Hypothalamus, hypertension, and exercise

Targeting the gut microbiota-related metabolites for osteoporosis: The inextricable connection of gut-bone axis

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass, destruction of bone microstructure, raised bone fragility, and enhanced risk of fractures. The correlation between gut microbiota and bone metabolism has gradually become a widespread research hotspot in recent years, and successive studies have revealed that the alterations of gut microbiota and its-related metabolites are related to the occurrence and progression of osteoporosis. Moreover, several emerging studies on the relationship between gut microbiota-related metabolites and bone metabolism are also underway, and extensive research evidence has indicated an inseparable connection between them. Combined with latest literatures and based on inextricable connection of gut-bone axis, this review is aimed to summarize the relation, potential mechanisms, application strategies, clinical application prospects, and existing challenges of gut microbiota and its-related metabolites on osteoporosis, thus updating the knowledge in this research field and providing certain reference for future researches.

Gut Microbiota Perturbation in Early Life Could Influence Pediatric Blood Pressure Regulation in a Sex-Dependent Manner in Juvenile Rats

The present study aimed to investigate whether gut dysbiosis induced by ceftriaxone in early life could influence pediatric blood pressure regulation in childhood with or without exposure to a high-fat diet (HFD). Sixty-three newborn pups of Sprague-Dawley rats were administered ceftriaxone sodium or saline solution until weaning at 3 weeks, and the rats were fed a HFD or regular diet from 3 to 6 weeks. Tail-cuff blood pressure, the expression levels of genes of the renin-angiotensin system (RAS), the concentrations of IL-1β, IL-6, and TNF-α in the colon and prefrontal cortex, and the composition of fecal microbiota were analyzed. Ceftriaxone treatment significantly increased the diastolic blood pressure of male rats at 3 weeks. At 6 weeks, systolic blood pressure (SBP) was significantly increased only in ceftriaxone treated male rats fed with HFD. The RAS showed increased activation in the kidney, heart, hypothalamus, and thoracic and abdominal aorta of male rats, but only in the kidney, heart, and hypothalamus of female rats. HFD-fed female rats showed a decreased level of IL-6 in the colon. α diversity of gut microbiota decreased and the Firmicutes to Bacteroidetes ratio increased in both male and female rats at 3 weeks; however, these parameters recovered to various degrees in female rats at 6 weeks. These results revealed that early-life gut dysbiosis induced by antibiotics combined with a HFD in childhood could be involved in pediatric blood pressure regulation and an increase in SBP in juvenile rats, and these effects occurred in a sex-dependent manner.

A narrative review of the moderating effects and repercussion of exercise intervention on osteoporosis: ingenious involvement of gut microbiota and its metabolites

Osteoporosis (OP) is a systemic bone disease characterized by the decreased bone mass and destruction of bone microstructure, which tends to result in the enhanced bone fragility and related fractures, as well as high disability rate and mortality. Exercise is one of the most common, reliable and cost-effective interventions for the prevention and treatment of OP currently, and numerous studies have revealed the close association between gut microbiota (GM) and bone metabolism recently. Moreover, exercise can alter the structure, composition and abundance of GM, and further influence the body health via GM and its metabolites, and the changes of GM also depend on the choice of exercise modes. Herein, combined with relevant studies and based on the inseparable relationship between exercise intervention-GM-OP, this review is aimed to discuss the moderating effects and potential mechanisms of exercise intervention on GM and bone metabolism, as well as the interaction between them.

A Critical Role for the Paraventricular Nucleus of the Hypothalamus in the Regulation of the Volume Reflex in Normal and Various Cardiovascular Disease States

PURPOSE OF REVIEW

This review focuses on studies implicating forebrain neural pathways and neuromodulator systems, particularly, the nitric oxide system within the paraventricular nucleus of the hypothalamus in regulating neurohumoral drive, autonomic pathways, and fluid balance.

