Exercise as a novel treatment for drug addiction: a neurobiological and stage-dependent hypothesis

Exercise in the context of substance use treatment: key issues and future directions

Substance Use Disorders (SUD) continue to be a significant public health concern. Exercise has been examined as an adjunctive approach to addiction treatment in an effort to improve mental health, physical health, and substance use outcomes. This review will present the existing evidence for the efficacy of exercise in the context of SUD treatment. In addition, we identify key factors, specific to this population, that may be contributing to treatment outcomes of exercise intervention studies. Lastly, we present a number of considerations for the development of more effective exercise interventions, in the future, with patients in SUD treatment.

Access to voluntary running wheel exercise: Prevention of anxiety-like behavior in chronically stressed rats, but potentiation of ethanol intake/preference

The current study tested the effect of voluntary running on future anxiety-like behavior, physiological response to stress, and ethanol intake/preference, while including a chronically stressed group and healthy group housed conspecifics. When given concurrently, voluntary running reduces ethanol intake, though it is unknown what effect voluntary running will have on anxiety-like behavior, corticosterone response to stress, and ethanol intake/preference when exercise is allowed only prior to ethanol access. Adolescent male Long Evans rats arrived in the lab at postnatal day (PND) 21. At PND 27, rats were either socially isolated (SI; n = 1/cage) or group housed (GH; n = 4/cage). Half of each group was allowed access to a running wheel for 30 min for 24 days from PND 35-66, and half of each group was not allowed access to a running wheel. After the housing/running procedure, we tested anxiety-like behavior using the elevated plus maze and stress responsivity by measuring corticosterone (CORT) levels before and after a swim stressor; then, rats were allowed intermittent access to ethanol in two-bottle choice design for four weeks. In accord with our hypothesis, running reduced anxiety-like behavior in SI runners compared to non-runners. Swim stress increased CORT levels but there was no difference in the response among groups. In regard to ethanol intake and preference, running (irrespective of housing group) increased intake at the 30 min time point and preference at the 24 h time point. Altogether, these data show that access to voluntary exercise was successful in reducing anxiety-like behavior, but withdrawal of exercise access appeared to enhance ethanol intake/preference. We suggest that these data reflect hedonic substitution.

Exercise during abstinence normalizes ultrastructural synaptic plasticity associated with nicotine-seeking following extended access self-administration

Nicotine-craving progressively increases, or incubates, over abstinence following extended access self-administration. While not yet examined for nicotine, the incubation of cocaine-seeking is accompanied by changes in synaptic plasticity in the nucleus accumbens. Here, we determined whether such changes also accompany enhanced nicotine-seeking following extended access self-administration and abstinence, and whether exercise, a potential intervention for nicotine addiction, may exert its efficacy by normalizing these changes. Given that in humans, tobacco/nicotine use begins during adolescence, we used an adolescent-onset model. Nicotine-seeking was assessed in male rats following extended access nicotine or saline self-administration (23-hr/day, 10 days) and 10 days of abstinence, conditions known to induce the incubation of nicotine-seeking, using a within-session extinction/cue-induced reinstatement procedure. A subset of rats had 2-hr/day access to a running wheel during abstinence. Ultrastructural alterations of synapses in the nucleus accumbens core and shell were examined using electron microscopy. Nicotine-seeking was elevated following extended access self-administration and abstinence (in sedentary group), and levels of seeking were associated with an increase in the density of asymmetric (excitatory) and symmetric (inhibitory) synapses onto dendrites in the core, as well as longer asymmetric synapses onto spines, a marker of synaptic potentiation, in both the core and shell. Exercise normalized each of these changes; however, in the shell, exercise and nicotine similarly increased the synapse length. Together, these findings indicate an association between nicotine-seeking and synaptic plasticity in the nucleus accumbens, particularly the core, and indicate that the efficacy of exercise to reduce nicotine-seeking may be mediated by reversing these adaptations.

Brief communication: β-cell function influences dopamine receptor availability

We aim to identify physiologic regulators of dopamine (DA) signaling in obesity but previously did not find a compelling relationship with insulin sensitivity measured by oral-minimal model (OMM) and DA subtype 2 and 3 receptor (D2/3R) binding potential (BPND). Reduced disposition index (DI), a β-cell function metric that can also be calculated by OMM, was shown to predict a negative reward behavior that occurs in states of lower endogenous DA. We hypothesized that reduced DI would occur with higher D2/3R BPND, reflecting lower endogenous DA. Participants completed PET scanning, with a displaceable radioligand to measure D2/3R BPND, and a 5-hour oral glucose tolerance test to measure DI by OMM. We studied 26 age-similar females without (n = 8) and with obesity (n = 18) (22 vs 39 kg/m2). Reduced DI predicted increased striatal D2/3R BPND independent of BMI. By accounting for β-cell function, we were able to determine that the state of insulin and glucose metabolism is pertinent to striatal D2/3R BPND in obesity. Clinical Trial Registration Number: NCT00802204.

Rewiring the Addicted Brain Through a Psychobiological Model of Physical Exercise

Drug addiction is a worldwide public health problem, resulting from multiple phenomena, including those both social and biological. Chronic use of psychoactive substances has been shown to induce structural and functional changes in the brain that impair cognitive control and favor compulsive seeking behavior. Physical exercise has been proven to improve brain function and cognition in both healthy and clinical populations. While some studies have demonstrated the potential benefits of physical exercise in treating and preventing addictive behaviors, few studies have investigated its cognitive and neurobiological contributions to drug-addicted brains. Here, we review studies in humans using cognitive behavioral responses and neuroimaging techniques, which reveal that exercise can be an effective auxiliary treatment for drug addictive disorders. Moreover, we describe the neurobiological mechanisms by which exercise-induced neuroplasticity in the prefrontal cortex improves executive functions and may decrease compulsive behaviors in individuals prone to substance use disorders. Finally, we propose an integrative cognitive-psychobiological model of exercise for use in future research in drug addiction and practical guidance in clinical settings.

Highlighting the Role of Cognitive and Brain Reserve in the Substance use Disorder Field

BACKGROUND

Cognitive reserve (CR) refers to the ability of an individual to cope with brain pathology remaining free of cognitive symptoms. This protective factor has been related to compensatory and more efficient brain mechanisms involved in resisting brain damage. For its part, Brain reserve (BR) refers to individual differences in the structural properties of the brain which could also make us more resilient to suffer from neurodegenerative and mental diseases.

OBJECTIVE

This review summarizes how this construct, mainly mediated by educational level, occupational attainment, physical and mental activity, as well as successful social relationships, has gained scientific attention in the last years with regard to diseases, such as neurodegenerative diseases, stroke or traumatic brain injury. Nevertheless, although CR has been studied in a large number of disorders, few researches have addressed the role of this concept in drug addiction.

METHODS

We provide a selective overview of recent literature about the role of CR and BR in preventing substance use onset. Likewise, we will also discuss how variables involved in CR (healthy leisure, social support or job-related activities, among others) could be trained and included as complementary activities of substance use disorder treatments.

RESULTS

Evidence about this topic suggests a preventive role of CR and BR on drug use onset and when drug addiction is established, these factors led to less severe addiction-related problems, as well as better treatment outcomes.

CONCLUSION

CR and BR are variables not taken yet into account in drug addiction. However, they could give us a valuable information about people at risk, as well as patient's prognosis.

