the ERβ-agonist DPN alone or in combination with PPT, suggesting medial-preoptic ERβ activity may blunt ERα signaling. LVR rats exhibited higher mPOA mRNA expressions of Esr1, Esr2 and Cyp19a1, lower normalized uterine wet weights and lower 17β-estradiol plasma levels compared to WT, suggesting their low running may be due to low circulating estrogen levels. Collectively, these findings highlight mPOA ERβ as a potential neuro-molecular modulator of the estrogenic control of wheel-running behavior.

High Fat Diet Suppresses Peroxisome Proliferator-Activated Receptors and Reduces Dopaminergic Neurons in the Substantia Nigra

Although several epidemiologic and animal studies have revealed correlations between obesity and neurodegenerative disorders, such as Parkinson disease (PD), the underlying pathological mechanisms of obesity-induced PD remain unclear. Our study aimed to assess the effect of diet-induced obesity on the brain dopaminergic pathway. For five months, starting from weaning, we gave C57BL/6 mice a high-fat diet (HFD) to generate an obese mouse model and investigate whether the diet reprogrammed the midbrain dopaminergic system. Tyrosine hydroxylase staining showed that the HFD resulted in fewer dopaminergic neurons in the substantia nigra (SN), but not the striatum. It also induced neuroinflammation, with increased astrogliosis in the SN and striatum. Dendritic spine density in the SN of HFD-exposed mice decreased, which suggested that prolonged HFD altered dopaminergic neuroplasticity. All three peroxisome proliferator-activated receptor (PPAR) subtype (PPAR-α, PPAR-β/δ, PPAR-γ) levels were significantly reduced in the SN and the ventral tegmental area of HFD mice when compared to those in controls. This study showed that a prolonged HFD induced neuroinflammation, suppressed PPAR levels, caused degeneration of midbrain dopaminergic neurons, and resulted in symptoms reminiscent of human PD. To our knowledge, this is the first study documenting the effects of an HFD on PPARs in dopaminergic neurons.

Increasing the Reinforcing Value of Exercise in Overweight Adults

Objectives: This study determined whether a moderate- or high-dose exercise program increases exercise reinforcement. Increasing the relative reinforcing value of exercise (RRV_exercise; i.e., incentive sensitization of exercise) may increase the usual physical activity (PA) participation. Preference and/or tolerance for the intensity of exercise was also assessed.

Design: Sedentary men and women (body mass index, BMI: 25–35 kg/m²) were randomized into parallel exercise training groups expending either 300 (n = 18) or 600 (n = 18) kcal/exercise session, five sessions/week, for 12 weeks.

Methods: The RRV_exercise was determined by how much work was performed for exercise relative to a sedentary alternative in a progressive ratio schedule task. Preference and tolerance for exercise intensity were determined by questionnaire.

Results: RRV_exercise increased (P < 0.05) in both groups. Exercise reinforcement, defined as the amount of work completed for exercise without taking sedentary activity into account, increased (P < 0.01) in the 600 kcal group only. Preference and tolerance for exercise intensity increased (P < 0.01) in both groups, which predicted increases in RRV_exercise.

Conclusion: Expending 300 or 600 kcal, 5 days/week increases RRV_exercise, while 600 kcal, 5 days/week may be needed to increase exercise reinforcement.

Physical Activity and Brain Health

Physical activity (PA) has been central in the life of our species for most of its history, and thus shaped our physiology during evolution. However, only recently the health consequences of a sedentary lifestyle, and of highly energetic diets, are becoming clear. It has been also acknowledged that lifestyle and diet can induce epigenetic modifications which modify chromatin structure and gene expression, thus causing even heritable metabolic outcomes. Many studies have shown that PA can reverse at least some of the unwanted effects of sedentary lifestyle, and can also contribute in delaying brain aging and degenerative pathologies such as Alzheimer’s Disease, diabetes, and multiple sclerosis. Most importantly, PA improves cognitive processes and memory, has analgesic and antidepressant effects, and even induces a sense of wellbeing, giving strength to the ancient principle of “mens sana in corpore sano” (i.e., a sound mind in a sound body). In this review we will discuss the potential mechanisms underlying the effects of PA on brain health, focusing on hormones, neurotrophins, and neurotransmitters, the release of which is modulated by PA, as well as on the intra- and extra-cellular pathways that regulate the expression of some of the genes involved.