RECENT FINDINGS

Accumulating evidence from animals with experimental models of hypertension and heart failure as well as humans with hypertension suggests that alterations in central neural pathways, particularly, within the PVN neuromodulated by neuronal nitric oxide, are involved in regulating sympathetic outflow particularly to the kidney resulting in alterations in fluid balance commonly observed in hypertension and heart failure states. The characteristics of the hypertensive and heart failure states include alterations in neuronal nitric oxide within the PVN to cause an increase in renal sympathetic nerve activity to result in sodium and fluid retention in these diseases. A comprehensive understanding of these mechanisms will enhance our ability to treat hypertensive and heart failure conditions and their cardiovascular complications more efficiently.

Combined effects of angiotensin receptor blocker use and physical training in hypertensive men

PURPOSE

Pharmacological (angiotensin II receptor type 1 receptor blocker use) and non-pharmacological treatment (physical aerobic exercise) are important strategies to reduces blood pressure and control arterial hypertension; however, only few clinical studies have evaluated their combined effects on autonomic cardiovascular control. Therefore, we investigated the effect of a combination intervention that involved losartan administration and physical aerobic training on autonomic cardiovascular control.

METHODS

Thirty-two men (aged 40 to 60 years) were assigned into two groups: normotensive group, without any pharmacological treatment (NG, N = 16), or hypertensive group, with losartan administration (HG, N = 16). They underwent a physical aerobic training for 16 weeks, thrice a week. Hemodynamic parameters, heart rate variability (HRV), blood pressure variability, and spontaneous baroreflex sensitivity (BRS) were measured before and after training.

RESULTS

Before training, both the groups showed similar values of hemodynamic parameters. However, the HG showed decreased BRS and HRV, characterized by reduction in sympathetic (p = .02) and vagal (p < .001) modulation. After training, the NG exhibited decreased heart rate (HR) at rest (p < .001), whereas the HG showed decreased HR at rest (p < .001) and blood pressure (BP) (p = .001). The HG showed decreased sympathetic modulation (p = .02) and increased BRS (p < .001) and vagal modulation (p < .001), but HRV (p < .001) and BRS gain (p < .001) remained significantly lower when compared to the NG.

CONCLUSIONS

Physical aerobic training was essential to improve the BRS and HRV cardiac autonomic modulation in the HG. However, it was not sufficient to normalize the analyzed autonomic parameters.

Heart Rate Variability and Cardiovascular Fitness: What We Know so Far

Fluctuation analysis in intervals between heartbeats provides important indices related to autonomic modulation of heart rate variability (HRV). These indices are considered predictors of morbidity and mortality as they are frequently altered in patients with chronic degenerative diseases, especially in those with cardiovascular and metabolic diseases. Similarly, a reduction in HRV is common with aging. In all cases, cardiovascular fitness is often reduced to below the predicted values. In turn, increases in cardiovascular fitness through regular physical exercise, especially aerobic exercise, represent an important therapeutic tool capable of promoting positive adjustments in cardiac autonomic modulation. These adjustments are characterized by reduced sympathetic modulatory influence and/or increased vagal modulatory influence on the heart, increasing the HRV. Therefore, several methodological tools have been used to assess the degree of impairment of autonomic modulation and the therapeutic effects of physical exercise. In contrast, establishment of strict protocols in experimental design is a main challenge in establishing HRV analysis as a robust parameter for evaluating cardiovascular homeostasis. Thus, this review aimed to contribute to the understanding of autonomic modulation of HRV and its relationship with cardiovascular fitness, highlighting the advances made thus far, the applicability of analysis tools, and the confounding factors observed frequently.