Neuroprotective Effects of Forced Exercise and Bupropion on Chronic Methamphetamine-induced Cognitive Impairment via Modulation of cAMP Response Element-binding Protein/Brain-derived Neurotrophic Factor Signaling Pathway, Oxidative Stress, and Inflammatory Biomarkers in Rats

Background

Forced exercise can act as non-pharmacologic neuroprotective agent. In current study, we tried the involved molecular mechanisms of protective effects of forced exercise against methamphetamine induced neurodegeneration.

Materials and Methods

Forty adult male rats were divided to Group 1 and 2 which received normal saline and methamphetamine (10 mg/kg) respectively for 30 days. Groups 3, 4 and 5 were treated with methamphetamine for first 15 days and then were treated by forced exercise, bupropion (20 mg/kg/day) or combination of them for the following 15 days. Between 26^th and 30^th days, Morris Water Maze (MWM) was used to evaluate the cognition. On day 31, hippocampus was isolated from each rat and oxidative, antioxidant and inflammatory factors also the level of total and phosphorylated forms of cAMP response element-binding protein (CREB) and brain derived neurotrophic factor (BDNF) proteins were also evaluated.

Results

Chronic abuse of methamphetamine could decreases cognition and increase malondialdehyde (MDA), Tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β), while caused decreases in superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities all these changes was significant (P < 0.001) in compared to control group while treatment with bupropion, forced exercise and bupropion in combination with forced exercise could prevent all these malicious effects of methamphetamine (P < 0.001). Bupropion, forced exercise and bupropion in combination with forced exercise could activate CREB (both forms) and activates BDNF proteins' expression with P < 0.001 in methamphetamine treated rats.

Conclusions

P-CREB/BDNF signaling pathways might have critical role in forced exercise protective effects against methamphetamine induced neurodegeneration.

Anaerobic Exercise Training in the Therapy of Substance Use Disorders: A Systematic Review

Background: In the past 3 decades, there has been an increase in the number of studies assessing exercise as a form of treatment for substance use disorders (SUDs). While a variety of substance types and outcomes have been assessed, exercise intensities have never been systematically examined. Consequently, it remains unclear whether particular forms of exercise are better suited to the treatment of these populations. Anaerobic exercise has been shown to have positive effects in populations with psychiatric disorders, but its effectiveness in the treatment of SUDs has to date not been reviewed. Methods: The aim of this systematic review is to identify and evaluate studies which have employed either an acute or chronic anaerobic exercise component as a therapy modality for SUDs. The primary outcomes are abstinence, craving, withdrawal, consumption, quality of life, and the following psychological symptoms and disorders: depression, anxiety, stress, and mood. A secondary objective is to assess whether the type of training described in the study protocol can be reliably categorized as anaerobic training. Results: Twenty-six studies are included in this review. Twelve studies addressed nicotine dependence, one addressed alcohol dependence, and 13 addressed dependence on various illicit drugs. Thirteen studies reported the intensity at which participants actually exercised, but only one employed a test to determine whether training was carried out above the anaerobic threshold (AT). The risk of bias in the included studies was generally high. Results of the studies were mixed, with the most positive effects being found for abstinence in nicotine dependence. Conclusion: The evidence for the effects of anaerobic exercise in SUDs is weak, although a tendency toward positive effects on abstinence in nicotine dependent individuals was observable. The majority of studies do not report data on exercise intensity, making a categorization of anaerobic exercise impossible in all but one case. This means that the effects of this form of exercise cannot be determined, and therefore not evaluated or compared with other forms. In order to improve the quality of evidence for exercise in SUD treatment, clearly defined and objectively assessed evaluations of anaerobic and anaerobic exercise are necessary.

Inmates with Harmful Substance Use Increase Both Exercise and Nicotine Use Under Incarceration

Exercise is increasingly understood as an important resource for people who engage in harmful substance use, including those in prison. Little is known about how inmates adopt various health behaviors during incarceration, without interventions. This cross-sectional study analyzed self-reports from 1464 inmates in Norwegian prisons in 2013–2014, compared them according to harmful substance use pre-incarceration, and explored changes in exercise and nicotine use during incarceration. Results were presented in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Inmates with harmful substance use reported higher rates of smoking, smokeless tobacco, and physical inactivity pre-incarceration than inmates without harmful use. However, inmates with harmful use also exhibited more behavioral changes: they adopted exercise, ceased smoking, and adopted smokeless tobacco at higher rates during incarceration than the non-harmful group, to the extent that inmates with harmful use exercised during incarceration more. Exercise is being taken up by a significant proportion of inmates, and may in particular be a replacement behavior for substance use. However, unhealthy behaviors also begin or are maintained. If prisons were used as an arena to facilitate healthy behaviors, the public health benefits to a marginalized group such as substance-using inmates could be substantial.

Dopamine: Functions, Signaling, and Association with Neurological Diseases

The dopaminergic system plays important roles in neuromodulation, such as motor control, motivation, reward, cognitive function, maternal, and reproductive behaviors. Dopamine is a neurotransmitter, synthesized in both central nervous system and the periphery, that exerts its actions upon binding to G protein-coupled receptors. Dopamine receptors are widely expressed in the body and function in both the peripheral and the central nervous systems. Dopaminergic signaling pathways are crucial to the maintenance of physiological processes and an unbalanced activity may lead to dysfunctions that are related to neurodegenerative diseases. Unveiling the neurobiology and the molecular mechanisms that underlie these illnesses may contribute to the development of new therapies that could promote a better quality of life for patients worldwide. In this review, we summarize the aspects of dopamine as a catecholaminergic neurotransmitter and discuss dopamine signaling pathways elicited through dopamine receptor activation in normal brain function. Furthermore, we describe the potential involvement of these signaling pathways in evoking the onset and progression of some diseases in the nervous system, such as Parkinson's, Schizophrenia, Huntington's, Attention Deficit and Hyperactivity Disorder, and Addiction. A brief description of new dopaminergic drugs recently approved and under development treatments for these ailments is also provided.

Exploring Exercise- and Context-Induced Peptide Changes in Mice by Quantitative Mass Spectrometry

Recent research suggests that exercise may help facilitate abstinence from cocaine addiction, though the mechanisms are not well understood. In mice, wheel running accelerates the extinction of conditioned place preference (CPP) for cocaine, providing an animal model for evaluating potential neurological mechanisms. The objective of this study was to quantify dynamic changes in endogenous peptides in the amygdala and dentate gyrus of the hippocampus in mice exposed to a context paired with the effects of cocaine, and in response to exercise. Male C57BL/6J mice conditioned to cocaine were housed with or without running wheels for 30 days. Following a CPP test and final exposure to either a cocaine- or saline-associated context, peptides were measured in brain tissue extracts using label-free matrix-assisted laser desorption/ionization mass spectrometry (MS) and stable isotopic labeling with liquid chromatography and electrospray ionization MS. CPP in mice was significantly reduced with running, which correlated to decreased myelin basic protein derivatives in the dentate gyrus extracts, possibly reflecting increased unmyelinated granule neuron density. Exposure to a cocaine-paired context increased hemoglobin-derived peptides in runners and decreased an actin-derived peptide in sedentary animals. These results allowed us to characterize a novel set of biomarkers that are responsive to exercise in the hippocampus and in a cocaine-paired context in the amygdala.

Physical Activity Interventions to Decrease Substance Use in Youth: A Review of the Literature

BACKGROUND

Adolescent substance use, a major problem in the United States, has a significant negative effect on both short- and long-term mental and physical health. Physical activity (PA) may offer potentially effective strategies to combat substance use in youth. Like substance use, PA behaviors developed during adolescence persist into adulthood, so adolescence may be an ideal period in which to implement PA interventions to prevent substance abuse. However, there are no known systematic literature reviews of PA-based interventions that target substance use in adolescence.

