Stress biomarkers in rats submitted to swimming and treadmill running exercises

Wheel Running During Pregnancy Alleviates Anxiety-and Depression-Like Behaviors During the Postpartum Period in Mice: The Roles of NLRP3 Neuroinflammasome Activation, Prolactin, and the Prolactin Receptor in the Hippocampus

Despite the increase in the prevalence of postpartum depression among maternal disorder, its treatment outcomes remain suboptimal. Studies have shown that exercise can reduce postpartum depressive episodes in the mother, but the effects of exercise during pregnancy on maternal behavior and the potential mechanisms involved remain poorly understood. From the second day of pregnancy to the day of birth, dams exercised for 1 h a day by running on a controlled wheel. The maternal behaviors of the dams were assessed on postpartum day 2 to postpartum day 8. Chronic restraint stress was applied from postpartum day 2 to day 12. Blood was collected on postpartum days 3 and 8, then subjected to ELISA to determine the serum concentration of prolactin. The weight of each dam and the food intake were recorded. Anxiety- and depression-like behavioral tests were conducted, and hippocampal neuroinflammation and prolactin receptor levels were measured. The dams exhibited elevated levels of anxiety and depression, decreased serum prolactin levels, decreased prolactin receptor expression, and activation of NLRP3-mediated neuroinflammation in the hippocampus following the induction of postpartum chronic restraint stress, which were reversed with controlled wheel running during pregnancy. Overall, the findings of this study revealed that the preventive effects of exercise during pregnancy on postpartum anxiety-and depression-like behaviors were accompanied by increased serum prolactin levels, hippocampal prolactin receptor expression and hippocampal NLRP3-mediated neuroinflammation.

Time-course and muscle-specific gene expression of matrix metalloproteinases and inflammatory cytokines in response to acute treadmill exercise in rats

BACKGROUND

The extracellular matrix (ECM) of skeletal muscle plays a pivotal role in tissue repair and growth, and its remodeling tightly regulated by matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and inflammatory cytokines. This study aimed to investigate changes in the mRNA expression of MMPs (Mmp-2 and Mmp-14), TIMPs (Timp-1 and Timp-2), and inflammatory cytokines (Il-1β, Tnf-α, and Tgfβ1) in the soleus (SOL) and extensor digitorum longus (EDL) muscles of rats following acute treadmill exercise. Additionally, muscle morphology was examined using hematoxylin and eosin (H&E) staining.

METHODS AND RESULTS

Male rats were subjected to acute treadmill exercise at 25 m/min for 60 min with a %0 slope. The mRNA expression of ECM components and muscle morphology in the SOL and EDL were assessed in both sedentary and exercise groups at various time points (immediately (0) and 1, 3, 6, 12, and 24 h post-exercise). Our results revealed a muscle-specific response, with early upregulation of the mRNA expression of Mmp-2, Mmp-14, Timp-1, Timp-2, Il-1β, and Tnf-α observed in the SOL compared to the EDL. A decrease in Tgfβ1 mRNA expression was evident in the SOL at all post-exercise time points. Conversely, Tgfβ1 mRNA expression increased at 0 and 3 h post-exercise in the EDL. Histological analysis also revealed earlier cell infiltration in the SOL than in the EDL following acute exercise.

CONCLUSIONS

Our results highlight how acute exercise modulates ECM components and muscle structure differently in the SOL and EDL muscles, leading to distinct muscle-specific responses.

Age- and Sex-Dependent Effects of Moderate Exercise on Endogenous Pain Inhibition in Rats

Diffuse noxious inhibitory controls (DNICs), or the pain inhibits pain phenomenon, refer to reduced pain-like behaviors that are displayed following a noxious conditioning stimulus located far from the test stimulus and have also been referred to as "descending control of nociception" when measured in awake-behaving animals. In this study, we sought to determine the impact of moderate long-term exercise on the DCN response and determine if this effect differed across age and sex. After a six-week exercise program consisting of 30 min of moderate treadmill running 5 days a week, the animals' forepaws were injected with capsaicin, and DCN responses were assessed using thermal withdrawal latencies of the hind paw. Young, exercised male and female rats displayed prolonged DCN responses relative to their sedentary counterparts, with the young exercised male group displaying longer-lasting DCN facilitation than the young exercised females. Exercise did not impact DCN responses in either male or female aged rats. Additionally, the serum testosterone levels did not change following exercise in any group. Importantly, the levels of corticosterone did not change following the exercise program, indicating that changes in the DCN response are not due to stress-induced analgesia. Our findings suggest that moderate exercise can facilitate the DCN response in young animals, even when this exercise does not change the levels of serum testosterone.

Ageing, Cognitive Decline, and Effects of Physical Exercise: Complexities, and Considerations from Animal Models

In our ageing global population, the cognitive decline associated with dementia and neurodegenerative diseases represents a major healthcare problem. To date, there are no effective treatments for age-related cognitive impairment, thus preventative strategies are urgently required. Physical exercise is gaining traction as a non-pharmacological approach to promote brain health. Adult hippocampal neurogenesis (AHN), a unique form of brain plasticity which is necessary for certain cognitive functions declines with age and is enhanced in response to exercise. Accumulating evidence from research in rodents suggests that physical exercise has beneficial effects on cognition through its proneurogenic capabilities. Given ethical and technical limitations in human studies, preclinical research in rodents is crucial for a better understanding of such exercise-induced brain and behavioural changes. In this review, exercise paradigms used in preclinical research are compared. We provide an overview of the effects of different exercise paradigms on age-related cognitive decline from middle-age until older-age. We discuss the relationship between the age-related decrease in AHN and the potential impact of exercise on mitigating this decline. We highlight the emerging literature on the impact of exercise on gut microbiota during ageing and consider the role of the gut-brain axis as a future possible strategy to optimize exercise-enhanced cognitive function. Finally, we propose a guideline for designing optimal exercise protocols in rodent studies, which would inform clinical research and contribute to developing preventative strategies for age-related cognitive decline.

Swimming behavior indicates stress and adaptations to exercise

Introduction: Behaviors of swimming rodents are not uniform, exhibiting large variations, which may underlie the individual differences in swimming exercise-induced benefits. The study aimed to monitor individualized swimming behavior and evaluate its biological significance. Methods: A swimming tank which can monitor individualized rodent swimming behavior during exercise was established. A total of 45 mice were subjected to swimming training for 1 month (1 h per day) and the swimming behaviors of each mouse were recorded. Results: The swimming behaviors of mice displayed considerable variations in aspects of distance, velocity, and area preference. For example, nearly one-third of mice preferred to swim in central area and most of the mice exhibited an even area distribution. Long-term exercise training improved cardiac systolic function and decreased blood pressure in mice, but hardly changed swimming behaviors. Analyses of the relationship between swimming behavior and cardiovascular adaptations to exercise training revealed that swimming behavior indicated the biological effects of swimming training. Specifically, mice which preferred swimming at the central zone or were trainable in behavior during 1-month training exhibited better outcomes in cardiac function and blood pressure post long-term exercise. Mechanistically, a centralized swimming behavior indicated a smaller stress during exercise, as evidenced by a milder activation of hypothalamic-pituitary-adrenal axis. Discussion: These results suggest that swimming behavior during training indicates individualized adaptations to long-term exercise, and highlight a biological significance of swimming behavior monitoring in animal studies.

Accelerated Fear Extinction by Regular Light-Intensity Exercise: A Possible Role of Hippocampal BDNF-TrkB Signaling

PURPOSE

Growing concern exists worldwide about stress-related mental disorders, such as posttraumatic stress disorder (PTSD), often linked to hippocampal dysfunctions. Recognizing this connection, regular light-intensity exercise (LIE)-such as yoga, walking, or slow jogging-may offer a solution. Easily accessible even to vulnerable individuals, LIE has been found to enhance hippocampus-based cognitive functions through the stimulation of neurotrophic factors like brain-derived neurotrophic factor (BDNF). A prior study that demonstrated BDNF's role in extinguishing original fear memory further leads us to propose that a consistent LIE training might drive fear extinction learning, offering potential therapeutic benefits through BDNF signaling.