Clinical Epidemiology of Systolic and Diastolic Orthostatic Hypotension in Patients on Peritoneal Dialysis

Blood pressure changes upon standing reflect a hemodynamic response, which depends on the baroreflex system and euvolemia. Dysautonomia and fluctuations in blood volume are hallmarks in kidney failure requiring replacement therapy. Orthostatic hypotension has been associated with mortality in hemodialysis patients, but neither this relationship nor the impact of changes in blood pressure has been tested in patients on peritoneal dialysis. We investigated both these relationships in a cohort of 137 PD patients. The response to orthostasis was assessed according to a standardized protocol. Twenty-five patients (18%) had systolic orthostatic hypotension, and 17 patients (12%) had diastolic hypotension. The magnitude of systolic and diastolic BP changes was inversely related to the value of the corresponding supine BP component (r = -0.16, p = 0.056 (systolic) and r = -0.25, p = 0.003 (diastolic), respectively). Orthostatic changes in diastolic, but not in systolic, BP were linearly related to the death risk (HR (1 mmHg reduction): 1.04, 95% CI 1.01-1.07, p = 0.006), and this was also true for CV death (HR: 1.08, 95% CI 1.03-1.12, p = 0.001). The strength of this association was not affected by further data adjustment (p ≤ 0.05). These findings suggest that independent of the formal diagnosis of orthostatic hypotension, even minor orthostatic reductions in diastolic BP bear an excess death risk in this population.

"The addition of naltrexone alters cerebral glucose uptake following acute forced swimming"

Endogenous opioid release has been linked to exercise. We investigated if opioid blockade following forced swimming, a common model of rodent exercise, influenced cerebral glucose metabolism in mice. PET scan was used to assess the uptake of Fludeoxyglucose (FDG-18), a marker of cerebral glucose metabolism in 19 regions of the interest in the brain following: forced swimming, an acute dose of the opioid receptor blocker naltrexone or a combination of both. Forced swimming increased glucose uptake in the cerebellum, while naltrexone + forced swimming increased glucose uptake in the hypothalamus, forebrain, septum and amygdala. This suggests that opioid blockade alters the typical pattern of cerebral glucose uptake following forced swimming in mice in certain areas of the brain.

Acute and long-term treadmill running differentially induce c-Fos expression in region- and time-dependent manners in mouse brain

Acute and long-term exercise differentially affect brain functions. It has been suggested that neuronal activation is one of the mechanisms for exercise-induced enhancement of brain functions. However, the differential effects of acute and long-term exercise on the spatial and temporal profiles of neuronal activation in the brain have been scarcely explored. In this study, we profiled the expression of c-Fos, a marker of neuronal activation, in selected 26 brain regions of 2-month-old male C57/B6 mice that received either a single bout of treadmill running (acute exercise) or a 4-week treadmill training (long-term exercise) at the same duration (1 h/day) and intensity (10 m/min). The c-Fos expression was determined before, immediately after, and 2 h after the run. The results showed that acute exercise increased the densities of c-Fos⁺ cells in the ventral hippocampal CA1 region, followed by (in a high to low order) the primary somatosensory cortex, other hippocampal subregions, and striatum immediately after the run; significant changes remained evident in the hippocampal subregions after a 2-h rest. Long-term exercise increased the densities of c-Fos⁺ cells in the striatum, followed by the primary somatosensory, primary and secondary motor cortices, hippocampal subregions, hypothalamic nuclei, and lateral periaqueductal gray; significant changes remained evident in the striatum, hippocampal subregions, hypothalamic nuclei, and lateral periaqueductal gray after a 2-h rest. Interestingly, the densities of c-Fos⁺ cells in the substantia nigra and ventral tegmental area only increased after a 2-h rest after the run in the long-term exercise group. The densities of c-Fos⁺ cells were positively correlated with the expression of brain-derived neurotrophic factor in the selected brain regions. In conclusion, both acute and long-term treadmill running at mild intensity induce c-Fos expression in the limbic system and movement-associated cortical and subcortical regions, with long-term exercise involving more brain regions (i.e., hypothalamus and periaqueductal gray) and longer lasting effects.