OBJECTIVES

To review PA interventions for adolescents, including research designs, intervention characteristics, and measures of substance use.

METHODS

Five databases were searched for articles published in English peer-reviewed journals. Search terms were related to the adolescent population, substance use, and PA interventions.

RESULTS

17 articles fit inclusion criteria. The results suggest that PA interventions may decrease substance use in teens. A majority of the interventions were delivered in high schools. Substance use measures/outcomes included intention or willingness to use, cessation, and actual use. Alcohol use was measured most, followed by marijuana and tobacco use. Although most of the studies utilized group sessions to deliver interventions, decreased substance use was also associated with one-time, multi-health consultations. Conclusions/Importance: School-based interventions targeting multiple health behaviors may offer a particularly effective and efficient way to decrease substance use in adolescents.

Naltrexone: A History and Future Directions

Trying to kick drug addiction without medicines is said to be like relying on willpower to overcome diabetes or asthma. Enter naltrexone, which has been around since 1984 and reduces the cravings for drugs and alcohol by fine-tuning the brain's chemical reward system. Why has it recently increased in popularity? How does it compare to similar strategies? Has it made a difference? Our authors, who have long studied addiction and the brain, confront a drug and alcohol addiction problem that today kills more Americans each day than gun violence or car accidents.

Neurobiology of substance use in adolescents and potential therapeutic effects of exercise for prevention and treatment of substance use disorders

Substance use (e.g., alcohol, marijuana, opioids, cocaine., etc,) use often initiates during adolescence, a critical period of physiological and social development marked by an increase in risk-taking due, in part, to heightened motivation to obtain arousal from rewards. Substance use during adolescence has been associated with a greater risk of substance use disorders (SUD) in adulthood. Although use rates for most substances have remained relatively stable, the frequency of marijuana use and the perception that regular marijuana use is not harmful has increased in adolescents. Furthermore, the nonmedical use of opioids has increased, particularly in the South, Midwest, and rural low-income communities. Substance use in adolescence has been associated with adverse structural and functional brain changes and, may exacerbate the natural "imbalance" between frontal/regulatory and cortical-subcortical circuits, leading to further heightened impulsive and reward-driven behaviors. Exercise increases growth and brain-derived neurotrophic factors that stimulate endogenous dopaminergic systems that, in turn, enhance general plasticity, learning, and memory. Exercise may help to reinforce the "naïve" or underdeveloped connections between neurological reward and regulatory processes in adolescence from the "bottom up" and "offset" reward seeking from substances, while concomitantly improving cardiovascular health, as well as academic and social achievement. In this review, we provide an overview of the current state of substance use in adolescents and rationale for the utilization of exercise, particularly "assisted" exercise, which we have shown increases neural activity in cortical-subcortical regions and may modulate brain dopamine levels during adolescence, a unique window of heightened reward sensitivity and neural plasticity, for the prevention and adjunctive treatment of SUD.

Exercise Reduces Dopamine D1R and Increases D2R in Rats: Implications for Addiction

INTRODUCTION

Exercise has been shown to be effective for preventing and treating substance abuse in both clinical and preclinical studies. Less is known, however, regarding the underlying neurobiological mechanisms driving these changes in drug-seeking behavior. One possibility is that exercise may alter the mesolimbic dopamine pathway in such a way that makes drugs of abuse less salient and/or rewarding.

METHODS

To examine possible exercise-induced changes in dopamine signaling, male and female Lewis rats were split into exercise and sedentary groups at 8 wk of age. Exercise rats were run on a treadmill at 10 m·min, 5 d·wk, for 6 wk, whereas sedentary rats remained in their home cage. Rats were killed after the 6 wk of treatment, and their brains were used for in vitro autoradiography using [H]SCH 23,390, [H]Spiperone, and [H]WIN55,428 ligands to quantify dopamine type 1-like receptor (D1R)-like, dopamine type 2-like receptor (D2R)-like, and dopamine transporter binding, respectively.

RESULTS

Exercised rats had 18% and 21% lower D1R-like binding levels compared to sedentary rats within the olfactory tubercle and nucleus accumbens shell, respectively. In addition, male and female exercise rats showed greater D2R-like binding levels within the dorsomedial caudate putamen (30%), ventrolateral caudate putamen (24%), and ventromedial caudate putamen (27%), as well as the olfactory tubercle (19%). Greater D2R-like binding in the nucleus accumbens core (24%) and shell (25%) of exercised rats compared with sedentary rats approached significance. No effects were found for dopamine transporter binding.

CONCLUSIONS

These findings support the hypothesis that aerobic exercise results in changes in the mesolimbic pathway that could mediate exercise-induced attenuation of drug-seeking behavior.

Social Factors in Ethanol Sensitization

Behavioral sensitization is a neuroadaptive process characterized by an increase in a particular behavior after repeated exposure to drugs or other stimuli, such as stress. Sensitization can also be extended to neurochemical and neuroendocrine sensitization. Several factors can influence sensitization to the effects of ethanol. For instance, stress is an important component in addiction that can strengthen ethanol-induced behaviors. In animal models, stressful situations can be induced by alterations in social aspects of the animal's environment, such as maternal separation, social conflicts, and housing conditions. Social conflict models involve acute, chronic or intermittent interaction of an animal to a conspecific and can occur at any stage of life, including preweaning, adolescence or adulthood. These events can influence ethanol-induced behavioral sensitization in different ways, such as increases in locomotion, drug reward, and drug-taking behaviors. On the other hand, environmental enrichment can produce a protective phenotype against drug-related behaviors. In this chapter, we discuss findings regarding consequences of social stress and environmental enrichment on sensitization to ethanol.

Chronic forced exercise inhibits stress-induced reinstatement of cocaine conditioned place preference

Stress increases the likelihood of cocaine relapse in humans and animals, even following a prolonged extinction/abstinence period. Exercise has previously been shown to reduce stress and decrease the likelihood of drug dependence, while also reducing cravings in humans and inhibiting relapse behaviors due to other risk factors in rodents. The present study evaluated the efficacy of exercise to reduce stress-induced relapse to cocaine in a rodent model. Young adult female Sprague Dawley rats were tested for cocaine conditioned place preference (CPP), then split into sedentary or exercise (six weeks of one-hour daily treadmill running, five days per week) groups. Following cocaine CPP, rats were tested for extinction behavior, and then tested for stress-primed reinstatement (15 min immobilization) following the six-week intervention period. Exercise inhibited stress-induced reinstatement of cocaine CPP despite increasing serum corticosterone levels following 15 min of immobilization, suggesting that chronic aerobic exercise intervention may result in adaptations of stress pathways. These findings suggest that exercise may help prevent stress-induced drug relapse, adding to a growing body of evidence supporting the utility of exercise to combat substance abuse.

Health Benefits of Exercise

Overwhelming evidence exists that lifelong exercise is associated with a longer health span, delaying the onset of 40 chronic conditions/diseases. What is beginning to be learned is the molecular mechanisms by which exercise sustains and improves quality of life. The current review begins with two short considerations. The first short presentation concerns the effects of endurance exercise training on cardiovascular fitness, and how it relates to improved health outcomes. The second short section contemplates emerging molecular connections from endurance training to mental health. Finally, approximately half of the remaining review concentrates on the relationships between type 2 diabetes, mitochondria, and endurance training. It is now clear that physical training is complex biology, invoking polygenic interactions within cells, tissues/organs, systems, with remarkable cross talk occurring among the former list.