METHODS

Eleven-week-old Wistar rats underwent 4 wk of training under conditions of sedentary, LIE, or moderate-intensity exercise (MOE) after contextual or auditory fear conditioning. Subsequently, fear extinction tests were performed. We then administered intraperitoneal (i.p.) ANA-12, a selective antagonist of tropomyosin receptor kinase B (TrkB), or a vehicle to explore the role of BDNF signaling in exercise-induced fear extinction among the LIE rats. Following the regular exercise training, further fear extinction tests were conducted, and hippocampal protein analysis was performed using Western blotting.

RESULTS

Both LIE and MOE over 4 wk accelerated hippocampus-associated contextual fear extinction compared with sedentary. In addition, 4 wk of LIE with i.p. administered vehicle increased hippocampal BDNF and TrkB protein levels. In contrast, i.p. ANA-12 administration fully blocked the LIE-enhanced protein levels and its effect on contextual fear extinction.

CONCLUSIONS

Our findings reveal that LIE regimen promotes fear extinction learning, at least partially tied to hippocampal BDNF-TrkB signaling. This suggests that even regular light exercise could alleviate the excessive fear response in anxiety disorders and PTSD, providing hope for those affected.

Heat stress and poultry production: a comprehensive review

The impact of global warming on poultry production has gained significant attention over the years. However, our current knowledge and understanding of the mechanisms through which heat stress (HS) resulting from global warming affects the welfare, behavior, immune response, production performance, and even transgenerational effects in poultry are still incomplete. Further research is needed to delve deeper into these mechanisms to gain a comprehensive understanding. Numerous studies have investigated various biomarkers of stress in poultry, aiming to identify reliable markers that can accurately assess the physiological status and well-being of birds. However, there is a significant amount of variation and inconsistency in the results reported across different studies. This inconsistency highlights the need for more standardized methods and assays and a clearer understanding of the factors that influence these biomarkers in poultry. This review article specifically focuses on 3 main aspects: 1) the neuroendocrine and behavioral responses of poultry to HS, 2) the biomarkers of HS and 3) the impact of HS on poultry production that have been studied in poultry. By examining the neuroendocrine and behavioral changes exhibited by poultry under HS, we aim to gain insights into the physiological impact of elevated temperatures in poultry.

The Impact of Chronic Stress on Behavior and Body Mass in New Animal Models

(1) Background: Exposure to different sources of stress can have a significant effect on both psychological and physical processes. (2) Methods: The study took place over a period of 34 days and included a total of 40 animals. Regarding the exposure to chronic stressors, we opted for physiological, non-invasive stressors, e.g., running, swimming, and changes in the intensity of light. An unforeseen stress batch was also created that alternated all these stress factors. The animals were divided into five experimental groups, each consisting of eight individuals. In the context of conducting the open field test for behavioral assessment before and after stress exposure, we aimed to investigate the impact of stress exposure on the affective traits of the animals. We also monitored body mass every two days. (3) Results: The control group exhibited an average increase in weight of approximately 30%. The groups exposed to stress factors showed slower growth rates, the lowest being the running group, recording a rate of 20.55%, and the unpredictable stress group at 24.02%. The anxious behavior intensified in the group with unforeseen stress, in the one with light variations, and in the running group. (4) Conclusions: Our research validates the animal model of intermittent light exposure during the dark phase as a novel method of inducing stress. The modification of some anxiety parameters was observed; they vary according to the type of stress. Body mass was found to increase in all groups, especially in the sedentary groups, likely due to the absence of cognitive, spatial, and social stimuli except for cohabitation.

The potential protective effects of pre-injury exercise on neuroimmune responses following experimentally-induced traumatic neuropathy: a systematic review with meta-analysis

Pre-clinical evidence shows that neuropathy is associated with complex neuroimmune responses, which in turn are associated with increased intensity and persistence of neuropathic pain. Routine exercise has the potential to mitigate complications of future nerve damage and persistence of pain through neuroimmune regulation. This systematic review aimed to explore the effect of pre-injury exercise on neuroimmune responses, and other physiological and behavioural reactions following peripheral neuropathy in animals. Three electronic databases were searched from inception to July 2022. All controlled animal studies assessing the influence of an active exercise program prior to experimentally-induced traumatic peripheral neuropathy compared to a non-exercise control group on neuroimmune, physiological and behavioural outcomes were selected. The search identified 17,431 records. After screening, 11 articles were included. Meta-analyses showed that pre-injury exercise significantly reduced levels of IL-1β (SMD: -1.06, 95% CI: -1.99 to -0.13, n=40), but not iNOS (SMD: -0.71 95% CI: -1.66 to 0.25, n=82). From 72 comparisons of different neuroimmune outcomes at different anatomical locations, vote counting revealed reductions in 23 pro-inflammatory and increases in 6 anti-inflammatory neuroimmune outcomes. For physiological outcomes, meta-analyses revealed that pre-injury exercise improved one out of six nerve morphometric related outcomes (G-ratio; SMD: 1.95, 95%CI: 0.77 to 3.12, n=20) and one out of two muscle morphometric outcomes (muscle fibre cross-sectional area; SMD: 0.91, 95%CI: 0.27 to 1.54, n=48). For behavioural outcomes, mechanical allodynia was significantly less in the pre-injury exercise group (SMD -1.24, 95%CI: -1.87 to -0.61) whereas no overall effect was seen for sciatic function index. Post hoc subgroup analysis suggests that timing of outcome measurement may influence the effect of pre-injury exercise on mechanical allodynia. Risk of bias was unclear in most studies, as the design and conduct of the included experiments were poorly reported. Preventative exercise may have potential neuroprotective and immunoregulatory effects limiting the sequalae of nerve injury, but more research in this field is urgently needed.

Lactate thresholds and role of nitric oxide in male rats performing a test with forced swimming to exhaustion

The present study assessed a complex of biochemical parameters at the anaerobic threshold (AT) in untrained male Wistar rats with different times to exhaustion (Tex ) from swimming. The first group of rats was randomly divided into six subgroups and subjected to a swimming test to exhaustion without a load or with a load of 2%-10% of body weight (BW). In the first group, we established that for untrained rats, the load of 4% BW in the swimming to exhaustion test was optimal for endurance assessment in comparison with other loads. The second group of rats went through a preliminary test with swimming to exhaustion at 4% BW and was then divided into two subgroups: long swimming time (LST, Tex  > 240 min) and short swimming time (SST, Tex  < 90 min). All rats of the second group performed, for 6 days, an experimental training protocol: swimming for 20 min each day with weight increasing each day. We established that the AT was 3% BW in SST rats and 5% BW in LST rats. The AT shifted to the right on the lactate curve in LST rats. Also, at the AT in the LST rats, we found significantly lower levels of blood lactate, cortisol, and NO.

Wheel Running Exacerbates Joint Damage after Meniscal Injury in Mice, but Does Not Alter Gait or Physical Activity Levels

PURPOSE

Exercise and physical activity are recommended to reduce pain and improve joint function in patients with knee osteoarthritis (OA). However, exercise has dose effects, with excessive exercise accelerating OA development and sedentary behaviors also promoting OA development. Prior work evaluating exercise in preclinical models has typically used prescribed exercise regimens; however, in-cage voluntary wheel running creates opportunities to evaluate how OA progression affects self-selected physical activity levels. This study aimed to evaluate how voluntary wheel running after a surgically induced meniscal injury affects gait characteristics and joint remodeling in C57Bl/6 mice. We hypothesize that injured mice will reduce physical activity levels as OA develops after meniscal injury and will engage in wheel running to a lesser extent than the uninjured animals.

METHODS

Seventy-two C57Bl/6 mice were divided into experimental groups based on sex, lifestyle (physically active vs sedentary), and surgery (meniscal injury or sham control). Voluntary wheel running data were continuously collected throughout the study, and gait data were collected at 3, 7, 11, and 15 wk after surgery. At end point, joints were processed for histology to assess cartilage damage.

RESULTS

After meniscal injury, physically active mice showed more severe joint damage relative to sedentary mice. Nevertheless, injured mice engaged in voluntary wheel running at the same rates and distances as mice with sham surgery. In addition, physically active mice and sedentary mice both developed a limp as meniscal injury progressed, yet exercise did not further exacerbate gait changes in the physically active mice, despite worsened joint damage.