Stress-sensitive arterial hypertension, haemodynamic changes and brain metabolites in hypertensive ISIAH rats: MRI investigation

NEW FINDINGS

What is the central question of this study? Stress-sensitive arterial hypertension is considered to be controlled by changes in central and peripheral sympathetic regulating mechanisms, which eventually result in haemodynamic alterations and blood pressure elevation. Therefore, study of the early stages of development of hypertension is of particular interest, because it helps in understanding the aetiology of the disease. What is the main finding and its importance? Non-invasive in vivo investigation in ISIAH rats demonstrated that establishment of sustainable stress-sensitive hypertension is accompanied by a decrease in prefrontal cortex activity and mobilization of hypothalamic processes, with considerable correlations between haemodynamic parameters and individual metabolite ratios. The study of early development of arterial hypertension in association with emotional stress is of great importance for better understanding of the aetiology and pathogenesis of the hypertensive disease. Magnetic resonance imaging (MRI) was applied to evaluate the changes in haemodynamics and brain metabolites in 1- and 3-month-old inherited stress-induced arterial hypertension (ISIAH) rats (10 male rats) with stress-sensitive arterial hypertension and in control normotensive Wistar Albino Glaxo (WAG) rats (eight male rats). In the 3-month-old ISIAH rats, the age-dependent increase in blood pressure was associated with increased blood flow through the renal arteries and decreased blood flow in the lower part of the abdominal aorta. The renal vascular resistance in the ISIAH rats decreased during ageing, although at both ages it remained higher than the renal vascular resistance in WAG rats. An integral metabolome portrait demonstrated that development of hypertension in the ISIAH rats was associated with an attenuation of the excitatory and energetic activity in the prefrontal cortex, whereas in the WAG rats the opposite age-dependent changes were observed. In contrast, in the hypothalamus of 3-month-old ISIAH rats, an increase in energetic activity and prevalence of excitatory over inhibitory neurotransmitters was noticed. The blood flow through the main arteries showed a positive correlation with glutamate and glutamine levels in the hypothalamus and a negative correlation with the hypothalamic GABA level. The blood pressure values were positively correlated with hypothalamic choline levels. Thus, the early development of stress-sensitive hypertension in the ISIAH rats is accompanied by considerable changes both in brain metabolite ratios and in the parameters of blood flow through the main arteries.

Amlodipine and enalapril promote distinct effects on cardiovascular autonomic control in spontaneously hypertensive rats: the role of aerobic physical training

BACKGROUND

We compared the autonomic and hemodynamic cardiovascular effects of amlodipine and enalapril treatment associated with an aerobic physical training program on spontaneously hypertensive rats.

METHODS

Eighteen-week-old (n = 48) spontaneously hypertensive rats were assigned to one of two groups: sedentary (n = 24) and trained (n = 24) through a 10-week swimming training program. Each group was subdivided into three groups (n = 8): control (vehicle group), amlodipine (amlodipine group; 10 mg/kg per day) and enalapril (enalapril group; 10 mg/kg per day) (both for 10 weeks). We cannulated the femoral artery and vein of all animals for recording arterial pressure and injecting drugs, respectively. Autonomic assessment was performed by double blockade with propranolol and atropine, analysis of heart rate variability (HRV), systolic arterial pressure variability and baroflex sensitivity.

RESULTS

Arterial pressure reduction was more prominent in the sedentary and trained enalapril groups. Amlodipine sedentary group presented important autonomic adjustments characterized by a predominance of vagal tone in cardiac autonomic balance, increased HRV associated with sympathetic autonomic modulation reduction and increased vagal autonomic modulation, and increased baroflex sensitivity. All findings were not potentialized by physical training. In turn, the enalapril trained group, but not its sedentary counterpart, also had vagal tone prevalence in cardiac autonomic balance, increased HRV, increased baroflex sensitivity and decreased low-frequency band in systolic arterial pressure variability.

CONCLUSION

Amlodipine was more effective in promoting beneficial autonomic cardiovascular adaptations in sedentary animals. In contrast, enalapril achieved better autonomic results only when combined with aerobic physical training.