Aerobic exercise modulates anticipatory reward processing via the μ-opioid receptor system

Physical exercise modulates food reward and helps control body weight. The endogenous µ-opioid receptor (MOR) system is involved in rewarding aspects of both food and physical exercise, yet interaction between endogenous opioid release following exercise and anticipatory food reward remains unresolved. Here we tested whether exercise-induced opioid release correlates with increased anticipatory reward processing in humans. We scanned 24 healthy lean men after rest and after a 1 h session of aerobic exercise with positron emission tomography (PET) using MOR-selective radioligand [¹¹ C]carfentanil. After both PET scans, the subjects underwent a functional magnetic resonance imaging (fMRI) experiment where they viewed pictures of palatable versus nonpalatable foods to trigger anticipatory food reward responses. Exercise-induced changes in MOR binding in key regions of reward circuit (amygdala, thalamus, ventral and dorsal striatum, and orbitofrontal and cingulate cortices) were used to predict the changes in anticipatory reward responses in fMRI. Exercise-induced changes in MOR binding correlated negatively with the exercise-induced changes in neural anticipatory food reward responses in orbitofrontal and cingulate cortices, insula, ventral striatum, amygdala, and thalamus: higher exercise-induced opioid release predicted higher brain responses to palatable versus nonpalatable foods. We conclude that MOR activation following exercise may contribute to the considerable interindividual variation in food craving and consumption after exercise, which might promote compensatory eating and compromise weight control.

A Complier Average Causal Effect Analysis of the Stimulant Reduction Intervention using Dosed Exercise Study

Objective

Exercise is a promising treatment for substance use disorders, yet an intention-to-treat analysis of a large, multi-site study found no reduction in stimulant use for exercise versus health education. Exercise adherence was sub-optimal; therefore, secondary post-hoc complier average causal effects (CACE) analysis was conducted to determine the potential effectiveness of adequately dosed exercise.

Method

The STimulant use Reduction Intervention using Dosed Exercise study was a randomized controlled trial comparing a 12 kcal/kg/week (KKW) exercise dose versus a health education control conducted at nine residential substance use treatment settings across the U.S. that are affiliated with the National Drug Abuse Treatment Clinical Trials Network. Participants were sedentary but medically approved for exercise, used stimulants within 30 days prior to study entry, and received a DSM-IV stimulant abuse or dependence diagnosis within the past year. A CACE analysis adjusted to include only participants with a minimum threshold of adherence (at least 8.3 KKW) and using a negative-binomial hurdle model focused on 218 participants who were 36.2% female, mean age 39.4 years (SD = 11.1), and averaged 13.0 (SD = 9.2) stimulant use days in the 30 days before residential treatment. The outcome was days of stimulant use as assessed by the self-reported TimeLine Follow Back and urine drug screen results.

Results

The CACE-adjusted analysis found a significantly lower probability of relapse to stimulant use in the exercise group versus the health education group (41.0% vs. 55.7%, p < .01) and significantly lower days of stimulant use among those who relapsed (5.0 days vs. 9.9 days, p < .01).

Conclusions

The CACE adjustment revealed significant, positive effects for exercise. Further research is warranted to develop strategies for exercise adherence that can ensure achievement of an exercise dose sufficient to produce a significant treatment effect.

Physical Activity and the Development of Substance Use Disorders: Current Knowledge and Future Directions

Physical activity and exercise are positive health behaviors that have been shown to reduce the risk of physical and psychological diseases. There is a strong rationale that physical activity could be a protective factor against the development of substance use disorders (SUDs), which include some of the most common mental health conditions such as tobacco and alcohol use disorder. This review examined the epidemiological literature to describe the associations of physical activity and substance use across the lifespan. The findings indicated that physical activity is positively associated with current and future alcohol use but negatively associated with tobacco and other drug use, with the strongest support originating from adolescent and young adult samples. Considerably less data exist on physical activity and other drug use in later life. Limitations in previous studies, such as the indeterminate measurement of physical activity and absence of clinical substance use disorder endpoints, should be addressed in future investigations to provide clarity regarding the strength and directions of these relationships among different substances and populations.

Resistance exercise decreases heroin self-administration and alters gene expression in the nucleus accumbens of heroin-exposed rats

RATIONALE

Preclinical studies consistently report that aerobic exercise decreases drug self-administration and other forms of drug-seeking behavior; however, relatively few studies have examined other types of physical activity.

OBJECTIVES

The purpose of the present study was to examine the effects of resistance exercise (i.e., strength training) on heroin self-administration and mRNA expression of genes known to mediate opioid reinforcement and addictive behavior in the nucleus accumbens (NAc) of heroin-exposed rats.

METHODS

Female rats were obtained during late adolescence and divided into two groups. Resistance exercise rats were trained to climb a vertical ladder wearing a weighted vest; sedentary control rats were placed repeatedly on the ladder oriented horizontally on its side. All rats were implanted with intravenous catheters and trained to self-administer heroin on a fixed ratio (FR1) schedule of reinforcement. mRNA expression in the NAc core and shell was examined following behavioral testing.

RESULTS

Resistance exercise significantly decreased heroin self-administration, resulting in a downward shift in the dose-effect curve. Resistance exercise also reduced mRNA expression for mu opioid receptors and dopamine D1, D2, and D3 receptors in the NAc core. Resistance exercise increased mRNA expression of dopamine D5 receptors in the NAc shell and increased mRNA expression of brain-derived neurotrophic factor (exons I, IIB, IIC, IV, VI, IX) in the NAc core.

CONCLUSIONS

These data indicate that resistance exercise decreases the positive reinforcing effects of heroin and produces changes in opioid and dopamine systems in the NAc of heroin-exposed rats.

The impact of length of stay on recovery measures in faith-based addiction treatment

OBJECTIVE

To determine the impact of length of stay among homeless men in faith-based residential addictions recovery on physical activity, depression, self-esteem, and nicotine dependence.

DESIGN AND SAMPLE

A time series design was utilized to measure changes in the four quality measures at program entry and at 3, 6, and 9 months following admission. The sample consisted of 175 homeless residents enrolled in a faith-based residential recovery program.

MEASURES

Paired t tests were used to determine the change in average instrument response from admission to each follow-up period. Analysis of variance (ANOVA) and Tukey posthoc tests were used to assess for differences in length of stay between demographic variables.

RESULTS

Statistically significant improvements were noted in self-esteem and depressive symptomatology at 3 and 6 months following admission and in physical activity levels at 3 months following admission. Nicotine dependence scores declined at 3 and 6 months but were not statistically significant.

CONCLUSION

Time spent in this faith-based spiritual recovery program had a significant impact on depression, self-esteem, and physical activity. Recommendations for future study include conducting research to analyze the relationship between distinct program elements and quality indicators and comparing faith-based programs to other similar programs and to publicly funded secular recovery programs.

A Behavioral Economic Analysis of Marijuana and Other Drug Use Among Heavy Drinking Young Adults

Objective

Behavioral economic models predict that deficits in substance-free reward and future time orientation are associated with greater drug involvement, but this hypothesis has not been systematically investigated among young adult heavy drinkers. This study evaluated the association between drug use levels (heavy drinking (HD) only, HD + marijuana use, and HD + polysubstance use) and substance-free activity engagement, future orientation, and reward deprivation (comprised of reward experience and environmental suppressors of reward) among heavy drinkers.