CONCLUSIONS

Taken together, these data indicate a discordance between structural joint damage and joint function. Although wheel running after meniscal injury did worsen OA-related joint damage, physical activity did not necessarily inhibit or worsen OA-related joint dysfunction or pain in mice.

The impact of sex and physical activity on the local immune response to muscle pain

Induction of muscle pain triggers a local immune response to produce pain and this mechanism may be sex and activity level dependent. The purpose of this study was to measure the immune system response in the muscle following induction of pain in sedentary and physically active mice. Muscle pain was produced via an activity-induced pain model using acidic saline combined with fatiguing muscle contractions. Prior to induction of muscle pain, mice (C57/BL6) were sedentary or physically active (24hr access to running wheel) for 8 weeks. The ipsilateral gastrocnemius was harvested 24hr after induction of muscle pain for RNA sequencing or flow cytometry. RNA sequencing revealed activation of several immune pathways in both sexes after induction of muscle pain, and these pathways were attenuated in physically active females. Uniquely in females, the antigen processing and presentation pathway with MHC II signaling was activated after induction of muscle pain; activation of this pathway was blocked by physical activity. Blockade of MHC II attenuated development of muscle hyperalgesia exclusively in females. Induction of muscle pain increased the number of macrophages and T-cells in the muscle in both sexes, measured by flow cytometry. In both sexes, the phenotype of macrophages shifted toward a pro-inflammatory state after induction of muscle pain in sedentary mice (M1 + M1/2) but toward an anti-inflammatory state in physically active mice (M2 + M0). Thus, induction of muscle pain activates the immune system with sex-specific differences in the transcriptome while physical activity attenuates immune response in females and alters macrophage phenotype in both sexes.

Swimming training and herbal nanoformulations as natural remedies to improve sensory-motor impairment in rat midbrain tumor models: system biology, behavioral test, and experimental validation

Motor impairment worsens health-related quality of life in patients with primary and metastatic midbrain tumors. Here, 56-male-Wistar rats were divided into eight groups: Normal group, Midbrain Tomur Model group, Model + Exe group, Model + Lipo, Model + Extract, Model + Lipo-Extract, Model + Extract-Exe, Model + Lipo-Extract + Exe. According to the aim, mid-brain tumor models were conducted by injections of the C6 glioma cell line (5 × 105 cell suspension) and stereotaxic techniques in the substantia nigra area. Furthermore, consumption of nanoformulation of herbals extract (100 mg/kg/day), crude extract (100 mg/kg/day), and swimming training (30 min, 3 days/week) as interventional protocols were performed for 6 weeks. In addition, we evaluated the effect of polyherbal nanoliposomes containing four plant extracts and swimming training on the GABArα1/TRKB/DRD2/DRD1a/TH network in the substantia nigra of the midbrain tumor rat model. Data emphasized that DRD2 might be a druggable protein with the network's highest significance cut-point effect that could modulate sensory-motor impairment. Furthermore, we found Quercetin, Ginsenosides, Curcumin, and Rutin, as bioactive compounds present in Ginseng, Matthiola incana, Turmeric, and Green-Tea extracts, could bind over the DRD2 protein with approved binding affinity scores. Based on our data, swimming training, and nanoliposome-enriched combined supplements could consider effective complementary medicine for motor impairment recovery induced by the midbrain tumor in the substantia nigra area. Hence, regular swimming training and natural medicines rich in polyphenolic bioactive components and antioxidative effects could modify and improve the dopamine receptors' function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03574-3.

Behavioral Despair Is Blocked by the Flavonoid Chrysin (5,7-Dihydroxyflavone) in a Rat Model of Surgical Menopause

Women have a high susceptibility to the negative effects of stress. Hormonal changes experienced throughout their reproductive life partially contribute to a higher incidence of anxiety and depression symptoms, particularly, during natural or surgical menopause. In preclinical research, the flavonoid chrysin (5,7-dihydroxyflavone) exerts anxiolytic- and anti-despair-like effects; however, it is unknown whether chrysin exerts a protective effect against the behavioral changes produced by acute stress on locomotor activity and behavioral despair in rats at 12-weeks post-ovariectomy. Ovariectomized female Wistar rats were assigned to eight groups: vehicle group (10% DMSO), three groups with chrysin and three groups with the same dose of allopregnanolone (0.5, 1, and 2 mg/kg), and one group with diazepam (2 mg/kg). The treatments were administered for seven consecutive days and the effects were evaluated in the locomotor activity and swimming tests. Chrysin (2 mg/kg) increased the latency to first immobility and decreased the total immobility time in the swimming test as the reference drugs allopregnanolone and diazepam (2 mg/kg); while locomotor activity prevented the behavioral changes produced by swimming. In conclusion, chrysin exerts a protective effect against the behavioral changes induced by acute stress, similarly to the neurosteroid allopregnanolone and the benzodiazepine diazepam in rats subjected to a surgical menopause model.

Swimming exercise ameliorates depressive-like behavior by anti-inflammation activity, rebalancing gut Escherichia coli and Lactobacilli

Major depressive disorder (MDD) is a common mental disease with high morbidity, recurrence and mortality and is a serious global health problem.Aerobic exercise produces beneficial effects on depression and associated comorbidities.Swimming exercise with high motor complexity may be particularly beneficial for patients with depression.We hypothesized that swimming exercise improves various types of depression-like behaviors and these effects are related to improved immune and inflammatory response by regulating microbiota-gut-brain axis.We established the Lipopolysaccharides (LPS)/Chronic unpredictable stress (CUS) mice model of depression. The forced swimming test (FST) and tail suspension test (TST) were used as predictive animal models of antidepressant-like activity.Swimming exercise significantly decreased the duration of immobility in FST and TST.We found that swimming exercise could significantly decrease the levels of pro-inflammatory cytokines in the central nervous system (CNS). Shifts in the composition of the gut microbiota were significant in depression model induced by LPS/CUS, notably as decreases in lactobacilli and increases in escherichia coli (E. coli), which were reversed byswimming exercise. Current study indicated that swimming exercise has huge potential for antidepressant therapy, and gut microbiotaplays an important role inregulating inflammation. We are pleased that current can study reveal a potentially promising method with less adverse reaction for combating depression and open up an important new area for future research.

Central injection of abscisic acid attenuates mood disorders induced by subchronic stress in male mice

Stressful life increases the risk of mental and psychological disorders and cognitive deficits. Abscisic acid (ABA) is a plant hormone that has been recently discovered in mammalians. ABA is produced in response to stressful stimuli and it can reduce anxiety-like behaviors and depression and improve cognitive function. This study was designed to evaluate the effects of microinjection of ABA on depression, anxiety, passive avoidance learning and memory deficits induced by subchronic stress. ABA (10 and 15  μ $\umu $ g/mouse, i.c.v.) was administered one week after recovery period for 4 consecutive days. A three-session forced swimming test (FST) protocol for induction of subchronic stress was administered to the mice. Exploratory, anxiety-like behavior, depression and cognitive function were assessed 24 h after the last swim stress session. The results indicated that ABA (15  μ $\umu $ g/mouse) could ameliorate anxiety and depression induced by FST. In addition, ABA had no effect on the subchronic stress-induced cognitive impairments. Taken together, the results suggest that ABA could improve anxiety and depression induced by subchronic stress.

Resistance training protects against muscle pain through activation of androgen receptors in male and female mice

ABSTRACT

Resistance training-based exercise is commonly prescribed in the clinic for the treatment of chronic pain. Mechanisms of aerobic exercise for analgesia are frequently studied, while little is known regarding resistance training mechanisms. We developed a resistance training model in mice and hypothesized resistance training would protect against development of muscle pain, mediated through the activation of androgen receptors. Activity-induced muscle hyperalgesia was produced by 2 injections of pH 5.0 stimuli with fatiguing muscle contractions. Resistance training was performed by having mice climb a ladder with attached weights, 3 times per week. Resistance training acutely increased blood lactate and prolonged training increased strength measured via forepaw grip strength and 1 repetition maximum, validating the exercise program as a resistance training model. Eight weeks of resistance training prior to induction of the pain model blocked the development of muscle hyperalgesia in both sexes. Resistance training initiated after induction of the pain model reversed muscle hyperalgesia in male mice only. A single resistance training bout acutely increased testosterone in male but not female mice. Administration of the androgen receptor antagonist flutamide (200 mg pellets) throughout the 8-week training program blocked the exercise-induced protection against muscle pain in both sexes. However, single administration of flutamide (1, 3, 10 mg/kg) in resistance-trained animals had no effect on existing exercise-induced protection against muscle pain. Therefore, resistance training acutely increases lactate and testosterone and strength overtime. Eight weeks of resistance training prevents the development of hyperalgesia through the activation of androgen receptors in an animal model of muscle pain.