Aerobic physical training increases contractile response and reduces cardiac fibrosis in rats subjected to early ovarian hormone deprivation

We investigated the effects of early ovarian hormone deprivation on the heart and the role of physical training in this condition using different approaches: cardiac autonomic tone, contractility, morphology and function, and cardiac fibrosis. Female Wistar rats ( n = 48) were assigned into two groups: ovariectomized (Ovx; 10-wk-old) and control rats (Sham; 10-wk-old). Each group was further divided into two subgroups, sedentary and trained (aerobic training by swimming for 10 wk). The sedentary groups showed similar cardiac autonomic tone values; however, only the Sham group had an increase in vagal participation for the determination of the basal heart rate after physical training. The contractile responses to cardiac β-agonists of the sedentary groups were similar, including an increased response to a β1-agonist (dobutamine) observed after physical training. The Ovx sedentary group presented changes in cardiac morphology, which resulted in decreases in the ejection fraction, fractional shortening, and cardiac index compared with the Sham sedentary group. Physical training did little to alter these findings. Moreover, histology analysis showed a significant increase in cardiac fibrosis in the sedentary Ovx group, which was not observed in the trained Ovx group. We conclude that early ovarian hormone deprivation in rats impairs autonomic control, cardiac morphology, and cardiac function and increases cardiac fibrosis; however, it does not affect the contractility induced by dobutamine and salbutamol. Furthermore, this model of physical training prevented an increase in fibrosis and promoted an increase in the cardiac contractile response but had little effect on cardiac autonomic control or morphological and functional parameters.

CNS neuroplasticity and salt-sensitive hypertension induced by prior treatment with subpressor doses of ANG II or aldosterone

Although sensitivity to high dietary NaCl is regarded to be a risk factor for cardiovascular disease, the causes of salt-sensitive hypertension remain elusive. Previously, we have shown that rats pretreated with subpressor doses of either ANG II or aldosterone (Aldo) show sensitized hypertensive responses to a mild pressor dose of ANG II when tested after an intervening delay. The current studies investigated whether such treatments will induce salt sensitivity. In studies employing an induction-delay-expression experimental design, male rats were instrumented for chronic mean arterial pressure (MAP) recording. In separate experiments, ANG II, Aldo, or vehicle was delivered either subcutaneously or intracerebroventricularly during the induction. There were no sustained differences in BP during the delay prior to being given 2% saline. While consuming 2% saline during the expression, both ANG II- and Aldo-pretreated rats showed significantly greater hypertension. When hexamethonium was used to assess autonomic control of MAP, no differences in the decrease of MAP in response to ganglionic blockade were detected during the induction. However, during the expression, the fall was greater in sensitized rats. In separate experiments, brain tissue that was collected at the end of delay showed increases in message or activation of putative markers of neuroplasticity (i.e., brain-derived neurotrophic factor, p38 mitogen-activated protein kinase, and cAMP response element-binding protein). These experiments demonstrate that prior administration of nonpressor doses of either ANG II or Aldo will induce salt sensitivity. Collectively, our findings indicate that treatment with subpressor doses of ANG II and Aldo initiate central neuroplastic changes that are involved in hypertension of different etiologies.

Chronic exercise modulates RAS components and improves balance between pro- and anti-inflammatory cytokines in the brain of SHR

Recently, exercise has been recommended as a part of lifestyle modification for all hypertensive patients; however, the precise mechanisms of its effects on hypertension are largely unknown. Therefore, this study aimed to investigate the mechanisms within the brain that can influence exercise-induced effects in an animal model of human essential hypertension. Young normotensive WKY rats and SHR were given moderate-intensity exercise for 16 weeks. Blood pressure was measured bi-weekly by tail-cuff method. Animals were then euthanized; paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM), important cardiovascular regulatory centers in the brain, were collected and analyzed by real-time RT-PCR, Western blot, EIA, and fluorescent microscopy. Exercise of 16-week duration attenuated systolic, diastolic, and mean arterial pressure in SHR. Sedentary SHR exhibited increased pro-inflammatory cytokines (PICs) and decreased anti-inflammatory IL-10 levels in the PVN and RVLM. Furthermore, SHR(sed) rats exhibited elevated levels of ACE, AT1R, and decreased levels of ACE2 and receptor Mas in the PVN and RVLM. Chronic exercise not only prevented the increase in PICs (TNF-α, IL-1β), ACE, and AT1R protein expression in the brain of SHR, but also dramatically upregulated IL-10, ACE2, and Mas receptor expression in SHR. In addition, these changes were associated with reduced plasma AngII levels, reduced neuronal activity, reduced NADPH-oxidase subunit gp91(phox) and inducible NO synthase in trained SHRs indicating reduced oxidative stress. These results suggest that chronic exercise not only attenuates PICs and the vasoconstrictor axis of the RAS but also improves the anti-inflammatory defense mechanisms and vasoprotective axis of the RAS in the brain, which, at least in part, explains the blood pressure-lowering effects of exercise in hypertension.