Method

Participants were 358 college students who reported two or more past-month heavy drinking episodes (5/4 or more drinks in one occasion for a man/woman). The sample was 60% women, 79% Caucasian, and the average age was 18.76 (SD = 1.07) years. Participants completed measures of alcohol and drug use, weekly time allocation to various activities, future time orientation, and reward deprivation.

Results

Overall, any drug use was associated with less time spent engaged in academics and exercise, and lower future time orientation compared to HD only. Any drug use was associated with reward deprivation and HD + polysubstance use was associated with lower reward experience and environmental suppressors.

Conclusion

Drug use among heavy drinkers is associated with lower academic engagement and exercise, future orientation, and reward deprivation. These results provide support for behavioral economic models of drug abuse and suggest that prevention approaches should attempt to increase future orientation and availability of drug-free reward.

Development and Initial Validation of a Rock Climbing Craving Questionnaire (RCCQ)

Conceptual similarities have been identified between experiences of extreme sports athletes and those with drug and behavioral addictions. Evidence suggests rock climbers experience craving and other withdrawal-like states when abstinent from their sport. However, no studies have attempted to quantitatively measure the craving experienced by participants of any extreme sports. Such a measure could allow a greater understanding of the craving experienced by extreme sports athletes and a comparison of these across sports (e.g., surfing) and activities (e.g., drug-use). Therefore, using validated craving measures as a template, the aim of the two studies outlined here was to design and preliminarily validate a subjective multidimensional inventory that could be used to measure craving in the sports of rock-climbing and mountaineering (“RCCQ”). The aim of the first study was to investigate the factor structure of a preliminary measure of craving. Climbers (n = 407) completed the RCCQ. A 3-factor model explained 53.65% of the total variance in item scores. All three factors comprised five items each, which were conceptually labeled as “urge to climb” “negative reinforcement” and “positive reinforcement.” The aim of the second study was to validate the 15-item 3-factor RCCQ resulting from Study 1 using confirmatory factor analysis (CFA). Climbers (n = 254) completed the questionnaire under a climbing-related cue condition or a cue-neutral condition. CFA revealed a good model fit and that all individual parameter estimates were significant and standard errors were within reasonable limits once item 13 was removed from Factor 1. Study 1 supports the multi-dimensional nature of rock climbing craving and shows parallels with substance-related craving in reflecting intention and positive (desire) and negative (withdrawal) reinforcement. Study 2 confirms this factor structure and gives initial validation to the measure with evidence that these factors are sensitive to cue exposure. Given the preliminary nature of the data, any practical implications are tentative. However, if as shown here, craving for climbing (and potentially other extreme sports) is similar to that experienced by drug-users and addicts, there is the potential that climbing and other extreme sports could be used as a replacement therapy for drug users.

A Role for Exercise in Attenuating Unhealthy Food Consumption in Response to Stress

It is well established that both acute and chronic stress can be detrimental to health and wellbeing by directly increasing the risk of several chronic diseases and related health problems. In addition, stress may contribute to ill-health indirectly via its downstream effects on individuals’ health-related behaviour, such as promoting the intake of unhealthy palatable foods high in fat and sugar content. This paper reviews (a) the research literature on stress-models; (b) recent research investigating stress-induced eating and (c) the potential physiological and psychological pathways contributing to stress-induced eating. Particular attention is given to (d) the role of physical exercise in attenuating acute stress, with exploration of potential mechanisms through which exercise may reduce unhealthy food and drink consumption subsequent to stressor exposure. Finally, exercise motivation is discussed as an important psychological influence over the capacity for physical exercise to attenuate unhealthy food and drink consumption after exposure to stressors. This paper aims to provide a better understanding of how physical exercise might alleviate stress-induced unhealthy food choices.

The neurobiological mechanisms of physical exercise in methamphetamine addiction

Methamphetamine (METH) is the primary drug within amphetamine-type stimulants which are the second most abused group of drugs worldwide. There is no pharmacological treatment addressed specifically to METH addiction, and behavioral therapy is shadowed by poor long-term recovery and relapse. Therefore, novel approaches to manage METH addiction are an urgent need. This review aims to describe the current state of physical exercise use on methamphetamine addiction management. The following searching terms in PubMed were used: ("physical exercise" OR "exercise") AND "methamphetamine." Relevant references from key publications and gray literature were also reviewed to identify additional citations for inclusion. Original investigation regarding physical exercise and methamphetamine addiction (clinical data) or neurobiological mechanisms of physical exercise in animal models of methamphetamine administration (preclinical data) was included. Overall, METH users demonstrated improvements, including better fitness and emotional measures, lower relapse rates, and sustained abstinence when compared to nonexercised individuals. The neurobiological mechanisms of physical exercise in METH users seem to reflect an interplay of several agents, including neurochemicals, oxidative stress, neurogenesis, gliogenesis, and blood-brain barrier as disclosed by preclinical data. Exercise-based interventions alone or as a conjoint therapy may be a useful tool for managing METH addiction.

Repeated Morphine Produces Sensitization to Reward and Tolerance to Antiallodynia in Male and Female Rats with Chemotherapy-Induced Neuropathy

Paclitaxel is a cancer chemotherapy drug with adverse effects that include chemotherapy-induced neuropathic pain (CINP) as well as depression of behavior and mood. In the clinical setting, opioids are often used concurrently with or after chemotherapy to treat pain related to the cancer or CINP, but repeated opioid exposure can also increase the risk of opioid abuse. In this study, male and female Sprague-Dawley rats were used to test the hypothesis that repeated 3.2-mg/kg doses of morphine would induce tolerance to its antinociceptive effects in a mechanical sensitivity assay and increased expression of its abuse-related rewarding effects in an assay of intracranial self-stimulation (ICSS). Three weeks after four injections of vehicle or 2.0 mg/kg of paclitaxel, the initial morphine dose-effect curves were determined in both assays. Subsequently, rats were treated with 3.2 mg/kg per day morphine for 6 days. On the final day of testing, morphine dose-effect curves were redetermined in both assays. On initial exposure, morphine produced dose-dependent antiallodynia in the assay of mechanical sensitivity, but it produced little or no rewarding effects in the assay of ICSS. After 6 days of repeated treatment, morphine antiallodynia decreased, and morphine reward increased. Females exhibited greater morphine reward on initial exposure than males, but repeated morphine eliminated this sex difference. These results suggest that repeated morphine may produce tolerance to therapeutically beneficial analgesic effects of morphine but increased sensitivity to abuse-related rewarding effects of morphine in subjects treated with paclitaxel.

Physical activity and the prevention, reduction, and treatment of alcohol and/or substance use across the lifespan (The PHASE review): protocol for a systematic review

BACKGROUND

Alcohol and substance use results in significant human and economic cost globally and is associated with economic costs of £21 billion and £15billion within the UK, respectively, and trends for use are not improving. Pharmacological interventions are well researched, but relapse rates across interventions for substance and alcohol use disorders are as high as 60-90%. Physical activity may offer an alternative or adjunct approach to reducing rates of alcohol and substance use that is associated with few adverse side effects, is easily accessible, and is potentially cost-effective. Through psychological, behavioural, and physiological mechanisms, physical activity may offer benefits in the prevention, reduction, and treatment of alcohol and substance use across the lifespan. Whilst physical activity is widely advocated as offering benefit, no systematic review exists of physical activity (in all forms) and its effects on all levels of alcohol and substance use across all ages to help inform policymakers, service providers, and commissioners.