The effect of monoamines reuptake inhibitors on aerobic exercise performance in bank voles from a selection experiment

Exercise performance depends on both physiological abilities (e.g., muscle strength) and behavioral characteristics (e.g., motivation). We tested the hypothesis that evolution of increased aerobic exercise performance can be facilitated by evolution of neuropsychological mechanisms responsible for motivation to undertake physical activity. We used a unique model system: lines of bank voles Myodes glareolus selected for high swim-induced aerobic metabolism ("aerobic" A lines). In generation 21, voles from the 4 A lines achieved a 57% higher "voluntary maximum" swim-induced aerobic metabolism (VO2swim) than voles from 4 unselected, "control" C lines. In C lines, VO2swim was 9% lower than the maximum forced-exercise aerobic metabolism (VO2run; P = 0.007), while in A lines it was even higher than VO2run, although not significantly (4%, P = 0.15). Thus, we hypothesized that selection changed both the aerobic capacity and the neuronal mechanisms behind motivation to undertake activity. We investigated the influence of reuptake inhibitors of dopamine (DARI), serotonin (SSRI), and norepinephrine (NERI) on VO2swim. The drugs decreased VO2swim both in C and A lines (% decrease compared with saline: DARI 8%, P < 0.001; SSRI 6%, P < 0.001; NERI 8%, P < 0.001), but the proportional response differed between selection directions only for NERI (stronger effect in C lines: P = 0.008) and the difference was marginally non-significant for SSRI (P = 0.07) and DARI (P = 0.06). Thus, the results suggest that all the 3 monoamines are involved in signaling pathways controlling the motivation to be active and that norepinephrine could have played a role in the evolution of increased aerobic exercise performance in our animal model.

A pragmatic randomised controlled trial of preferred intensity exercise in depressed adult women in the United Kingdom: secondary analysis of individual variability of depression

BACKGROUND

This study is a secondary analysis of the trial by Callaghan et al. (2011), which reported higher antidepressant effects for preferred intensity (n = 19) vs. prescribed intensity (n = 19) exercise of three sessions/week over four weeks in depressed women. In particular, the present study sought to examine whether greater clinically significant individual change/recovery was observed in the preferred compared to the prescribed exercise group.

METHODS

The reliable change index and the C_cutoff score criteria described by Jacobson and Truax (1991) were employed to determine clinical significance. These criteria examined if individual change in depression scores from pre- to post-intervention in the preferred intensity group were statistically significant beyond the standard error of difference derived from the active comparator prescribed group, and subsequently within a normal population range. Patients fulfilling the first or both criteria were classified as improved or recovered, respectively.

RESULTS

Post-intervention depression scores of six patients in the preferred intensity exercise group (32%) demonstrated statistically reliable improvement (p < 0.05) and recovery. Half of this subgroup started as moderately depressed. No patient demonstrated a reliable deterioration in depression. Due to a small sample size, it was impossible to determine whether patients on psychiatric medication or medication-free patients were equally benefited from preferred intensity exercise. Thirteen patients in the preferred intensity group (68%) displayed non-statistically significant change in post-intervention depression scores (p > 0.05), although eight of them showed a non-significant improvement in post-intervention depression scores and three could not technically show an improvement in depression due to floor effects (baseline depression within normal range).

CONCLUSIONS

Preferred intensity exercise of three sessions/week over four weeks led almost a third of the patients to record scores consistent with recovery from depression. Health professionals may consider that short-term preferred intensity exercise provides clinically significant antidepressant effects comparing favourably to exercise on prescription.

