Gene expression of catecholamine biosynthetic enzymes following exercise: modulation by age

Chronic treatment with corticosterone increases the number of tyrosine hydroxylase-expressing cells within specific nuclei of the brainstem reticular formation

Cushing's syndrome is due to increased glucocorticoid levels in the body, and it is characterized by several clinical alterations which concern both vegetative and behavioral functions. The anatomical correlates of these effects remain largely unknown. Apart from peripheral effects induced by corticosteroids as counter-insular hormones, only a few reports are available concerning the neurobiology of glucocorticoid-induced vegetative and behavioral alterations. In the present study, C57 Black mice were administered daily a chronic treatment with corticosterone in drinking water. This treatment produces a significant and selective increase of TH-positive neurons within two nuclei placed in the lateral column of the brainstem reticular formation. These alterations significantly correlate with selective domains of Cushing's syndrome. Specifically, the increase of TH neurons within area postrema significantly correlates with the development of glucose intolerance, which is in line with the selective control by area postrema of vagal neurons innervating the pancreas. The other nucleus corresponds to the retrorubral field, which is involved in the behavioral activity. In detail, the retrorubral field is likely to modulate anxiety and mood disorders, which frequently occur following chronic exposure to glucocorticoids. To our knowledge, this is the first study that provides the neuroanatomical basis underlying specific symptoms occurring in Cushing's syndrome.

Transcriptional substrates underlying functional connectivity profiles of subregions within the human sensorimotor cortex

The human sensorimotor cortex has multiple subregions showing functional commonalities and differences, likely attributable to their connectivity profiles. However, the molecular substrates underlying such connectivity profiles are unclear. Here, transcriptome-neuroimaging spatial correlation analyses were performed between transcriptomic data from the Allen human brain atlas and resting-state functional connectivity (rsFC) of 24 fine-grained sensorimotor subregions from 793 healthy subjects. Results showed that rsFC of six sensorimotor subregions were associated with expression measures of six gene sets that were specifically expressed in brain tissue. These sensorimotor subregions could be classified into the polygenic- and oligogenic-modulated subregions, whose rsFC were related to gene sets diverging on their numbers (hundreds vs. dozens) and functional characteristics. First, the former were specifically expressed in multiple types of neurons and immune cells, yet the latter were not specifically expressed in any cortical cell types. Second, the former were preferentially expressed during the middle and late stages of cortical development, while the latter showed no preferential expression during any stages. Third, the former were prone to be enriched for general biological functions and pathways, but the latter for specialized biological functions and pathways. Fourth, the former were enriched for neuropsychiatric disorders, whereas this enrichment was absent for the latter. Finally, although the identified genes were commonly associated with sensorimotor behavioral processes, the polygenic-modulated subregions associated genes were additionally related to vision and dementia. These findings may advance our understanding of the functional homogeneity and heterogeneity of the human sensorimotor cortex from the perspective of underlying genetic architecture.

Long-term high fat diet consumption reversibly alters feeding behavior via a dopamine-associated mechanism in mice

Obesity is a costly, global epidemic that is perpetuated by an unhealthy diet. A significant factor in the initial consumption and maintenance of an unhealthy diet is the abundance of highly palatable, calorically dense foods. The aim of the present study is to better understand the effects of high fat diet (HFD) consumption on food valuation and preference, and to elucidate the neurobiological mechanisms mediating these effects. By using a novel food preference assay, we found that prolonged consumption of a HFD diminishes preference for and consumption of the more calorically dense food choice when two lab diets are presented. Additionally, we demonstrated that prolonged HFD consumption dampens ventral tegmental c-fos induction during hedonic feeding, implicating the mesolimbic dopamine signaling pathway as a target of HFD. Notably, both the changes in food preference and this reduced c-fos induction were reversed during withdrawal from HFD. Further, HFD-induced alterations in food preference were attenuated by exercise. Our findings suggest that prolonged HFD consumption leads to anhedonia and altered feeding choices, and this is associated with changes in mesolimbic dopamine signaling.