Voluntary exercise alters GABA(A) receptor subunit and glutamic acid decarboxylase-67 gene expression in the rat forebrain

Voluntary exercise improves stress coping and lowers anxiety. Because of the role of GABA in these processes, we investigated changes in the central GABAergic system in rats with free access to a running wheel for 4 weeks. The control animals had no access to a running wheel. Using insitu hybridisation histochemistry, we studied changes in gene expression of various GABA(A) receptor subunits as well as the GABA-synthesising enzyme glutamic acid decarboxylase-67 (GAD67) in the forebrain. There were region-specific decreases in alpha2, beta3 and gamma2 subunit mRNA expression and region-specific increases in beta1 subunit expression. The alpha5 and delta subunits, in the forebrain specifically associated with extrasynaptic GABA(A) receptors in the hippocampus, showed differential increases in expression levels. Expression of GAD67 mRNA was increased in many forebrain regions including all hippocampal cell layers, peri-paraventricular nucleus, bed nucleus stria terminalis, nucleus accumbens core and motor cortex, suggesting that long-term voluntary exercise enhances forebrain GABA synthesis capacity but in a region-specific manner. Thus, regular performance of exercise results in extensive changes in the forebrain GABAergic system that may be implicated in the changes in stress sensitivity and emotionality observed in exercising subjects.

Physical (in)activity-dependent alterations at the rostral ventrolateral medulla: influence on sympathetic nervous system regulation

A sedentary lifestyle is a major risk factor for cardiovascular disease, and rates of inactivity and cardiovascular disease are highly prevalent in our society. Cardiovascular disease is often associated with overactivity of the sympathetic nervous system, which has both direct and indirect effects on multiple organ systems. Although it has been known for some time that exercise positively affects the brain in terms of memory and cognition, only recently have changes in how the brain regulates the cardiovascular system been examined in terms of physical activity and inactivity. This brief review will discuss the evidence for physical activity-dependent neuroplasticity related to control of sympathetic outflow. It will focus particularly on recent studies from our laboratory and others that have examined changes that occur in the rostral ventrolateral medulla (RVLM), considered one of the primary brain regions involved in the regulation and generation of sympathetic nervous system activity.

The Influence of Exercise on Metabolic Syndrome in Youth: A Review

The metabolic syndrome (MetS) is a clustering of dyslipidemia, hypertension, glucose intolerance, and central obesity or waist circumference that places individuals at high risk for developing cardiovascular or heart disease. Although first characterized in adults, it has been found in children, but the definition of MetS in children is still controversial. Although MetS is most closely associated with obesity in children, 2 factors believed to affect MetS are physical activity (PA) and aerobic power or fitness. Studies using accelerometry to estimate PA of children have shown that low levels are associated with increased risk of developing MetS. Conversely, high levels of PA at moderate to vigorous intensities reduce the risk. Similarly, low levels of aerobic fitness increase the likelihood of developing MetS. These effects appear to be independent of obesity. Studies have also shown that interventions that increase PA levels and improve aerobic fitness cause a reduction in MetS risk; however, an exact prescription for exercise cannot be presently provided. This review provides an in-depth analysis of what is presently known about the relationship between MetS and PA and aerobic fitness in children. In addition, information is presented regarding potential mechanisms for exercise to affect the major markers of MetS.