Effect of amphetamine dose on wheel-running functioning as reinforcement or operant behavior on a multiple schedule of reinforcement

Does the effect of amphetamine on behavior (wheel running) differ depending on the functional role (operant, reinforcement) of that behavior? This study addressed this question using a multiple schedule of reinforcement in which wheel running served as reinforcement for lever pressing in one component and as operant behavior for sucrose reinforcement in the other component. Seven female Long-Evans rats were exposed to a multiple schedule in which pressing a lever on a variable ratio 10 schedule produced the opportunity to run for 15 revolutions in one component and running 15 revolutions produced a drop of 15% sucrose solution in the other component. Doses of 0.5, 1.0, and 2.0 mg/kg D-amphetamine were administered by intraperitoneal injection 20 min prior to a session. As amphetamine dose increased, wheel running decreased in both components - showing no evidence that the effect of the drug on wheel running depended on the function of wheel activity. Notably, lever pressing for wheel-running reinforcement also decreased with amphetamine dose. Drug dose increased the initiation of operant lever pressing, but not the initiation of operant wheel running. We propose that amphetamine dose had common effects on wheel running regardless of its function (reinforcement vs. operant) because wheel-running generates automatic reinforcement and the automatic-reinforcement value of wheel activity is modulated by drug dose.

The effect of voluntary wheel running on 129/SvEvTac and C3H/Ibg alcohol consumption

The mesolimbic dopaminergic reward pathway is activated by both alcohol and exercise, suggesting exercise as a possible treatment or preventative method for alcohol-use disorders (AUDs). Prior studies conducted in our lab have demonstrated the hedonic substitution of voluntary alcohol consumption for voluntary wheel running in female C57Bl/6Ibg mice, and a trend in male C57Bl/6Ibg mice. Given the important contribution of genetic background on AUDs, this study aims to assess the effects of voluntary wheel running on voluntary alcohol consumption in two moderate alcohol-consuming strains of mice, C3H/Ibg and 129/SvEvTac. Contrary to our previous studies conducted in C57Bl/6Ibg mice, 129/SvEvTac and male C3H/Ibg mice housed without a wheel consumed significantly more alcohol than mice housed with a free or locked wheel. This suggests that 129/SvEvTac and male C3H/Ibg mice are reducing their alcohol consumption due to an enriched environment and not exercise. Interestingly, the three groups of female C3H/Ibg mice (free wheel, locked wheel, no wheel) did not significantly differ in alcohol consumption, suggesting sex-specific differences in C3H/Ibg mice. In addition, genetic and sex effects were observed for running phenotypes in the presence of alcohol. Female 129/SvEvTac and C57Bl/6Ibg mice ran longer distances than male mice, whereas male and female C3H/Ibg mice did not differ in distance run. C3H/Ibg and female 129/SvEvTav mice with access only to water ran longer distances than mice with access to both alcohol and water. However, this effect was not observed in C57Bl/6Ibg or male 129/SvEvTac mice. The results of this mouse model highlight the importance of genetic background and sex on an animal's response to exercise as an enrichment to reduce voluntary alcohol consumption.

Inducing incentive sensitization of exercise reinforcement among adults who do not regularly exercise-A randomized controlled trial

Background

Increasing exercise reinforcement, or decreasing sedentary reinforcement, may reduce sedentary activity and promote habitual exercise. Repeated exposures to a reinforcer may increase its reinforcing value (i.e., incentive sensitization). It is not yet known whether incentive sensitization occurs for exercise or factors associated with incentive sensitization for exercise reinforcement. The purpose was to determine whether exercise exposures increase exercise reinforcement relative to a sedentary alternative and whether this sensitization of exercise reinforcement would alter physical or sedentary behavior. This work also determined whether exercise dose, intensity, and preference and tolerance for exercise intensity were associated with incentive sensitization of exercise.