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

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

Does intensity or youth affect the neurobiological effect of exercise on major depressive disorder?

The purpose of this commentary is to discuss the different neurobiological effects of exercise on major depressive disorder (MDD) in children and adolescents and to provide additional explanations to this well written systematic review. This commentary highlights the effects of exercise on the hypothalamic-pituitary-adrenal (HPA) axis, which plays a crucial role in MDD. We address the questions of whether age and different exercise intensities may provide additional information on the neurobiological effects of acute or chronic exercise on MDD. Previous findings clearly suggest that the etiology of MDD is complex and multifaceted, involving numerous neurobiological systems, which are additionally influenced by these two factors.

Getting to compliance in forced exercise in rodents: a critical standard to evaluate exercise impact in aging-related disorders and disease

There is a major increase in the awareness of the positive impact of exercise on improving several disease states with neurobiological basis; these include improving cognitive function and physical performance. As a result, there is an increase in the number of animal studies employing exercise. It is argued that one intrinsic value of forced exercise is that the investigator has control over the factors that can influence the impact of exercise on behavioral outcomes, notably exercise frequency, duration, and intensity of the exercise regimen. However, compliance in forced exercise regimens may be an issue, particularly if potential confounds of employing foot-shock are to be avoided. It is also important to consider that since most cognitive and locomotor impairments strike in the aged individual, determining impact of exercise on these impairments should consider using aged rodents with a highest possible level of compliance to ensure minimal need for test subjects. Here, the pertinent steps and considerations necessary to achieve nearly 100% compliance to treadmill exercise in an aged rodent model will be presented and discussed. Notwithstanding the particular exercise regimen being employed by the investigator, our protocol should be of use to investigators that are particularly interested in the potential impact of forced exercise on aging-related impairments, including aging-related Parkinsonism and Parkinson's disease.

Neuro-hormonal effects of physical activity in the elderly

Thanks to diagnostic and therapeutic advances, the elderly population is continuously increasing in the western countries. Accordingly, the prevalence of most chronic age-related diseases will increase considerably in the next decades, thus it will be necessary to implement effective preventive measures to face this epidemiological challenge. Among those, physical activity exerts a crucial role, since it has been proven to reduce the risk of cardiovascular diseases, diabetes, obesity, cognitive impairment and cancer. The favorable effects of exercise on cardiovascular homeostasis can be at least in part ascribed to the modulation of the neuro-hormonal systems implicated in cardiovascular pathophysiology. In the elderly, exercise has been shown to affect catecholamine secretion and biosynthesis, to positively modulate the renin-angiotensin-aldosterone system and to reduce the levels of plasma brain natriuretic peptides. Moreover, drugs modulating the neuro-hormonal systems may favorably affect physical capacity in the elderly. Thus, efforts should be made to actually make physical activity become part of the therapeutic tools in the elderly.

Treadmill exercise does not change gene expression of adrenal catecholamine biosynthetic enzymes in chronically stressed rats

ABSTRACT Chronic isolation of adult animals represents a form of psychological stress that produces sympatho-adrenomedullar activation. Exercise training acts as an important modulator of sympatho-adrenomedullary system. This study aimed to investigate physical exercise-related changes in gene expression of catecholamine biosynthetic enzymes (tyrosine hydroxylase, dopamine-ß-hydroxylase and phenylethanolamine N-methyltransferase) and cyclic adenosine monophosphate response element-binding (CREB) in the adrenal medulla, concentrations of catecholamines and corticosterone (CORT) in the plasma and the weight of adrenal glands of chronically psychosocially stressed adult rats exposed daily to 20 min treadmill running for 12 weeks. Also, we examined how additional acute immobilization stress changes the mentioned parameters. Treadmill running did not result in modulation of gene expression of catecholamine synthesizing enzymes and it decreased the level of CREB mRNA in the adrenal medulla of chronically psychosocially stressed adult rats. The potentially negative physiological adaptations after treadmill running were recorded as increased concentrations of catecholamines and decreased morning CORT concentration in the plasma, as well as the adrenal gland hypertrophy of chronically psychosocially stressed rats. The additional acute immobilization stress increases gene expression of catecholamine biosynthetic enzymes in the adrenal medulla, as well as catecholamines and CORT levels in the plasma. Treadmill exercise does not change the activity of sympatho-adrenomedullary system of chronically psychosocially stressed rats.