Critical Problems for Research in Animal Sheltering, a Conceptual Analysis

Animal shelter research has seen significant increases in participation over the past several decades from academic organizations, private organizations, public entities, and even corporations that aims to improve shelter programs, processes, operations, and outcomes for the various stakeholders/participants involved in a shelter system (animals, humans, the community, wildlife, and the environment). These efforts are scattered through a huge variety of different research areas that are challenging to define and scope for organizations seeking to start new lines of research inquiry. This work aims to enumerate some of the most critical outstanding problems for research in animal sheltering in a conceptual framework that is intended to help direct research conversations toward the research topics of highest impact (with the highest quality outcomes possible). To this end, we define seven (7) key areas for research: animal behavior, adoptions and special needs populations, medical conditions, disease transmission, community, ecology, and wellness (one health), operations, and public-private-academic-corporate collaboration. Within each of these areas, we review specific problems and highlight examples of successes in each area in the past several decades. We close with a discussion of some of the topics that were not detailed in this manuscript but, nonetheless, deserve some mention. Through this enumeration, we hope to spur conversation around innovative methodologies, technologies, and concepts in both research and practice in animal sheltering.

Ergogenic effects of phosphatidylserine alone and combined with branched-chain amino acids in trained rats

Acute phosphatidylserine (PS) or branched-chain amino acids (BCAA) supplements alone may have an adrenocorticotropic hormone, cortisol suppressive effect and increase the testosterone/cortisol ratio, but the associated effect of these supplements during a period of high-intensity physical stress is not yet known. The study investigated the effects of chronic PS supplementation alone and combined with BCAA during high-intensity interval training (HIIT) on training volume tolerance, anabolic-catabolic balance and stress biomarkers in rats. Thirty-three rats were separated into: placebo (PLA, n=11), PS alone (n=11) and combined with BCAA (PSBCAA, n=11). Groups performed swimming sessions of HIIT (5 series × 1 min × 1 min recovery; external load equivalent to 13% of body mass) and nine recovery sessions of moderate-intensity training (30 min at 5% of body mass) alternately. One-way ANOVA was used to compare biochemical variables and two-way ANOVA was calculated to compare training volume. Training volume performed (TVP) was higher in first, fourth, fifth, sixth, and eighth HIIT sessions in the PS group in comparison to PLA (P<0.05). TVP was higher in the fourth session in PSBCAA compared to PLA. There were no differences in TVP during the sessions between PS and BCAA groups. Creatine kinase (CK) was lower in PSBCAA in comparison to PS alone (P=0.03) and PLA (P=0.04) after the experimental period. Testosterone concentration was enhanced in PSBCAA group compared to PLA (P=0.01); testosterone/corticosterone ratio was higher in PSBCAA compared to PS (P=0.05) and PLA (P=0.004) after protocol. PS combined with BCAA increases testosterone concentration and testosterone/corticosterone ratio, demonstrating an enhancement of anabolic state in trained rats.

The effect of URB597, exercise or their combination on the performance of 6-OHDA mouse model of Parkinson disease in the elevated plus maze, tail suspension test and step-down task

Parkinson disease (PD) is a progressive neurodegenerative disorder that is often accompanied by motor and psychiatric symptoms. Various approaches have been proposed for the treatment of PD. Here, we investigated the effect of a low dose of fatty acid amide hydrolase inhibitor URB597 (as an enhancer of endocannabinoid anandamide levels), exercise or their combination on some behavior alterations in PD mice lesioned by 6-hydroxydopamine (6-OHDA). The impact of swimming exercise (5×/week for 4 weeks) and URB597 (0.1 mg/kg, 2×/week for 4 weeks) on the anxiety-related behavior (elevated plus maze; EPM), depression-related behavior (tail suspension test; TST), and passive avoidance memory (step-down task) was examined in the sham and male NMRI mouse of PD model. The results show that URB597 prevented memory deficits and elicited antidepressant- and anxiolytic-like effects but did not affect hypolocomotion in the PD mice. However, URB597 did not have a significant effect on the performance of the sham mice in the performed tests. Moreover, swimming training abolished depressive- and anxiogenic-like behaviors and increased locomotion without affecting memory deficits in the PD mice. Meanwhile, swimming decreased immobility time and increased locomotion in the sham mice. Furthermore, URB597 in association with swimming training prevented all deficits induced in the PD mice, while this combination impaired memory and produced the positive effects on depression- and anxiety-related behaviors and locomotion of the sham mice. It is concluded that although URB597 or exercise alone had positive effects on most behavioral tests, their combination improved all parameters in the PD mice.

Nandrolone combined with strenuous resistance training impairs myocardial proteome profile of rats

We aimed to investigate the effects of high doses of nandrolone decanoate and resistance training (RT) on the proteomic profile of the left ventricle (LV) of rats, using a label-free quantitative approach. Male rats were randomized into four groups: untrained vehicle (UTV), trained vehicle (TV), untrained nandrolone (UTN), and trained nandrolone (TN). Rats were familiarized with the exercise training protocol (jump exercise) for one week. Jump-exercise was performed five days a week for 6 weeks, with 30 s of inter-set rest intervals. Nandrolone was administrated for 6 weeks (5 mg/kg, twice a week, via intramuscular). Systolic and diastolic arterial pressure and heart rate were measured 48 h post-training. LV was isolated and collagen content was measured. The expression of cardiac proteins was analyzed by ultra-efficiency liquid chromatography with mass spectrometry high / low collision energy (UPLC/MSE). Nandrolone and RT led to cardiac hypertrophy, even though high doses of nandrolone counteracted the RT-induced arterial pressures lowering. Nandrolone also affected the proteome profile negatively in LV of rats, including critical proteins related to biological processes (metabolism, oxidative stress, inflammation), structural function and membrane transporters. Our findings show physiological relevance since high doses of nandrolone induced detrimental effects on the proteome profile of heart tissue and hemodynamic parameters of rats. Furthermore, as nandrolone abuse has become increasingly common among recreational athletes and casual fitness enthusiasts, we consider that our findings have clinical relevance as well.

Flaxseed oil as omega-3 polyunsaturated fatty acid source modulates cortisol concentrations and social dominance in male and female guinea pigs

Flaxseed oil is an excellent source of the essential omega-3 polyunsaturated fatty acid (PUFA) alpha-linolenic acid (ALA). Omega-3 PUFAs are important neuronal components and can counteract aggressive, depressive, and anxiety-like behavior, reduce glucocorticoid (e.g. cortisol) concentrations under chronic stress but also increase acute glucocorticoid responses. As glucocorticoids per se and glucocorticoid responsiveness can modulate the establishment of dominance hierarchies, we investigated if flaxseed oil high in ALA can promote social dominance through effects on glucocorticoid concentrations. Two male and two female groups of domestic guinea pigs (n = 9 per group) were maintained on a control or a 5% (w/w) flaxseed oil diet for four weeks. Social behaviors, hierarchy indices, locomotion, and saliva cortisol concentrations were determined during basal group housing conditions and stressful social confrontations with unfamiliar individuals of the other groups. Flaxseed groups had increased basal cortisol concentrations and showed no cortisol increase during social confrontations. Cortisol concentrations in control groups significantly increased during social confrontations. Such higher cortisol responses positively affected individual hierarchy indices in control males. However, flaxseed males became dominant irrespective of cortisol concentrations. In females, the opposite was detected, namely a higher dominant status in control compared to flaxseed females. Open-field- and dark-light-tests for anxiety-like behavior revealed no pronounced differences, but flaxseed males showed the highest locomotor activity. Flaxseed oil as an ALA source sex-specifically promoted social dominance irrespective of cortisol concentrations and responses. The underlying neuronal mechanisms remain to be determined, but a sex-specific energetic advantage may have accounted for this effect.