Methods

104 sedentary men and women were randomized to exercise training groups with 89 completing the study. Groups included exercise exposures of 150 (n = 35) or 300 kcal/session (n = 34), 3 sessions/week for 6 weeks, or a non-exercise control group (n = 35). Assessments for exercise and sedentary behavior reinforcement (primary dependent variables) and activity and tolerance for exercise intensity were performed at baseline (week 0), post training (week 6), and post washout (week 10).

Results

The control group reduced (P = 0.022) relative reinforcing value of exercise, such that the 150 kcal group had a greater relative reinforcing value of exercise after the exercise treatment 150 kcal: 0.69 ± 0.07 to 0.74 ± 0.07; 300 kcal: 0.72 ± 0.07 to 0.63 ± 0.08, control: 0.72 ± 0.07 to 0.57 ± 0.08 mean ± SE. Increases in tolerance for exercise intensity discomfort were associated with increases in relative reinforcing value of exercise. Sedentary behavior reinforcement decreased in both exercise groups (150 kcal: 5.4 ± 4.3 to 1.8 ± 1.3; 300 kcal: 5.4 ± 4.3 to 3.1 ± 2.4, P<0.05), but remained unchanged in the control group (5.1 ± 4.0 to 6.1 ± 4.9, P>0.05). Sedentary activity decreased baseline to post-training in the 300 kcal group (546.5 ± 10.7 to 503.8 ± 11.8 minutes, P<0.01).

Conclusion

Small amounts of regular exercise may reduce the reinforcing value sedentary behavior. The process of incentive sensitization of exercise may include reducing the reinforcing value of competing sedentary activities. Developing tolerance to exercise discomfort of exercise may be critical to increasing exercise reinforcement.

Overexpression of Protein Kinase Inhibitor Alpha Reverses Rat Low Voluntary Running Behavior

A gene was sought that could reverse low voluntary running distances in a model of low voluntary wheel-running behavior. In order to confirm the low motivation to wheel-run in our model does not result from defects in reward valuation, we employed sucrose preference and conditioned place preference for voluntary wheel-access. We observed no differences between our model and wild-type rats regarding the aforementioned behavioral testing. Instead, low voluntary runners seemed to require less running to obtain similar rewards for low voluntary running levels compared to wild-type rats. Previous work in our lab identified protein kinase inhibitor alpha as being lower in low voluntary running than wild-type rats. Next, nucleus accumbens injections of an adenoviral-associated virus that overexpressed the protein kinase inhibitor alpha gene increased running distance in low voluntary running, but not wild-type rats. Endogenous mRNA levels for protein kinase inhibitor alpha, dopamine receptor D1, dopamine receptor D2, and Fos were all only lower in wild-type rats following overexpression compared to low voluntary runners, suggesting a potential molecular and behavioral resistance in wild-type rats. Utilizing a nucleus accumbens preparation, three intermediate early gene mRNAs increased in low voluntary running slices after dopamine receptor agonist SKF-38393 exposure, while wild-type had no response. In summary, the results suggest that protein kinase inhibitor alpha is a promising gene candidate to partially rescue physical activity in the polygenic model of low voluntary running. Importantly, there were divergent molecular responses to protein kinase inhibitor alpha overexpression in low voluntary runners compared to wild-type rats.

Running from fear: Exercise modulation of fear extinction

Extinction-based exposure therapy is the most common behavioral therapy for anxiety and trauma-related disorders, but fear tends to resurface even after successful extinction. Identification of novel strategies to enhance fear extinction and reduce fear relapse is of paramount importance to mental health. Exercise can enhance cognitive function, but it is not yet well understood whether exercise can be an effective augmentation strategy for fear extinction. In the current review, we present the current state of knowledge on the effects of exercise on fear extinction. Effects of exercise duration, explanations for conflicting results, and potential mechanisms, focusing on a hypothesized role for dopamine, are all discussed. We also provide new data suggesting that the timing in which acute exercise occurs relative to fear extinction, is a crucial variable in determining whether exercise can enhance fear extinction. Clinical implications and ideas to guide future research endeavors in this area are provided.