Dopamine genes and reward dependence in adolescents with excessive internet video game play

Excessive internet video game play (EIGP) has emerged as a leading cause of behavioral and developmental problems in adolescents. Recent research has implicated the role of striatal dopaminergic system in the behavioral maladaptations associated with EIGP. This study investigates the reward-dependence characteristics in EIGP adolescents as it potentially relates to genetic polymorphisms of the dopaminergic system and temperament. Seventy-nine male EIGP adolescents and 75 age- and gender-matched healthy comparison adolescents were recruited. Associations were tested with respect to the reward-dependence (RD) scale in Cloninger's Temperament and Character Inventory and the frequencies of 3 dopamine polymorphisms: Taq1A1 allele of the dopamine D2 receptor (DRD2 Taq1A1) and Val158Met in the Catecholamine-O-Methyltransferase (COMT) genes. The Taq1A1 and low activity (COMT) alleles were significantly more prevalent in the EIGP group relative to the comparison group. The present EIGP group had significantly higher RD scores than controls. Within the EIGP group, the presence of the Taq1A1 allele correlated with higher RD scores. Our findings suggest that EIGP subjects have higher reward dependency and an increased prevalence of the DRD2 Taq1A1 and COMT alleles. In particular, the DRD2 Taq1A1 allele seems to be associated with reward dependence in EIGP adolescents.

Epigenetic vulnerability and the environmental influence on health

A growing body of evidence has drawn the attention of the scientific community by indicating the potential vulnerability to environmental changes of epigenetic mechanisms that control gene expression. Being critical components of normal development, the importance of epigenetic mechanisms for normal biology is illustrated by the fact that abnormal epigenetic patterns have increasingly been linked to the aetiology of various diseases including cancer, paediatric syndromes, autoimmune diseases, genetic disorders and even the molecular process of ageing. It is estimated that the degree of vulnerability to changes in epigenetic patterns is high during early embryonic development, a period of life in which epigenetic patterns are established and cell differentiation is intense. Moreover, increasing amounts of relevant data and information reveal that the environment might potentially impact on epigenetic patterns at every period of life. Within this context, in this study we will review the principles of epigenetic vulnerability to environmental changes, the impacts on development, the association with the origin of common diseases and also speculate about the potential of lifestyle changes to modulate epigenetic patterns and contribute to preventing common diseases.

Neurophysiological and epigenetic effects of physical exercise on the aging process

Aging is a gradual process during which molecular and cellular processes deteriorate progressively, often leading to such pathological conditions as vascular and metabolic disorders and cognitive decline. Although the mechanisms of aging are not yet fully understood, inflammation, oxidative damage, mitochondrial dysfunction, functional alterations in specific neuronal circuits and a restricted degree of apoptosis are involved. Physical exercise improves the efficiency of the capillary system and increases the oxygen supply to the brain, thus enhancing metabolic activity and oxygen intake in neurons, and increases neurotrophin levels and resistance to stress. Regular exercise and an active lifestyle during adulthood have been associated with reduced risk and protective effects for mild cognitive impairment and Alzheimer's disease. Similarly, studies in animal models show that physical activity has positive physiological and cognitive effects that correlate with changes in transcriptional profiles. According to numerous studies, epigenetic events that include changes in DNA methylation patterns, histone modification and alterations in microRNA profiles seem to be a signature of aging. Hence, insight into the epigenetic mechanisms involved in the aging process and their modulation through lifestyle interventions such as physical exercise might open new avenues for the development of preventive and therapeutic strategies to treat aging-related diseases.