METHODS

The objectives of this mixed methods systematic review are to describe and evaluate the quantitative and qualitative research obtained by a diverse search strategy on the impact of physical activity and its potential to: 1. Reduce the risk of progression to alcohol and/or substance use (PREVENTION) 2. Support individuals to reduce alcohol and/or substance use for harm reduction (REDUCTION), and 3. Promote abstinence and relapse prevention during and after treatment for an alcohol and/or substance use disorder (TREATMENT). With the input of key stakeholders, we aim to assess how what we know can be translated into policy and practice. Quantitative, qualitative, service evaluations, and economic analyses will be brought together in a final narrative synthesis that will describe the potential benefits of physical activity for whom, in what conditions, and in what form.

DISCUSSION

This review will provide details of what is known about physical activity and the prevention, reduction, and treatment of alcohol and/or substance use. The synthesised findings will be disseminated to policymakers, service providers, and commissioners in the UK.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO number: CRD42017079322 .

PSYCHOLOGICAL AND SOCIODEMOGRAPHIC CHARACTERISTICS AND DEVELOPMENT OF PHYSICAL EXERCISE DEPENDENCE

ABSTRACT Introduction: Excessive physical exercise combined with certain psychic and sociodemographic factors can lead to dependence. Objective: To examine which factors lead to the emergence of exercise dependence. Methods: Sample consisted of 103 men (mean age 27.3 years, SD 6.127) who performed exercises at gyms at least three times a week in the last year or more in Novi Pazar, Sjenica, Raska and Tutin, Serbia. Participants completed questionnaires and took appropriate tests. Results: Our results showed that there is no association between exercise dependence and financial status, number of siblings, level of education, family stability, health, and medication use among the interviewees. However, it was found that the degree of exercise dependence is associated with marital status and problems with the law. Regression analysis showed that body dysmorphia, body mass index and aggressiveness are better predictors of exercise dependence. Conclusion: People whose self-perception is dismorphic have lower self-esteem, and exercise in gyms to improve their physical appearance. If we consider other characteristics, such as unfavorable BMI, problems with the lаw and being single, it is hardly surprising these individuals cross the line between healthy exercise and exercise dependence. An important finding is that aggressiveness and exercise dependence are related to problems with the law due to aggression, and body dysmorphia. Level of Evidence; Diagnostic studies - Investigating a diagnostic test.

Exercise and epigenetic inheritance of disease risk

Epigenetics is the study of gene expression changes that occur in the absence of altered genotype. Current evidence indicates a role for environmentally induced alterations to epigenetic modifications leading to health and disease changes across multiple generations. This phenomenon is called intergenerational or transgenerational epigenetic inheritance of health or disease. Environmental insults, in the form of toxins, plastics and particular dietary interventions, perturb the epigenetic landscape and influence the health of F1 through to F4 generations in rodents. There is, however, the possibility that healthy lifestyles and environmental factors, such as exercise training, could lead to favourable, heritable epigenetic modifications that augment transcriptional programmes protective of disease, including metabolic dysfunction, heart disease and cancer. The health benefits conferred by regular physical exercise training are unquestionable, yet many of the molecular changes may have heritable health implications for future generations. Similar to other environmental factors, exercise modulates the epigenome of somatic cells and researchers are beginning to study exercise epigenetics in germ cells. The germ cell epigenetic modifications affected by exercise offer a molecular mechanism for the inheritance of health and disease risk. The aims of this review are to: (i) provide an update on the expanding field of exercise epigenetics; (ii) offer an overview of data on intergenerational/transgenerational epigenetic inheritance of disease by environmental insults; (iii) to discuss the potential of exercise-induced intergenerational inheritance of health and disease risk; and finally, outline potential mechanisms and avenues for future work on epigenetic inheritance through exercise.

Yoga as an Adjunctive Intervention to Medication-Assisted Treatment with Buprenorphine+Naloxone

Objective

According to the CDC, 2.6 million people in the United States have an opioid use disorder and drug overdose is the leading cause of accidental death. Opioids are involved in 63% of overdose deaths. It is imperative that we identify evidence based treatments to stem the tide of this epidemic. This pilot study serves to explore the feasibility and effectiveness of Yoga as an adjunctive intervention for individuals with opioid use disorder in active medication-assisted treatment (MAT).

Methods

Participants (N=26) were recruited from a buprenorphine/naloxone MAT program to participate in this study. 13 participants engaged in a 12 week adjunctive yoga intervention while remaining in treatment as usual (TAU) MAT. 13 matched controls were recruited and remained in TAU MAT. Both groups were evaluated at baseline, 45 days and 90 days for changes in craving for opioids, treatment retention, relapse rates, sleep, and symptoms of anxiety and perceived stress.

Results

A two-way treatment by time analysis of variance was performed using a mixed effects model. The treatment by follow-up time interaction effect was significant for perceived stress (p=0.026) indicating that the yoga intervention had a larger effect than TAU (MAT). Changes in perceived stress decreased significantly over time in both the yoga intervention group and the TAU MAT matched control group.

Conclusion

This pilot study indicated strong evidence for Yoga being an effective adjunctive treatment to MAT TAU in reducing perceived stress. Further research with a larger population is needed to determine impact on other mental health symptoms and relapse and retention rates.

Drug, nicotine, and alcohol use among exercisers: Does substance addiction co-occur with exercise addiction?

Background

Scholastic works suggest that those at risk for exercise addiction are also often addicted to illicit drugs, nicotine, and/or alcohol, but empirical evidence is lacking.

Aims

The aim of the present work was to examine the co-occurrence of illicit drug, nicotine, and alcohol use frequency (prevalence of users) and severity (level of problem in users) among exercisers classified at three levels of risk for exercise addiction: (i) asymptomatic, (ii) symptomatic, and (iii) at-risk.

Methods

A sample of 538 regular exercisers were surveyed via the Qualtrics research platform. They completed the (i) Drug Use Disorder Identification Test, (ii) Fagerström Test for Nicotine Dependence, (iii) Alcohol Use Disorder Identification Test, and (iv) Exercise Addition Inventory.

Results

A large proportion (n = 59; 10.97%) of the sample was found to be at risk for exercise addiction. The proportion of drug and alcohol users among these participants did not differ from the rest of the sample. However, the incidence of nicotine consumption was lowest among them. The severity of problematic substance use did not differ across the groups.

Conclusions

These findings suggest that substance addiction and the risk for exercise addiction are unrelated. In fact, those at risk for exercise addiction exhibited the healthiest profile related to the prevalence of smoking.

•

Exercise addiction is unrelated to greater prevalence of alcohol or substance use.

•

Problematic alcohol or substance use is not a characteristic of exercise addiction.

•

The risk for exercise addiction is related to a lower prevalence of nicotine use.

Exercise as a Prevention for Substance Use Disorder: A Review of Sex Differences and Neurobiological Mechanisms

PURPOSE OF REVIEW

This report provides an update on clinical and preclinical findings for the efficacy of exercise to prevent substance use disorder with a focus on recent evidence for sex differences and neurobiological mechanisms.

RECENT FINDINGS

Exercise/physical activity is associated with decreased drug use in humans. Preclinical results further indicate that exercise decreases vulnerability to drug use and the development of features of substance use disorder, and suggest that females have an enhanced sensitivity to its reward-substitution effects. However, certain exercise conditions may sensitize the reward pathway and enhance vulnerability suggesting that parallel observations in humans (e.g., increased prescription opioid misuse and heroin use in high-school athletes) may be biologically-based.

SUMMARY

Exercise is a promising prevention strategy for substance use disorder. Further work is needed to establish its efficacy as a sex-specific strategy using larger samples, and to understand the exercise conditions that induce beneficial versus risk-enhancing effects.