Auditory stimulation by exposure to melodic music increases dopamine and serotonin activities in rat forebrain areas linked to reward and motor control

Listening to melodic music is regarded as a non-pharmacological intervention that ameliorates various disease symptoms, likely by changing the activity of brain monoaminergic systems. Here, we investigated the effects of exposure to melodic music on the concentrations of dopamine (DA), serotonin (5-HT) and their respective metabolites in the caudate-putamen (CPu) and nucleus accumbens (NAcc), areas linked to reward and motor control. Male adult Wistar rats were randomly assigned to a control group or a group exposed to music. The music group was submitted to 8 music sessions [Mozart's sonata for two pianos (K. 488) at an average sound pressure of 65 dB]. The control rats were handled in the same way but were not exposed to music. Immediately after the last exposure or control session, the rats were euthanized, and their brains were quickly removed to analyze the concentrations of 5-HT, DA, 5-hydroxyindoleacetic acid (5-HIAA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the CPu and NAcc. Auditory stimuli affected the monoaminergic system in these two brain structures. In the CPu, auditory stimuli increased the concentrations of DA and 5-HIAA but did not change the DOPAC or 5-HT levels. In the NAcc, music markedly increased the DOPAC/DA ratio, suggesting an increase in DA turnover. Our data indicate that auditory stimuli, such as exposure to melodic music, increase DA levels and the release of 5-HT in the CPu as well as DA turnover in the NAcc, suggesting that the music had a direct impact on monoamine activity in these brain areas.

To Do or Not to Do: Dopamine, Affordability and the Economics of Opportunity

Five years ago, we introduced the thrift hypothesis of dopamine (DA), suggesting that the primary role of DA in adaptive behavior is regulating behavioral energy expenditure to match the prevailing economic conditions of the environment. Here we elaborate that hypothesis with several new ideas. First, we introduce the concept of affordability, suggesting that costs must necessarily be evaluated with respect to the availability of resources to the organism, which computes a value not only for the potential reward opportunity, but also the value of resources expended. Placing both costs and benefits within the context of the larger economy in which the animal is functioning requires consideration of the different timescales against which to compute resource availability, or average reward rate. Appropriate windows of computation for tracking resources requires corresponding neural substrates that operate on these different timescales. In discussing temporal patterns of DA signaling, we focus on a neglected form of DA plasticity and adaptation, changes in the physical substrate of the DA system itself, such as up- and down-regulation of receptors or release probability. We argue that changes in the DA substrate itself fundamentally alter its computational function, which we propose mediates adaptations to longer temporal horizons and economic conditions. In developing our hypothesis, we focus on DA D2 receptors (D2R), arguing that D2R implements a form of “cost control” in response to the environmental economy, serving as the “brain’s comptroller”. We propose that the balance between the direct and indirect pathway, regulated by relative expression of D1 and D2 DA receptors, implements affordability. Finally, as we review data, we discuss limitations in current approaches that impede fully investigating the proposed hypothesis and highlight alternative, more semi-naturalistic strategies more conducive to neuroeconomic investigations on the role of DA in adaptive behavior.

Predicting the ergogenic response to methylphenidate

PURPOSE

Methylphenidate (MPH) and other stimulants have been shown to enhance physical performance. However, stimulant research has almost exclusively been conducted in young, active persons with a normal BMI, and may not generalize to other groups. The purpose of this study was to determine whether the ergogenic response to MPH could be predicted by individual level characteristics.

METHODS

We investigated whether weekly minutes of moderate-to-vigorous physical activity (MVPA), age, and BMI could predict the ergogenic response to MPH. In a double-blind, cross-over design 29 subjects (14M, 15F, 29.7 ± 9.68 years, BMI: 26.1 ± 6.82, MVPA: 568.8 ± 705.6 min) ingested MPH or placebo before performing a handgrip task. Percent change in mean force between placebo and MPH conditions was used to evaluate the extent of the ergogenic response.