The role of exercise in facilitating basal ganglia function in Parkinson's disease

Epidemiological and clinical studies have suggested that exercise is beneficial for patients with Parkinson's disease (PD). Through research in normal (noninjured) animals, neuroscientists have begun to understand the mechanisms in the brain by which behavioral training and exercise facilitates improvement in motor behavior through modulation of neuronal function and structure, called experience-dependent neuroplasticity. Recent studies are beginning to reveal molecules and downstream signaling pathways that are regulated during exercise and motor learning in animal models of PD and that are important in driving protective and/or adaptive changes in neuronal connections of the basal ganglia and related circuitry. These molecules include the neurotransmitters dopamine and glutamate (and their respective receptors) as well as neurotrophic factors (brain-derived neurotrophic factor). In parallel, human exercise studies have been important in revealing 'proof of concept' including examining the types and parameters of exercise that are important for behavioral/functional improvements and brain changes; the feasibility of incorporating and maintaining an exercise program in individuals with motor disability; and, importantly, the translation and investigation of exercise effects observed in animal studies to exercise effects on brain and behavior in individuals with PD. In this article we highlight findings from both animal and human exercise studies that provide insight into brain changes of the basal ganglia and its related circuitry and that support potentially key parameters of exercise that may lead to long-term benefit and disease modification in PD. In addition, we discuss the current and future impact on patient care and point out gaps in our knowledge where continuing research is needed. Elucidation of exercise parameters important in driving neuroplasticity, as well as the accompanying mechanisms that underlie experience-dependent neuroplasticity may also provide insights towards new therapeutic targets, including neurorestorative and/or neuroprotective agents, for individuals with PD and related neurodegenerative disorders.

Locus coeruleus galanin expression is enhanced after exercise in rats selectively bred for high capacity for aerobic activity

The neuropeptide galanin extensively coexists with norepinephrine in locus coeruleus (LC) neurons. Previous research in this laboratory has demonstrated that unlimited access to activity wheels in the home cage increases mRNA for galanin (GAL) in the LC, and that GAL mediates some of the beneficial effects of exercise on brain function. To assess whether capacity for aerobic exercise modulates this upregulation in galanin mRNA, three heterogeneous rat models were tested: rats selectively bred for (1) high intrinsic (untrained) aerobic capacity (High Capacity Runners, HCR) and (2) low intrinsic aerobic capacity (Low Capacity Runners, LCR) and (3) unselected Sprague-Dawley (SD) rats with and without free access to running wheels for 3 weeks. Following this exercise protocol, mRNA for tyrosine hydroxylase (TH) and GAL was measured in the LC. The wheel running distances between the three models were significantly different, and age contributed as a significant covariate. Both selection and wheel access condition significantly affected GAL mRNA expression, but not TH mRNA expression. GAL was elevated in exercising HCR and SD rats compared to sedentary rats while LCR rats did not differ between conditions. Overall running distance significantly correlated with GAL mRNA expression, but not with TH mRNA expression. No strain differences in GAL or TH gene expression were observed in sedentary rats. Thus, intrinsic aerobic running capacity influences GAL gene expression in the LC only insofar as actual running behavior is concerned; aerobic capacity does not influence GAL expression in addition to changes associated with running.