Protective effects of forced exercise against topiramate-induced cognition impairment and enhancement of its antiepileptic activity: molecular and behavioral evidences

Propose/aim of study: Forced exercise can act as a neuroprotective factor and cognitive enhancer. The aim of the current study was to evaluate the effects of forced exercise on topiramate (TPM) induced cognitive impairment and also on TPM anti-seizure activity and neurodegeneration status after seizure.Material and method: Forty adult male rats were divided into four groups receiving normal saline, TPM (100 mg/kg), TPM in combination with forced exercise and forced exercise only respectively for 21 days. MWM test, and PTZ induced seizure were used and some oxidative, inflammatory and apoptotic biomarkers were measured for assessment of experimental animals.Results: Forced exercise in combination with TPM could abolish the TPM induced cognitive impairment and potentiates its anti-seizure activity. Also forced exercise in combination with TPM decreased malondialdehyde (MDA), tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) and Bax protein, while caused increase in superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) activities after PTZ administration.Conclusion: It seems that forced exercise could act as an adjunct therapy with TPM for management of induced cognitive impairment and can also potentiate TPM antiepileptic and neuroprotective effects.

TLR7 and IL-6 differentially regulate the effects of rotarod exercise on the transcriptomic profile and neurogenesis to influence anxiety and memory

Voluntary exercise is well known to benefit brain performance. In contrast, forced exercise induces inflammation-related stress responses and may cause psychiatric disorders. Here, we unexpectedly found that rotarod testing, a frequently applied assay for evaluating rodent motor coordination, induces anxiety and alters spatial learning/memory performance of mice. Rotarod testing upregulated genes involved in the unfolded protein response and stress responses and downregulated genes associated with neurogenesis and neuronal differentiation. It impacts two downstream pathways. The first is the IL-6-dependent pathway, which mediates rotarod-induced anxiety. The second is the Toll-like receptor 7 (TLR7)-dependent pathway, which is involved in the effect of rotarod exercise on gene expression and its impact on contextual learning and memory of mice. Thus, although rotarod exercise does not induce systemic inflammation, it influences innate immunity-related responses in the brain, controls gene expression and, consequently, regulates anxiety and contextual learning and memory.

•

Rotarod training at 5 or 10 weeks of age induces anxious behavior in an open field

•

Rotarod training upregulates IL-6 expression in the brain and results in anxiety

•

Rotarod training alters performances of test mice in spatial learning and memory

•

TLR7 controls the rotarod-impacted transcriptomic profiles and contextual memory

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

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

Enduring neuroimmunological consequences of developmental experiences: From vulnerability to resilience

The immune system is crucial for normal neuronal development and function (neuroimmune system). Both immune and neuronal systems undergo significant postnatal development and are sensitive to developmental programming by environmental experiences. Negative experiences from infection to psychological stress at a range of different time points (in utero to adolescence) can permanently alter the function of the neuroimmune system: given its prominent role in normal brain development and function this dysregulation may increase vulnerability to psychiatric illness. In contrast, positive experiences such as exercise and environmental enrichment are protective and can promote resilience, even restoring the detrimental effects of negative experiences on the neuroimmune system. This suggests the neuroimmune system is a viable therapeutic target for treatment and prevention of psychiatric illnesses, especially those related to stress. In this review we will summarise the main cells, molecules and functions of the immune system in general and with specific reference to central nervous system development and function. We will then discuss the effects of negative and positive environmental experiences, especially during development, in programming the long-term functioning of the neuroimmune system. Finally, we will review the sparse but growing literature on sex differences in neuroimmune development and response to environmental experiences.

•

The immune system is essential for development and function of the central nervous system (neuroimmune system)

•

Environmental experiences can permanently alter neuroimmune function and associated brain development

•

Altered neuroimmune function following negative developmental experiences may play a role in psychiatric illnesses

•

Positive experiences can promote resilience and rescue the effects of negative experiences on the neuroimmune system

•

The neuroimmune system is therefore a viable therapeutic target for preventing and treating psychiatric illnesses

Mechanism of exercise-induced analgesia: what we can learn from physically active animals

Physical activity has become a first-line treatment in rehabilitation settings for individuals with chronic pain. However, research has only recently begun to elucidate the mechanisms of exercise-induced analgesia. Through the study of animal models, exercise has been shown to induce changes in the brain, spinal cord, immune system, and at the site of injury to prevent and reduce pain. Animal models have also explored beneficial effects of exercise through different modes of exercise including running, swimming, and resistance training. This review will discuss the central and peripheral mechanisms of exercise-induced analgesia through different modes, intensity, and duration of exercise as well as clinical applications of exercise with suggestions for future research directions.

Interplay between hormones and exercise on hippocampal plasticity across the lifespan

The hippocampus is a brain structure known to play a central role in cognitive function (namely learning and memory) as well as mood regulation and affective behaviors due in part to its ability to undergo structural and functional changes in response to intrinsic and extrinsic stimuli. While structural changes are achieved through modulation of hippocampal neurogenesis as well as alterations in dendritic morphology and spine remodeling, functional (i.e., synaptic) changes can be noted through the strengthening (i.e., long-term potentiation) or weakening (i.e., long-term depression) of the synapses. While age, hormone homeostasis, and levels of physical activity are some of the factors known to module these forms of hippocampal plasticity, the exact mechanisms through which these factors interact with each other at a given moment in time are not completely understood. It is well known that hormonal levels vary throughout the lifespan of an individual and it is also known that physical exercise can impact hormonal homeostasis. Thus, it is reasonable to speculate that hormone modulation might be one of the various mechanisms through which physical exercise differently impacts hippocampal plasticity throughout distinct periods of an individual's life. The present review summarizes the potential relationship between physical exercise and different types of hormones (namely sex, metabolic, and stress hormones) and how this relationship may mediate the effects of physical activity during three distinct life periods, adolescence, adulthood, and senescence. Overall, the vast majority of studies support a beneficial role of exercise in maintaining hippocampal hormonal levels and consequently, hippocampal plasticity, cognition, and mood regulation.

Mild Exercise Does Not Prevent Atherosclerosis in APOE*3-Leiden.CETP Mice or Improve Lipoprotein Profile of Men with Obesity

OBJECTIVE

Exercise has been shown to improve cardiometabolic health, yet neither the molecular connection nor the effects of exercise timing have been elucidated. The aim of this study was to investigate whether ad libitum or time-restricted mild exercise reduces atherosclerosis development in atherosclerosis-prone dyslipidemic APOE*3-Leiden.CETP mice and whether mild exercise training in men with obesity affects lipoprotein levels.

METHODS

Mice were group-housed and subjected to ad libitum or time-restricted (first or last 6 hours of the active phase) voluntary wheel running for 16 weeks while on a cholesterol-rich diet, after which atherosclerosis development was assessed in the aortic root. Furthermore, nine men with obesity followed a 12-week mild exercise training program. Lipoprotein levels were measured by nuclear magnetic resonance spectroscopy in plasma collected pre and post exercise training.

RESULTS

Wheel running did not affect plasma lipid levels, uptake of triglyceride-derived fatty acids by tissues, and aortic atherosclerotic lesion size or severity. Markers of training status were unaltered. Exercise training in men with obesity did not alter lipoprotein levels.

CONCLUSIONS

Mild exercise training does not reduce dyslipidemia or atherosclerosis development in APOE*3-Leiden.CETP mice or affect lipoprotein levels in humans. Future research on the effects of (time-restricted) exercise on atherosclerosis or lipid metabolism should consider more vigorous exercise protocols.