Exercise as a Sex-Specific Treatment for Substance Use Disorder

PURPOSE OF REVIEW

Exercise is a promising treatment for substance use disorder that may reduce withdrawal symptoms and prevent relapse. In this review, we discuss recent evidence from clinical and preclinical studies for its efficacy, from a behavioral to a molecular level, in order to understand the exercise conditions that lead to beneficial effects. We also highlight the few recent findings of sex-specific differences.

RECENT FINDINGS

Clinical and preclinical findings show that exercise decreases withdrawal symptoms, including craving, in both males and females. Evidence from clinical studies support the efficacy of exercise to prevent relapse to smoking, although further research is needed to examine sex differences, establish long-term efficacy, and to determine if effects extend to other substance use disorders. Preclinical findings also support the potential utility of exercise to prevent relapse with evidence suggesting that its efficacy is enhanced in males, and mediated by blocking drug-induced adaptations that occur during early abstinence.

SUMMARY

Sex differences and timing of exercise availability during abstinence should be considered in future studies examining exercise as an intervention for relapse. A better understanding of the neurobiological mechanisms underlying the efficacy of exercise to reduce withdrawal symptoms and prevent relapse is needed to guide its development as a sex-specific treatment.

Exercise or saccharin during abstinence block estrus-induced increases in nicotine-seeking

Recent evidence suggests that adolescent and young adult females may be particularly responsive to nicotine use interventions that include exercise or environmental enrichment. This possibility was addressed in the current study by comparing the efficacy of exercise versus non-exercise environmental enrichment (saccharin) during abstinence at reducing subsequent nicotine-seeking/relapse vulnerability in an adolescent-onset rat model. The efficacy of each intervention was examined as a function of estrous cycle phase given findings indicating that hormonal status influences relapse vulnerability and treatment outcome in females. Once adolescent female rats acquired nicotine self-administration, they were given 23-h/day access to nicotine (0.01mg/kg/infusion) for 10days. Following the last self-administration session, rats began a 10-day forced abstinence period with 2-h/day access to an unlocked wheel (exercise, n=15), a bottle containing a saccharin-sweetened solution (0.25%; saccharin, n=19), or without access to a wheel or saccharin (control, n=20). Nicotine-seeking, as assessed under an extinction/cued-induced reinstatement procedure, was examined on day 11 of abstinence. Levels of nicotine-seeking were highest in females tested during estrus as compared to females tested during non-estrus phases. Exercise or saccharin during abstinence reduced nicotine-seeking in females tested during estrus, but neither affected the low levels of nicotine-seeking observed in females tested during non-estrus phases, presumably due to a floor effect. These results demonstrate that exercise or saccharin during abstinence decrease nicotine-seeking, and suggest that either would be effective as an early intervention for nicotine use and addiction in females.

Platelet Endothelial Cell Adhesion Molecule-1 and Oligodendrogenesis: Significance in Alcohol Use Disorders

Alcoholism is a chronic relapsing disorder with few therapeutic strategies that address the core pathophysiology. Brain tissue loss and oxidative damage are key components of alcoholism, such that reversal of these phenomena may help break the addictive cycle in alcohol use disorder (AUD). The current review focuses on platelet endothelial cell adhesion molecule 1 (PECAM-1), a key modulator of the cerebral endothelial integrity and neuroinflammation, and a targetable transmembrane protein whose interaction within AUD has not been well explored. The current review will elaborate on the function of PECAM-1 in physiology and pathology and infer its contribution in AUD neuropathology. Recent research reveals that oligodendrocytes, whose primary function is myelination of neurons in the brain, are a key component in new learning and adaptation to environmental challenges. The current review briefly introduces the role of oligodendrocytes in healthy physiology and neuropathology. Importantly, we will highlight the recent evidence of dysregulation of oligodendrocytes in the context of AUD and then discuss their potential interaction with PECAM-1 on the cerebral endothelium.

Effects of social reorganization on dopamine D2/D3 receptor availability and cocaine self-administration in male cynomolgus monkeys

RATIONALE

Studies have demonstrated that brain dopamine D2/D3 receptors (D2/D3R) and the reinforcing effects of cocaine can be influenced by a monkey's position in the social dominance hierarchy.

OBJECTIVE

In this study, we manipulated the social ranks of monkeys by reorganizing social groups and assessed effects on D2/D3R availability and cocaine self-administration.

METHODS

Male cynomolgus monkeys (N = 12) had been trained to self-administer cocaine under a concurrent cocaine-food reinforcement schedule. Previously, PET measures of D2/D3R availability in the caudate nucleus and putamen had been obtained with [18F]fluoroclebopride during cocaine abstinence, while monkeys lived in stable social groups of four monkeys/pen. For this study, monkeys were reorganized into groups that consisted of (1) four previously dominant, (2) four previously subordinate, and (3) a mix of previously dominant and subordinate monkeys. After 3 months, D2/D3R availability was redetermined and cocaine self-administration was reexamined.

RESULTS

D2/D3R availability significantly increased after reorganization in monkeys who were formerly subordinate, with the greatest increases observed in those that became dominant. No consistent changes in D2/D3R availability were observed in formerly dominant monkeys. Cocaine self-administration did not vary according to rank after reorganization of social groups. However, when compared to their previous cocaine self-administration data, the potency of cocaine as a reinforcer decreased in 9 of 11 monkeys.

CONCLUSIONS

These results indicate that changing the social conditions can alter D2/D3R availability in subordinate monkeys in a manner suggestive of environmental enrichment. In most monkeys, social reorganization shifted the cocaine dose-response curve to the right, also consistent with environmental enrichment.

Adolescent binge ethanol exposure alters specific forebrain cholinergic cell populations and leads to selective functional deficits in the prefrontal cortex

Adolescence has been identified as a vulnerable developmental time period during which exposure to drugs can have long-lasting, detrimental effects. Although adolescent binge-like ethanol (EtOH) exposure leads to a significant reduction in forebrain cholinergic neurons, EtOH's functional effect on acetylcholine (ACh) release during behavior has yet to be examined. Using an adolescent intermittent ethanol exposure model (AIE), rats were exposed to binge-like levels of EtOH from postnatal days (PD) 25 to 55. Three weeks following the final EtOH exposure, cholinergic functioning was assessed during a spontaneous alternation protocol. During maze testing, ACh levels increased in both the hippocampus and prefrontal cortex. However, selectively in the prefrontal cortex, AIE rats displayed reduced levels of behaviorally relevant ACh efflux. We found no treatment differences in spatial exploration, spatial learning, spatial reversal, or novel object recognition. In contrast, AIE rats were impaired during the first attentional set shift on an operant set-shifting task, indicative of an EtOH-mediated deficit in cognitive flexibility. A unique pattern of cholinergic cell loss was observed in the basal forebrain following AIE: Within the medial septum/diagonal band there was a selective loss (30%) of choline acetyltransferase (ChAT)-positive neurons that were nestin negative (ChAT+/nestin-); whereas in the Nucleus basalis of Meynert (NbM) there was a selective reduction (50%) in ChAT+/nestin+. These results indicate that early adolescent binge EtOH exposure leads to a long-lasting frontocortical functional cholinergic deficit, driven by a loss of ChAT+/nestin+ neurons in the NbM, which was associated with impaired cognitive flexibility during adulthood.