Catecholaminergic systems in stress: structural and molecular genetic approaches

Stressful stimuli evoke complex endocrine, autonomic, and behavioral responses that are extremely variable and specific depending on the type and nature of the stressors. We first provide a short overview of physiology, biochemistry, and molecular genetics of sympatho-adrenomedullary, sympatho-neural, and brain catecholaminergic systems. Important processes of catecholamine biosynthesis, storage, release, secretion, uptake, reuptake, degradation, and transporters in acutely or chronically stressed organisms are described. We emphasize the structural variability of catecholamine systems and the molecular genetics of enzymes involved in biosynthesis and degradation of catecholamines and transporters. Characterization of enzyme gene promoters, transcriptional and posttranscriptional mechanisms, transcription factors, gene expression and protein translation, as well as different phases of stress-activated transcription and quantitative determination of mRNA levels in stressed organisms are discussed. Data from catecholamine enzyme gene knockout mice are shown. Interaction of catecholaminergic systems with other neurotransmitter and hormonal systems are discussed. We describe the effects of homotypic and heterotypic stressors, adaptation and maladaptation of the organism, and the specificity of stressors (physical, emotional, metabolic, etc.) on activation of catecholaminergic systems at all levels from plasma catecholamines to gene expression of catecholamine enzymes. We also discuss cross-adaptation and the effect of novel heterotypic stressors on organisms adapted to long-term monotypic stressors. The extra-adrenal nonneuronal adrenergic system is described. Stress-related central neuronal regulatory circuits and central organization of responses to various stressors are presented with selected examples of regulatory molecular mechanisms. Data summarized here indicate that catecholaminergic systems are activated in different ways following exposure to distinct stressful stimuli.

Long-term compulsive exercise reduces the rewarding efficacy of 3,4-methylenedioxymethamphetamine

Although exercise has been known to regulate brain plasticity, its impact on psychostimulant reward and the associated mesolimbic dopamine system remained scarcely explored. A psychostimulant, 3,4-methylenedioxymethamphetamine (MDMA), is currently a worldwide abused drug of choice. We decided to examine the modulating effects of long-term, compulsive treadmill exercise on the hedonic value of MDMA in male C57BL/6J mice. MDMA-induced conditioned place preference (CPP) was used as a behavioral paradigm to indicate the reward efficacy of MDMA. We observed that sedentary control mice all demonstrated reliable MDMA-induced CPP with our conditioning protocol. Interestingly, pre-exposure to a treadmill exercise decreased the later MDMA-induced CPP in a running period-dependent manner. Specifically, mice undergoing a 12-week treadmill running exercise did not exhibit any approaching bias toward the MDMA-associated compartment in this CPP paradigm. Twelve weeks of treadmill running did not alter peripheral metabolism of MDMA 30min following single intraperitoneal injection of MDMA (3mg/kg). We further used microdialysis technique to study the underlying mechanisms for the impaired MDMA reward produced by the12-week exercise pre-exposure. We found that acute MDMA-stimulated dopamine release in nucleus accumbens was abolished in the exercised mice, whereas an obvious elevation of accumbal dopamine release was observed in sedentary control mice. Finally, the 12-week exercise program did not alter the protein levels of primary dopamine receptors, vesicular or membrane transporters in this area. We conclude that the long-term, compulsive exercise is effective in curbing the reward efficacy of MDMA possibly via its direct effect on reversing the MDMA-stimulated dopamine release in nucleus accumbens.

Stress-induced catecholaminergic function: transcriptional and post-transcriptional control

This review summarizes knowledge on the effects of stress on two catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT). Information is presented on differential responses of the enzymes to a variety of stressors as well as differential responses of the enzymes localized to the central nervous system vs. peripheral nervous system and tissues. Changes in mRNA and protein or activity are described, including species- and stressor-specific effects. While temporal changes in these parameters may differ for the particular stressor or enzyme, in general, maximal changes in mRNA and protein content occur at 6-8 and 24 h after stressor exposure, respectively. Elevation of TH and PNMT transcriptional activators prior to mRNA induction and nuclear run-on assays show that stress activates the genes encoding these enzymes. Yet, extents of induction of mRNA, protein and enzyme activity are often discordant depending on the stress, its duration and repetition of exposure. The extremes are concordant changes in mRNA and protein/activity vs. highly elevated mRNA with no change in protein/activity. Post-transcriptional and/or post-translational regulatory influences that may contribute to the complex effects of stress on TH, PNMT and the stress hormone epinephrine are explored.