Bright and dark sides of exercise effects on biological responses such as energy metabolism and renal function in rats with renal failure and fructose-induced glucose intolerance

In the present study, we investigated the beneficial and risky effects of exercise intended to prevent or treat lifestyle-related diseases on insulin sensitivity, lactic acid utilization, lipid metabolism, hepatic and renal oxidative stress, hepatic selenoprotein P and renal function in obese and glucose-intolerant rats with renal failure. We fed normal rats a 20% casein diet while the glucose-intolerant, obese rats received a high-fructose diet, and after then rats received single injection of vancomycin at a dose of 400 mg/kg for constructing the duplicative state of renal failure and diabetes mellitus. They were forced to run for 1 h/day, 6 days/week, for 10 weeks. Exercise reduced visceral fat and ameliorated insulin sensitivity in the high-fructose group, improved lactic acid usage efficiency, however, increased hepatic oxidative stress and complicated renal dysfunction in the normal and high-fructose fed groups with renal failure. Additionally, exercise upregulated hepatic selenoprotein P expression and enhanced renal antioxidative system in both groups. It is concluded that strictly controlled exercise conditions must be adapted to patient health states especially in view of kidney protection, and supplemental therapy is also recommended in parallel with exercise, using nutrients and vitamins for kidney protection.

Effects of exercise on biological trace element concentrations and selenoprotein P expression in rats with fructose-induced glucose intolerance

In the present study, we investigated the effects of exercise intended to prevent or treat lifestyle-related diseases on the glucose tolerance, insulin level, lactic acid utilization, muscle glycogen synthesis, hepatic and renal oxidative stress, hepatic selenoprotein P and biological trace element levels in organs of obese, glucose-intolerant rats. We fed normal, healthy rats a 20% casein diet while the glucose-intolerant, obese rats received a high-fructose diet. They were forced to run for one hour per day, six days per week, for ten weeks. Exercise reduced visceral fat and ameliorated glucose tolerance in the high-fructose group, lowered blood lactic acid levels, improved lactic acid usage efficiency, and increased oxidative stress and hepatic levels of Mn, Fe, Cu, and Zn in the normal and high-fructose groups. Additionally, exercise significantly upregulated hepatic selenoprotein P expression in both groups, however, its effect was remarkable in healthy group. On the other hand, muscle glycogen synthesis was not markedly enhanced in high-fructose-diet rats but in normal-diet rats in response to exercise. It is concluded that exercise conditions rather than exercise load must be customized and optimized for each health and disease states in advance before starting exercise training intended to prevent or treat lifestyle-related diseases.

Swimming reduces fatty acids-associated hypothalamic damage in mice

The arcuate and the paraventricular and lateral hypothalamic nuclei, related to hunger and satiety control, are generally compromised by excess fatty acids. In this situation, fatty acids cause inflammation via TLR4 (toll like receptor 4) and the nuclei become less responsive to the hormones leptin and insulin, contributing to the development of obesity. In this work, these nuclei were analyzed in animals fed with high-fat diet and submitted to swimming without and with load for two months. For this, frontal sections of the hypothalamus were immunolabelled with GFAP (glial fibrillary acidic protein), synaptophysin, IL-6 (interleukin 6) and TLR4. Also, proteins extracted from the hypothalamus were analyzed using Western blotting (GFAP and synaptophysin), fluorometric analysis for caspases 3 and 7, and CBA (cytometric bead array) for Th1, Th2, and Th17 profiles. The high-fat diet significantly caused overweight and, in the hypothalamus, decreased synapses and increased astrocytic reactivity. The swimming with load, especially 80 % of the maximum load, reduced those consequences. The high-fat diet increased TLR4 in the arcuate nucleus and the swimming exercise with 80 % of the maximum load showed a tendency of reducing this expression. Swimming did not significantly influence the inflammatory or anti-inflammatory cytokines in the hypothalamus or in plasma. The high-fat diet in sedentary animals increased the expression of caspases 3 and 7 and swimming practice reduced this increment to levels compatible with animals fed on a normal diet. The set of results conclude that the impact of swimming on the damage caused in the hypothalamus by a high-fat diet is positive. The different aspects analyzed in here point to better cellular viability and conservation of the synapses in the hypothalamic nuclei of overweight animals that practiced swimming with a load.

Biochemical aspects of KB-28 compound on physically loaded study subjects

In previous studies of actoprotective activity of 5-R-thio-tetrazolo[1,5]quinazoline derivatives in normal and complicated experimental conditions, sodium 2-(tetrazolo [1,5-c]quinazoline-5-ylthio)acetate (KB-28) was found to be the leader of the experiment. The objective of the current study was to characterize the effects of KB-28 compounds on carbohydrate and lipid exchange indices under the conditions of physical load as a possible mechanism of actoprotective effect. In the course of the experiment, the indices of carbohydrate and lipid exchange in the muscle, blood and liver of animal models were determined following a 15-day physical load course. In doing so, glucose, glycogen and total lipid concentrations were assessed. The KB-28 compound was administered daily at levels determined during the course of regular physical load normalized metabolic processes in rats. The results were then compared to a control which received intraperitoneally the equivolume 0.9% sodium chloride solution. The phenomenon of actoprotection consisted in enhancing concentrations of glycogen in skeletal muscles and liver. Compared to the control figures, this increase was 28.8% and 25.0%, accordingly. Moreover, the course of KB-28 caused a statistically significant reduction (by 32.1%) of the total serum lipid concentration in the animals under physical load. The effect may be a sign of the ability of this substance to utilize active lipolysis for improvement of the skeletal muscle performance. Having analyzed the results obtained, we can draw a conclusion that influencing the biochemical processes in the study models is one of the mechanisms of the KB-28 actoprotective effect.

Timing-Dependent Protection of Swimming Exercise against d-Galactose-Induced Aging-Like Impairments in Spatial Learning/Memory in Rats

This study was designed to investigate beneficial effects of swimming exercise training on learning/memory, synaptic plasticity and CREB (cAMP response element binding protein) expression in hippocampus in a rat model of d-galactose-induced aging (DGA). Eighty adult male rats were randomly divided into four groups: Saline Control (group C), DGA (group A), Swimming exercise before DGA (group S1), and Swimming during DGA (group S2). These four groups of animals were further divided into Morris water maze training group (M subgroup) and sedentary control group (N subgroup). Spatial learning/memory was tested using Morris water maze training. The number and density of synaptophysin (Syp) and metabotropic glutamate receptor 1 (mGluR1) in hippocampal dentate gyrus area, CREB mRNA and protein expression and DNA methylation levels were determined respectively with immunohistochemistry, western blot, real-time PCR, and MassArray methylation detection platform. We found that compared with group C, DGA rats showed aging-like poor health and weight loss as well as hippocampal neurodegenerative characteristics. Exercise training led to a time-dependent decrease in average escape latency and improved spatial memory. Exercise training group (S2M) had significantly increased swim distance as compared with controls. These functional improvements in S2M group were associated with higher Syp and mGluR1 values in hippocampus (p < 0.01) as well as higher levels of hippocampal CREB protein/mRNA expression and gene methylation. In conclusion, swimming exercise training selectively during drug-induced aging process protected hippocampal neurons against DGA-elicited degenerative changes and in turn maintained neuronal synaptic plasticity and learning/memory function, possibly through upregulation of hippocampal CREB protein/mRNA and reduction of DGA-induced methylation of CREB.

Voluntary exercise reduces both chemotherapy-induced neuropathic nociception and deficits in hippocampal cellular proliferation in a mouse model of paclitaxel-induced peripheral neuropathy

•

Paclitaxel treatment did not alter voluntary running activity.

•

Voluntary running reduced mechanical and cold allodynia induced by paclitaxel.