Sex determines effect of physical activity on diet preference: Association of striatal opioids and gut microbiota composition

Previous studies suggest an interaction between the level of physical activity and diet preference. However, this relationship has not been well characterized for sex differences that may exist. The present study examined the influence of sex on diet preference in male and female Wistar rats that were housed under either sedentary (no wheel access) (SED) or voluntary wheel running access (RUN) conditions. Following a 1 week acclimation period to these conditions, standard chow was replaced with concurrent ad libitum access to a choice of 3 pelleted diets (high-fat, high-sucrose, and high-corn starch) in the home cage. SED and RUN conditions remained throughout the next 4 week diet preference assessment period. Body weight, running distance, and intake of each diet were measured daily. At the conclusion of the 4 week diet preference test, animals were sacrificed and brains were collected for mRNA analysis. Fecal samples were also collected before and after the 4 week diet preference phase to characterize microbiota composition. Results indicate sex dependent interactions between physical activity and both behavioral and physiological measures. Females in both RUN and SED conditions preferred the high-fat diet, consuming significantly more high-fat diet than either of the other two diets. While male SED rats also preferred the high-fat diet, male RUN rats consumed significantly less high-fat diet than the other groups, instead preferring all three diets equally. There was also a sex dependent influence of physical activity on both reward related opioid mRNA expression in the ventral striatum and the characterization of gut microbiota. The significant sex differences in response to physical activity observed through both behavioral and physiological measures suggest potential motivational or metabolic difference between males and females. The findings highlight the necessity for further exploration between male and female response to physical activity and feeding behavior.

Modeling the development of drug addiction in male and female animals

An increasing emphasis has been placed on the development and use of animal models of addiction that capture defining features of human drug addiction, including escalation/binge drug use, enhanced motivation for the drug, preference for the drug over other reward options, use despite negative consequences, and enhanced drug-seeking/relapse vulnerability. The need to examine behavior in both males and females has also become apparent given evidence demonstrating that the addiction process occurs differently in males and females. This review discusses the procedures that are used to model features of addiction in animals, as well as factors that influence their development. Individual differences are also discussed, with a particular focus on sex differences. While no one procedure consistently produces all characteristics, different models have been developed to focus on certain characteristics. A history of escalating/binge patterns of use appears to be critical for producing other features characteristic of addiction, including an enhanced motivation for the drug, enhanced drug seeking, and use despite negative consequences. These characteristics tend to emerge over abstinence, and appear to increase rather than decrease in magnitude over time. In females, these characteristics develop sooner during abstinence and/or following less drug exposure as compared to males, and for psychostimulant addiction, may require estradiol. Although preference for the drug over other reward options has been demonstrated in non-human primates, it has been more difficult to establish in rats. Future research is needed to define the parameters that optimally induce each of these features of addiction in the majority of animals. Such models are essential for advancing our understanding of human drug addiction and its treatment in men and women.

Treadmill exercise delays the onset of non-motor behaviors and striatal pathology in the CAG140 knock-in mouse model of Huntington's disease

Depression, cognitive impairments, and other neuropsychiatric disturbances are common during the prodromal phase of Huntington's disease (HD) well before the onset of classical motor symptoms of this degenerative disorder. The purpose of this study was to examine the potential impact of physical activity in the form of exercise on a motorized treadmill on non-motor behavioral features including depression-like behavior and cognition in the CAG₁₄₀ knock-in (KI) mouse model of HD. The CAG₁₄₀ KI mouse model has a long lifespan compared to other HD rodent models with HD motor deficits emerging after 12months of age and thus provides the opportunity to investigate early life interventions such as exercise on disease progression. Motorized treadmill running was initiated at 4weeks of age (1h per session, 3 times per week) and continued for 6months. Non-motor behaviors were assessed up to 6months of age and included analysis of depression-like behavior (using the tail-suspension and forced-swim tests) and cognition (using the T-maze and object recognition tests). At both 4 and 6months of age, CAG₁₄₀ KI mice displayed significant depression-like behavior in the forced swim and tail suspension tests and cognitive impairment by deficits in reversal relearning in the T-maze test. These deficits were not evident in mice engaged in treadmill running. In addition, exercise restored striatal dopamine D2 receptor expression and dopamine neurotransmitter levels both reduced in sedentary HD mice. Finally, we examined the pattern of striatal expression of mutant huntingtin (mHTT) protein and showed that the number and intensity of immunohistochemical staining patterns of intranuclear aggregates were significantly reduced with exercise. Altogether these findings begin to address the potential impact of lifestyle and early intervention such as exercise on modifying HD progression.

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.

Social Status in Monkeys: Effects of Social Confrontation on Brain Function and Cocaine Self-Administration

Individual differences in response to social stress and environmental enrichment may contribute to variability in response to behavioral and pharmacological treatments for drug addiction. In monkeys, social status influences the reinforcing effects of cocaine and the effects of some drugs on cocaine self-administration. In this study, we used male cynomolgus macaques (n=15) living in established social groups to examine the effects of social confrontation on the reinforcing effects of cocaine using a food-drug choice procedure. On the test day, a dominant or subordinate monkey was removed from his homecage and placed into another social pen; 30 min later he was studied in a cocaine-food choice paradigm. For the group, following social confrontation, sensitivity to cocaine reinforcement was significantly greater in subordinate monkeys compared with dominant animals. Examining individual-subject data revealed that for the majority of monkeys (9/15), serving as an intruder in another social group affected cocaine self-administration and these effects were dependent on the social rank of the monkey. For subordinate monkeys, sensitivity to the reinforcing effects of cocaine increased while sensitivity decreased in dominant monkeys. To investigate potential mechanisms mediating these effects, brain glucose metabolism was studied in a subset of monkeys (n=8) using [18F]fluorodeoxyglucose ([18F]FDG) with positron emission tomography. Dominant and subordinate monkeys displayed distinctly different patterns of brain glucose metabolism in their homecage, including areas associated with vigilance and stress/anxiety, respectively, and during social confrontation. These data demonstrate that, depending on an individual's social status, the same social experience can have divergent effects on brain function and cocaine self-administration. These phenotypic differences in response to social conditions support a personalized treatment approach to cocaine addiction.

A pilot randomized trial of exercise as adjunct therapy in a heroin-assisted treatment setting

BACKGROUND

Although the potential of exercise as an adjunct treatment for substance dependence is persuasive in theory, few controlled trials have assessed its effectiveness. Existing research has also largely focused on individuals aiming towards, or having already achieved, abstinence. This study employed a randomized design in a pilot trial to assess the feasibility, acceptance, and effects of an exercise intervention for individuals receiving outpatient heroin-assisted treatment.

METHOD

50 individuals receiving heroin-assisted treatment at a clinic in Switzerland were invited to take part in the trial. Participants were randomized to 12weeks of exercise twice per week, or a corresponding duration of non-exercise group activities in a comparison condition. Data on attendance, compliance, and numerous psychological and physiological parameters were gathered.

RESULTS

24 individuals were willing to take part in the study. 92.3% of the exercise condition (n=13) were compliant or semi-compliant with the protocol; by contrast, only 54.6% of participants in the comparison condition (n=11) were compliant or semi-compliant (χ₂=7.049; p=0.029). Participants in the exercise condition significantly increased the number of minutes spent exercising at a high intensity level (F(2,44)=3.794; p=0.046; η²=0.159). No other significant interaction effects were observed.

CONCLUSIONS

An exercise intervention is a feasible and accepted supplementary therapy to heroin-assisted treatment. Participation rates were high, particularly given the outpatient setting. No evidence regarding the potential mechanisms of exercise as a therapy modality could be identified. Patients in heroin-assisted treatment may require a longer-term exercise programme, specifically targeting particular health parameters, before measurable improvements can be observed.