Effects of life-long caloric restriction and voluntary exercise on age-related changes in levels of catecholamine biosynthetic enzymes and angiotensin II receptors in the rat adrenal medulla and hypothalamus

We examined if life-long mild caloric restriction (CR) alone or with voluntary exercise prevents the age-related changes in catecholamine biosynthetic enzyme levels in the adrenal medulla and hypothalamus. Ten-week-old Fisher-344 rats were assigned to: sedentary; sedentary+8% CR; or 8% CR+wheel running. Rats were euthanized at 6 or 24 months of age. Tyrosine hydroxylase (TH) mRNA expression was 4.4-fold higher in the adrenal medullae and 60% lower in the hypothalamus of old sedentary rats compared to young (p<0.01). Life-long CR reduced the age-related increase in adrenomedullary TH by 50% (p<0.05), and completely reversed the changes in hypothalamic TH. Voluntary exercise, however, had no additional effect over CR. Since angiotensin II is involved in the regulation of catecholamine biosynthesis, we examined the expressions of angiotensin II receptor subtypes in the adrenal medulla. AT(1) protein levels were 2.8-fold higher in the old animals compared to young (p<0.01), and while AT(1) levels were unaffected by CR alone, CR+wheel running decreased AT(1) levels by 50% (p<0.01). AT(2) levels did not change with age, however CR+wheel running increased its level by 42% (p<0.05). These data indicate that a small decrease in daily food intake can avert age-related changes in catecholamine biosynthetic enzyme levels in the adrenal medulla and hypothalamus, possibly through affecting angiotensin II signaling.

Norepinephrine induces BDNF and activates the PI-3K and MAPK cascades in embryonic hippocampal neurons

Both antidepressant treatment and physical exercise have been shown to increase circulating levels of norepinephine (NE) and hippocampal brain-derived neurotrophic factor (BDNF). Increases in BDNF have been shown to be associated with enhanced dendritic arborization and neuronal survival, which forms the theoretical basis of the Neurotrophin Hypothesis of antidepressant action. Using isolated embryonic hippocampal neurons and immunoblotting, we show that application of NE increases BDNF and phosphorylated Trk, and that these increases can be prevented by ERK and PI-3K inhibitors. In addition, NE-induced increases in phospho-ERK2 and PI-3K were each suppressed by a PI-3K and MAPK inhibitor, respectively. Furthermore, phosphorylation of cAMP-response element binding (CREB) protein was also increased by NE and brought down to baseline levels by MAPK and PI-3K inhibitors. And finally, because both the MAPK and PI-3K inhibitors suppress phosphorylation of both TrkB (upstream) and CREB (downstream), these results indicate that NE-induced BDNF expression follows a cyclic pathway, reminiscent of a positive feedback loop. The results of this study provide an in vitro model of the intracellular signaling mechanisms activated by NE, via ligand-G-protein-coupled receptor (GPCR)-to-BDNF-RTK transactivation, that is putatively thought to occur in vivo as a result of excitatory neural activity.

Monoamine oxidase A activity and norepinephrine level in hippocampus determine hyperwheel running in SPORTS rats

An understanding of neurological mechanisms for wheel running by rodents, especially with high exercise activity, would be applicable to a strategy for promotion of exercise motivation in humans. One of several brain regions that are candidates for the regulation of physical exercise is the hippocampus. Here we examined the running activity of Spontaneously-Running-Tokushima-Shikoku (SPORTS) rat, a new animal model for high levels of wheel-running activity, and its relation with the hippocampal norepinephrine (NE) system including the levels of NE, adrenergic receptors, and degradation enzymes for monoamines. In the hippocampus of SPORTS rats, the level of NE in extracellular fluid was augmented, whereas the level in the homogenate of the whole tissue was decreased even for sedentary conditions. Elevated extracellular NE caused downregulation of alpha(2)-adrenergic receptors in the hippocampus of SPORTS rats. Local administration of alpha(2)-adrenergic receptor antagonist yohimbine, but not of alpha(2)-agonist clonidine, into the hippocampus suppressed high running activity in SPORTS rats. The protein expression and the activity levels of monoamine oxidase A (MAOA), a critical enzyme for the degradation of NE, were decreased in the hippocampus of SPORTS rats to increase extracellular NE level. Thus, inhibition of oxidase activity in normal Wistar rats markedly increased wheel-running activity. These results indicate that decreased MAOA activity, elevation of extracellular NE, and alpha(2)-adrenergic receptors in the hippocampus determine the neural basis of the psychological regulation of exercise behavior in SPORTS rats.