•

Voluntary running reduced paclitaxel-induced deficits in hippocampal cellular proliferation.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting side-effect of all major chemotherapeutic agents. Here, we explored efficacy of voluntary exercise as a nonpharmacological strategy for suppressing two distinct adverse side effects of chemotherapy treatment. We evaluated whether voluntary running would suppress both neuropathic pain and deficits in hippocampal cell proliferation in a mouse model of CIPN induced by the taxane chemotherapeutic agent paclitaxel. Mice were given free access to running wheels or were housed without running wheels during one of three different intervention phases: 1) during the onset (i.e. development phase) of paclitaxel-induced neuropathy, 2) prior to dosing with paclitaxel or its vehicle, or 3) following the establishment (i.e. maintenance phase) of paclitaxel-induced neuropathy. Paclitaxel treatment did not alter running wheel behavior relative to vehicle-treated animals in any study. Animals that engaged in voluntary running during the development phase of paclitaxel-induced neuropathy failed to display mechanical or cold hypersensitivities relative to sedentary control animals that did not have access to running wheels. A prior history of voluntary running delayed the onset of, but did not fully prevent, development of paclitaxel-induced neuropathic pain behavior. Voluntary running reduced already established mechanical and cold allodynia induced by paclitaxel. Importantly, voluntary running did not alter mechanical or cold responsivity in vehicle-treated animals, suggesting that the observed antinociceptive effect of exercise was dependent upon the presence of the pathological pain state. In the same animals evaluated for nociceptive responding, paclitaxel also reduced cellular proliferation but not cellular survival in the dentate gyrus of the hippocampus, as measured by immunohistochemistry for Ki67 and BrdU expression, respectively. Voluntary running abrogated paclitaxel-induced reductions in cellular proliferation to levels observed in vehicle-treated mice and also increased BrdU expression levels irrespective of chemotherapy treatment. Our studies support the hypothesis that voluntary exercise may be beneficial in suppressing both neuropathic pain and markers of hippocampal cellular function that are impacted by toxic challenge with chemotherapeutic agents.

Modulatory effects of swimming exercise against malathion induced neurotoxicity in male and female rats

Malathion is one of the most commonly used organophosphorus (OP) pesticides. It is important to regard that exposure to OP poisoning may cause anxiety and depression. Malathion toxicity induces cholinergic symptoms. Brain-derived neurotrophic factor (BDNF) is the most profusely expressed neurotrophin in the central nervous system; it promotes the survival of neurons. Regular exercise improves brain well-being and enhances recovery from brain Injuries. It is suggested that BDNF may mediate these effects. Therefore, this study was planned to assess the modulatory effects of regular exercise performance on brain BDNF level, cholinergic activity, oxidative stress and apoptosis in male and female rats subjected to neurotoxicity induced by malathion administration.

MATERIALS AND METHODS

Thirty-two adult male and thirty-two adult female albino rats were included in this study. The rats were divided into four equal groups (8rats). Control group, malathion treated group, exercised group, malathion exercised group. Acetylcholinesterase (AchE) activity, total antioxidant capacity (TAC), BDNF level and Caspase 3 activity were assessed.

RESULTS

Female rats had higher baseline content of BDNF in brain homogenate than male rats. Malathion administration induced a significant decrease in BDNF level in female rats and in the total antioxidant capacity in both male and female rats. A significant elevation in caspase 3 activity was detected in the malathion treated groups, with more elevation in female rats. Swimming exercise improved BDNF level, AchE activity, and apoptosis in both male and female rats in all groups. In addition, male rats were more cholinergic system responders to regular exercise than female rats.

CONCLUSION

It could be concluded that malathion induced elevation in oxidative stress and apoptosis in all rats, with reduction in BDNF level in female rats. Meanwhile, regular swimming exercise was found to improve brain health through modulation of BDNF level and cholinergic activity. It is recommended to practice regular exercise to maintain brain health. Further studies are required to clarify the involvement of sex hormones in BDNF regulation.

Reliability of blood lactate as a measure of exercise intensity in different strains of mice during forced treadmill running

Exercise has long been known to be beneficial to human health. Studies aimed at understanding the effects of exercise specifically focus on predetermined exercise intensities defined by measuring the aerobic capacity of each individual. Many disease models involving animal training often establish aerobic capacity by using the maximal lactate steady state (MLSS), a widely used method in humans that has frequently been used in rodent studies. The MLSS is defined as the highest exercise intensity at which blood lactate concentration remains constant and is roughly equivalent to 70–80% of maximal aerobic capacity. Due to our up-coming experiments investigating the effect of different exercise intensities in specific strains of tumor-bearing mice, the aim of the present study was to determine the MLSS in athymic nude (NCr nu/nu and NMRI), CDF1, and C3H mice by treadmill running at increasing speeds. However, despite thorough exercise acclimation and the use of different exercise protocols and aversive stimuli, less than half of the experiments across strains pointed towards an established MLSS. Moreover, gently prodding the mice during low to moderate intensity running caused a 30–121% (p<0.05) increase in blood lactate concentration compared to running without stimulation, further questioning the use of lactate as a measure of exercise intensity. Overall, MLSS is difficult to determine and large variations of blood lactate levels were observed depending on the exercise protocol, mice handling strategy and strain. This should be considered when planning experiments in mice using forced exercise protocols.

Intense resistance training induces pronounced metabolic stress and impairs hypertrophic response in hind-limb muscles of rats

Skeletal muscle hypertrophy is an exercise-induced adaptation, particularly in resistance training (RT) programs that use large volumes and low loads. However, evidence regarding the role of rest intervals on metabolic stress and muscular adaptations is inconclusive. Thus, we aimed to investigate the effects of a strenuous RT model (jump-training) on skeletal muscle adaptations and metabolic stress, considering the scarce information about RT models for rats. We hypothesized that jump-training induces metabolic stress and influences negatively the growth of soleus (SOL) and extensor digitorum longus (EDL) muscles of rats. Male Wistar rats (aged 60 days) were randomly assigned to non-trained or trained groups (n = 8/group). Trained rats performed jump-training during 5 days a week for 1, 3, or 5 weeks with 30 s of inter-set rest intervals. Forty-eight hours after the experimental period, rats were euthanized and blood samples immediately drawn to measure creatine kinase activity, lactate and corticosterone concentrations. Muscle weight-to-body weight ratio (MW/BW), cross-sectional area (CSA) and myosin heavy chain (MHC) isoform expression were determined. Higher lactate levels occurred after 20 min of training in weeks 1 and 3. Corticosterone levels were higher after 5 weeks of training. Jump-training had negative effects on hypertrophy of types-I and II muscle fibers after 5 weeks of training, as evidenced by decreased CSA and reduced muscle weight. Our results demonstrated that pronounced metabolic stress and impairment of muscle growth might take place when variables of exercise training are not appropriately manipulated. Lay summary Resistance training (RT) has been used to increase muscle mass. In this regard, training variables (intensity, volume, and frequency) must be strictly controlled in order to evoke substantial muscular fitness. This study shows that rats submitted to 5 weeks of intensive resistance jump-training - high intensity, large volume, and short rest intervals - present high levels of blood corticosterone associated with negative effects on hypertrophy of types-I and II muscle fibers.

Impact of chronic exercise on counteracting chronic stress-induced functional and morphological pancreatic changes in male albino rats

Chronic stress has been linked to many diseases resulted from dysfunction of both the nervous system and peripheral organ systems. Yet, the effects of chronic stress on the pancreas have received relatively little attention. This work aims to investigate the influence of chronic stress exposure on both the endocrine and exocrine pancreatic function and morphology and its possible mechanism of action, and also to evaluate the impact of chronic exercise with moderate intensity on ameliorating the stress-induced pancreatic changes. Forty adult male albino rats were used and divided into four groups: control group, exercised group (3 weeks of swimming exercise), stressed group (3 weeks of immobilization stress), and stressed group practicing exercise (3 weeks of exercise, concomitant with 21 daily sessions of stress). On the final day of the experiment, all rats were sacrificed. Biochemical, immunohistochemical, and histological studies were conducted. The results showed that chronic immobilization stress produced hyperglycemia, hyperinsulinemia, and increased homeostatic model assessment of insulin resistance index (HOMA-IR) with increasing exocrine pancreatic injury markers by increasing oxidative and inflammatory status of the pancreatic tissue. Histological study showed the injurious effect of stress on the morphology of pancreatic tissue. Physical exercise protected the pancreas from the negative effects of stress through its anti-inflammatory and anti-oxidative effects, evidenced by increasing pancreatic interleukin 10 and total antioxidant capacity and decreasing pancreatic tumor necrosis factor-alpha, and malondialdehyde with ameliorating most of the histological changes induced by stress exposure. Physical exercise effectively counteracts chronic stress-induced pancreatic changes through different mechanisms.