RESULTS

Mean force was significantly higher in MPH conditions [6.39% increase, T(25) = 3.09, p = 0.005 118.8 ± 37.96 (± SD) vs. 111.8 ± 34.99 Ns] but variable (coefficient of variation:163%). Using linear regression, we observed that min MVPA (T(25) = -2.15, β = -0.400, p = 0.044) and age [T(25) = -3.29, β = -0.598, p = 0.003] but not BMI [T(25) = 1.67, β = 0.320 p = 0.109] significantly predicted percent change in mean force in MPH conditions.

CONCLUSIONS

We report that lower levels of physical activity and younger age predict an improved ergogenic response to MPH and that this may be explained by differences in dopaminergic function. This study illustrates that the ergogenic response to MPH is partly dependent on individual differences such as habitual levels of physical activity and age.

Role of Inactivity in Chronic Diseases: Evolutionary Insight and Pathophysiological Mechanisms

This review proposes that physical inactivity could be considered a behavior selected by evolution for resting, and also selected to be reinforcing in life-threatening situations in which exercise would be dangerous. Underlying the notion are human twin studies and animal selective breeding studies, both of which provide indirect evidence for the existence of genes for physical inactivity. Approximately 86% of the 325 million in the United States (U.S.) population achieve less than the U.S. Government and World Health Organization guidelines for daily physical activity for health. Although underappreciated, physical inactivity is an actual contributing cause to at least 35 unhealthy conditions, including the majority of the 10 leading causes of death in the U.S. First, we introduce nine physical inactivity-related themes. Next, characteristics and models of physical inactivity are presented. Following next are individual examples of phenotypes, organ systems, and diseases that are impacted by physical inactivity, including behavior, central nervous system, cardiorespiratory fitness, metabolism, adipose tissue, skeletal muscle, bone, immunity, digestion, and cancer. Importantly, physical inactivity, itself, often plays an independent role as a direct cause of speeding the losses of cardiovascular and strength fitness, shortening of healthspan, and lowering of the age for the onset of the first chronic disease, which in turn decreases quality of life, increases health care costs, and accelerates mortality risk.

Maternal Western diet age-specifically alters female offspring voluntary physical activity and dopamine- and leptin-related gene expression

Prenatal overnutrition affects development into adulthood and influences risk of obesity. We assessed the transgenerational effect of maternal Western diet (WD) consumption on offspring physical activity. Voluntary wheel running was increased in juvenile (4-7 wk of age), but decreased in adult (16-19 wk of age), F₁ female WD offspring In contrast, no wheel-running differences in F₁ male offspring were observed. Increased wheel running in juvenile female WD offspring was associated with up-regulated dopamine receptor (DRD)-1 and -2 in the nucleus accumbens (NAc) and with down-regulated Lepr in the ventral tegmental area (VTA). Conversely, decreased wheel running by adult female WD offspring was associated with down-regulated DRD1 in the NAc and with up-regulated Lepr in the VTA. Body fat, leptin, and insulin were increased in male, but not in female, F₁ WD offspring. Recombinant virus (rAAV) leptin antagonism in the VTA decreased wheel running in standard diet but not in WD F₁ female offspring. Analysis of F₂ offspring found no differences in wheel running or adiposity in male or female offspring, suggesting that changes in the F₁ generation were related to in utero somatic reprogramming. Our findings indicate prenatal WD exposure leads to age-specific changes in voluntary physical activity in female offspring that are differentially influenced by VTA leptin antagonism.-Ruegsegger, G. N., Grigsby, K. B., Kelty, T. J., Zidon, T. M., Childs, T. E., Vieira-Potter, V. J., Klinkebiel, D. L., Matheny, M., Scarpace, P. J., Booth, F. W. Maternal Western diet age-specifically alters female offspring voluntary physical activity and dopamine- and leptin-related gene expression.