Physical and cognitive activity and exercise for older adults: a review

Age-related reduction in musculoskeletal, cardiovascular, and central nervous system resilience can result in wide-ranging limitations in adaptive capacity associated with negative outcomes such as cognitive decline, increased risk of cardiovascular disease, mobility problems, and increased incidence of debilitating falls. This article reviews the benefits of both cognitive and physical activity within the broad context of multiple system resilience in adult aging. Research on a unique form of combined physical/cognitive exercise, Tai Chi Chuan, is presented. The relationship between physiological and psychological gain associated with an activity intervention program is discussed in light of principles of rehabilitation, intervention compliance, subjective and objective gain, and the hypothesized value of combining physical exercise, cognitive exercise, and relaxation into a single program designed to promote resilience in older adults.

Treadmill training ameliorates dopamine loss but not behavioral deficits in hemi-parkinsonian rats

The purpose of this study was to investigate whether locomotor training could ameliorate neurochemical changes and behavioral deficits in the 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease. It has been recently demonstrated that forelimb motor training, or brief treadmill training, can attenuate dopamine loss and some deficits in forelimb usage in this animal model. Nevertheless, it is not known whether locomotor training could result in an amelioration of locomotor deficits. Rats were lesioned with 6-OHDA injected intracerebrally and randomly assigned to one of 3 groups: early treadmill trained, late treadmill trained and untrained. Animals in the early trained group underwent 2 x 20 min treadmill sessions daily for 30 days, beginning 24 h after 6-OHDA injection. Late trained animals underwent the same training regime beginning 7 days post-injection. All animals were assessed on their abilities to perform several behavioral tasks designed to test locomotor and forelimb movement abilities prior to 6-OHDA injection and at 3 and 6 weeks post-injection. Treadmill training resulted in the attenuation of dopamine depletion in the striatum compared to non-treadmill trained animals, as measured by in vivo apomorphine-induced rotations and post-mortem dopamine analysis. Nevertheless, treadmill training produced essentially no difference in behavioral deficits on most tests compared to untrained animals. We discuss the possible reasons for the discrepancies with previous studies, including differences in lesioning, training regimes and methods of behavioral assessment. We conclude that treadmill training does not ameliorate locomotor deficits in the 6-OHDA model of Parkinson's disease, even though this same training results in attenuation of dopamine loss in the striatum.

Social hierarchy affects gene expression for catecholamine biosynthetic enzymes in rat adrenal glands

Social stressors, like other stressors, are powerful activators of the sympathoadrenomedullary system. Differential housing (single vs. group) and social defeat of rats is known to alter the activity of catecholamine-synthesizing enzymes in the medulla. The present studies examined the effect of 70 days of triad (3 rats per large cage) and individual housing of male rats on adrenal mRNA levels of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyltransferase (PNMT) and on TH protein levels. Behavioral ratings carried out at the triad formation indicated that dominant rats exhibited mostly offensive aggressive behaviors. By contrast, subordinate rats expressed primarily defensive behaviors, while the subdominant rats displayed intermediate levels of these behaviors. Overall, compared with single housing, triad housing resulted in lower gene expression for TH, DBH and PNMT and lower TH protein in the adrenals. Within triads, gene expression for these enzymes and TH protein concentration were higher in subordinate compared with dominant and subdominant rats. The dominant rats tended to have the lowest gene expression of these enzymes. These data indicate that in rodents, individual housing and a subject's social rank have a differential impact on the regulation of catecholamine biosynthesis already during the process of gene expression of catecholamine biosynthetic enzymes in the adrenals.