Exercise Attenuates Anabolic Steroids-Induced Anxiety via Hippocampal NPY and MC4 Receptor in Rats

The aim of our study was to evaluate the effects of chronic administration of nandrolone-decanoate (ND) or testosterone-enanthate (TE) in supraphysiological doses and a prolonged swimming protocol, alone and in combination with ND or TE, on anxiety-like behavior in rats. We investigated the immunohistochemical alterations of the hippocampal neuropeptide Y (NPY) and melanocortin 4 receptor (MC4R) neurons, as a possible underlying mechanism in a modulation of anxiety-like behavior in rats. Both applied anabolic androgenic steroids (AASs) induced anxiogenic effect accompanied with decreased serum and hippocampal NPY. The exercise-induced anxiolytic effect was associated with increased hippocampal NPY expression. ND and TE increased the number of MC4R, while the swimming protocol was followed by the reduction of MC4R in the CA1 region of the hippocampus. However, NPY/MC4R ratio in hippocampus was lowered by AASs and elevated by exercise in all hippocampal regions. An augmentation of this ratio strongly and positively correlated to increased time in open arms of elevated plus maze, in the context that indicates anxiolytic effect. Our findings support the conclusion that alterations in both hippocampal NPY and MC4R expression are involved in anxiety level changes in rats, while their quantitative relationship (NPY/MC4R ratio) is even more valuable in the estimation of anxiety regulation than individual alterations for both NPY and MC4R expression in the hippocampus.

The Impact of Hippocampal Sex Hormones Receptors in Modulation of Depressive-Like Behavior Following Chronic Anabolic Androgenic Steroids and Exercise Protocols in Rats

The aim of this study was to evaluate alterations in depressive-like behaviors in rats following chronic administration of a supraphysiological dose of anabolic androgenic steroids (AASs) as well as exposure to a prolonged exercise protocol. The role of hippocampal sex hormones receptors in the modulation of depressive-like behavior was also assessed. A total of 48 male Wistar albino rats were divided into six groups: control, exercise (1 h/day, five consecutive days), nandrolone-decanoate (ND, 20 mg/kg/week, in a single dose), exercise plus ND, testosterone-enanthate (TE, 20 mg/kg/week, in a single dose), and exercise plus TE. After the 6-week protocols were complete, the rats underwent behavioral testing in the tail suspension test (TST). Rats were sacrificed for the collection of blood samples, to determine sex hormones levels, and isolation of the hippocampus, to determine [androgen receptors (AR) and estrogen receptors α (ERα)] expression. ND and TE treatment induced significant depressive-like behavior, opposing the antidepressant effect of exercise. Chronic TE administration elevated testosterone (T) and dihydrotestosterone (DHT) serum levels, and this was augmented by exercise. In contrast, ND and exercise alone did not alter T or DHT levels. There were no changes in serum estradiol levels in any of the groups. Immunohistochemical analysis showed that exercise reduced AR immunoreactivity in all hippocampal regions and increased the ERα expression in the CA1, dentate gyrus (DG), and total hippocampal sections, but not in the CA2/3 region. AASs administration increased AR expression in all hippocampal regions, although not the total hippocampal section in the TE group and did not significantly decrease ERα. The hippocampal AR/ERα expression index was lowered while parvalbumin (PV)-immunoreactivity was enhanced by exercise. AASs administration increased the AR/ERα index and reduced PV-immunoreactivity in the hippocampus. The number of PV-immunoreactive neurons negatively correlated with the antidepressant effects and the AR/ERα ratio. Our results suggest a potential role of the numerical relationship between two sex hormones receptors (stronger correlation than for each individual receptor) in the regulation of depressive-like behavior via the hippocampal GABAergic system in rats, which allow better understanding of the hippocampal sex hormones receptors role in modulation of depressive-like behavior.

Forced Swim Reliability for Exercise Testing in Rats by a Tethered Swimming Apparatus

To assess the physical capacity of rats in forced swim tests, the animal should perform a continuous activity (CON) at the surface to avoid apnea. Bobbing movement (BOB), vigorous paddling known as climbing (CLI), and diving activity (DIV) are inadequate swimming patterns known to increase the exercise intensity variability, impairing the test reliability. Thus, the exercise work accomplished and related physiological variables, such as the blood lactate concentration, may be unreproducible in forced swim. This study aimed to verify the exercise work reproducibility in rats with a 30-min test–retest at maximal lactate steady state (MLSS) intensity using a tethered-swimming apparatus that analyzes swimming patterns by the direct measurement of swimming force. Additionally, it was determined the swimming force and duration of CON, BOB, CLI, and DIV at physiologically different exercise-intensities. The swimming force at MLSS (n = 64) was 38 ± 7 gf.Kg^-1, while the blood lactate concentration was 4.2 ± 1.6 mmol.L^-1. In the test–retest (N = 23), swimming force (36.6 ± 7 gf.Kg^-1 vs. 36.4 ± 7 gf.Kg^-1) and blood lactate concentration (4.7 ± 1.7 mmol.L^-1 vs. 4.2 ± 1.7 mmol.l^-1) were similar, but only the swimming force was highly correlated (0.90 and 0.31). Although it was not statistically different, the swimming force for CON tends to be slightly lower than CLI and slightly higher than BOB independently of exercise-intensity. The CON pattern predominates (∼52.8 ± 18%) at intensities below and of MLSS but BOB was the swimming pattern more often observed above MLSS-intensity (52.6 ± 18%). The present study used a tethered swimming apparatus to investigate the reliability of forced swim tests for exercise testing in rats and better understand the swimming patterns when determining the MLSS, but the results can be extended to any study that rely on forced swim for exercise testing and training. The result suggests that, at least at intensities of physiological stability, the exercise work accomplished by rats is reproducible in forced swim, but the blood lactate concentration seems to be affected by other factors, such as the apnea and stress caused by the possibility of drowning, besides the exercise-intensity.

Keto analogues and amino acid supplementation and its effects on ammonaemia during extenuating endurance exercise in ketogenic diet-fed rats

Keto analogues and amino acids (KAAA) supplementation can reduce blood ammonia concentrations in athletes undergoing high-intensity exercise under both ketogenic and thermoneutral conditions. This study evaluated the acute effects of KAAA supplementation on ammonia metabolism during extenuating endurance exercise in rats fed a ketogenic diet. In all, eighty male Fischer rats at 90 d of age were divided into eight groups, and some were trained using a swimming endurance protocol. A ketogenic diet supplemented with keto analogues was administered for 10 d. Administration of the ketogenic diet ended 3 d before the exhaustion test (extenuating endurance exercise). A ketogenic diet plus KAAA supplementation and extenuating endurance exercise (trained ketogenic diet supplemented with KAAA (TKKa)) increased blood ammonia concentrations by approximately 50 % compared with the control diet (trained control diet supplemented with KAAA (TCKa)) and similar training (effect size=1·33; statistical power=0·50). The KAAA supplementation reduced blood urea concentrations by 4 and 18 % in the control and ketogenic diet groups, respectively, compared with the groups fed the same diets without supplementation. The trained groups had 60 % lower blood urate concentrations after TCKa treatment than after TKKa treatment. Our results suggest that KAAA supplementation can reduce blood ammonia concentrations after extenuating endurance exercise in rats fed a balanced diet but not in rats fed a ketogenic diet.

The Impact of Exercise in Rodent Models of Chronic Pain

PURPOSE OF REVIEW

Physical activity is increasingly recommended for chronic pain. In this review, we briefly survey recent, high-quality meta-analyses on the effects of exercise in human chronic pain populations, followed by a critical discussion of the rodent literature.

RECENT FINDINGS

Most meta-analytical studies on the effects of exercise in human chronic pain populations describe moderate improvements in various types of chronic pain, despite substantial variability in the outcomes reported in the primary literature. The most consistent findings suggest that while greater adherence to exercise programs produces better outcomes, there is minimal support for the superiority of one type of exercise over another. The rodent literature similarly suggests that while regular exercise reduces hypersensitivity in rodent models of chronic pain, exercise benefits do not appear to relate to either the type of injury or any particular facet of the exercise paradigm. Potential factors underlying these results are discussed, including the putative involvement of stress-induced analgesic effects associated with certain types of exercise paradigms. Exercise research using rodent models of chronic pain would benefit from increased attention to the role of stress in exercise-induced analgesia, as well as the incorporation of more clinically relevant exercise paradigms.