Exercise induces behavioral recovery and attenuates neurochemical deficits in rodent models of Parkinson's disease

Exercise is thought to improve motor function and emotional well-being in patients with Parkinson's disease (PD). However, it is not clear if the improvements are due to neurochemical alterations within the affected nigrostriatal region or result from a more general effect of exercise on affect and motivation. In this study we show that motorized treadmill running improves the neurochemical and behavioral outcomes in two rodent models of PD: the unilateral 6-hydroxydopamine (6-OHDA) rat model and bilateral 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model in aged C57bl mice. Exposure to the dopamine (DA) toxins 6-OHDA or MPTP resulted in permanent behavioral and neurochemical loss. In contrast, when lesioned animals were exposed to treadmill activity two times a day for the first 10 days post-lesion they displayed no behavioral deficits across testing days and had significant sparing of striatal DA, its metabolites, tyrosine hydroxylase, vesicular monoamine transporter, and DA transporter levels compared to lesion sedentary animals. These results demonstrate that exercise following nigrostriatal damage ameliorates related motor symptoms and neurochemical deficits in rodent models of PD.

Effects of chronic exercise and imipramine on mRNA for BDNF after olfactory bulbectomy in rat

We examined the effects of chronic activity wheel running and antidepressant treatment on brain-derived neurotrophic factor (BDNF) messenger RNA (mRNA) in multiple brain regions-hippocampal formation (HF), ventral tegmental area/substantia nigra (VTA/SN), nucleus accumbens (NAc), and piriform cortex (PFx)-after bilateral olfactory bulbectomy (OBX). Male, Long-Evans rats (n=72) underwent either sham or OBX surgery and were randomly divided into eight experimental groups in a 2 (sham vs. OBX) x 2 (sedentary vs. activity wheel)x2 (saline vs. imipramine) factorial design. Animals were killed after 21 days of treatment. Drug x exercise interaction effects were observed for HF (P=0.006-0.023) and VTA/SN (P=0.021); exercise increased BDNF mRNA in the saline treated animals but not in the imipramine treated animals. OBX did not affect BDNF mRNA in the HF or VTA/SN (P>0.05). BDNF mRNA levels in the PFx were not altered by exercise, drug, or OBX (P>0.05). These results suggest that the effect of exercise on BDNF mRNA extends beyond the HF to the mesolimbic ventral tegmental area and that the potentiation of BDNF mRNA by exercise and antidepressant pharmacotherapy, reported by other investigators, is time limited.

Effect of exercise on mRNA expression of select adrenal medullary catecholamine biosynthetic enzymes

The effect of submaximal endurance training (SET) on sympathoadrenal activity is not clear. We tested the hypothesis that SET (90 min/day, 5 days/wk, for 12 wk) elevates mRNA expression of catecholamine (CA) biosynthetic enzymes, tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DbetaH) in the adrenal medullae of adult, female Sprague-Dawley rats. SET increased TH protein level by 35%, TH activity by 62%, TH mRNA expression by 40%, and DbetaH mRNA expression by 67%. In addition, we examined the effect of SET on Fos-related antigens (FRAs), FRA-2 immunoreactivity, and activator protein (AP)-1 binding activity. SET increased AP-1 binding activity by 78%; however, it did not affect late FRAs and FRA-2 immunoreactivity. Because the regulation of neuropeptide Y (NPY) often parallels that of CAs, we also examined the effect of SET on NPY mRNA expression. Indeed, SET elevated NPY mRNA expression as well. We conclude that 1) SET elicits a pretranslational stimulatory effect on adrenomedullary CA biosynthetic enzymes, 2) another immediate early mRNA product, rather than FRA-2, may contribute to the increase in AP-1 binding activity in response to SET, and 3) SET increases NPY mRNA expression.