Recent findings on the organization of central nervous system structures involved in the innervation of endocrine glands and other organs; observations obtained by the transneuronal viral double-labeling technique

This review summarizes the data obtained with the aid of the recently introduced dual viral tracing technique, which uses isogenic recombinants of pseudorabies virus that express unique reporter gene. This approach made possible to explore simultaneously neural circuits of two organs. The results of these studies indicate: (1) there are neurons innervating exclusively a given organ; (2) left-sided predominance in the supraspinal innervation of the endocrine glands (adrenal, ovary) studied, so far; (3) viral co-infection of neurons, i.e., special neuronal populations coexist in different brain areas that are transsynaptically connected with both paired endocrine and non-endocrine organs, endocrine glands and non-endocrine organs, and organs of bodily systems other than the endocrine one. The number of common neurons seems to be related to the need of coordinating action of different systems. The data on co-infection of neurons suggest that the central nervous system has the capacity to coordinate different organ functions via common brain neurons providing supraspinal innervation of the organs.

Distinct, time-dependent effects of voluntary exercise on circadian and ultradian rhythms and stress responses of free corticosterone in the rat hippocampus

Previous work has shown that allowing rats to voluntarily exercise in a running wheel for 4 wk modifies the hypothalamic-pituitary-adrenal axis and behavioral coping responses to stress. To investigate whether long-term voluntary exercise would also affect the free, biologically active fraction of corticosterone in the brain, we conducted an in vivo microdialysis study in the hippocampus of rats. We monitored both the baseline circadian and ultradian patterns of corticosterone in hippocampus dialysates over the diurnal cycle and the responses to forced swim and novelty stress at different stages of exercise. Exercise for 1 d, 2 d, or 1 wk did not affect baseline circadian and ultradian pulse parameters or stress-induced hippocampal free corticosterone concentrations suggesting that acute or short-term periods of exercise do not affect baseline and stress-induced hormone levels. Baseline hormone parameters in 4 wk exercised rats, however, showed significantly increased pulse amplitudes (+108%) and mean free corticosterone levels (+42%) between 1500 and 2100 h but not between 0900 and 1500 h. Surprisingly, although our previous work showed substantial changes in stress-evoked plasma (total) corticosterone responses in long-term exercised animals, no differences in stress-induced hippocampal free hormone responses could be observed between exercised and sedentary animals. This lack of differences was not caused by compensatory changes in plasma corticosteroid-binding-globulin binding levels in exercising rats. Thus, long-term exercising rats show anticipatory increases in glucocorticoid output before the start of the active phase. These rats also reveal the putative existence of a containment mechanism preventing overexposure of the brain to glucocorticoid hormones.

The effect of aerobic physical training on cardiac autonomic control of rats submitted to ovariectomy

OBJECTIVE

To investigate the effect of aerobic physical training on cardiovascular autonomic control in ovariectomized rats using different approaches.

DESIGN

Female Wistar rats were divided into four groups: sedentary sham rats (group SSR), trained sham rats(group TSR), sedentary ovariectomized rats (group SOR), and trained ovariectomized rats (group TOR). Animals from the trained groups were submitted to a physical training protocol (swimming) for 12 weeks.

RESULTS

Pharmacological evaluation showed that animals from group TSR had an increase in their cardiac vagal tonus compared with the animals from groups SSR and SOR. The analysis of heart rate variability (HRV) showed that groups TSR and SOR had fewer low-frequency oscillations (0.20-0.75 Hz) compared with groups SSR and TOR.When groups TSR and SOR were compared, the former was found to have fewer oscillations. With regard to high frequency oscillations (0.75-2.5 Hz), group SSR had a reduction compared with the other groups, whereas group TSR had the greatest oscillation compared with groups SOR and TOR, with all values expressed in normalized units.Analysis of HRV was performed after pharmacological blockade, and low-frequency oscillations were found to be predominantly sympathetic in sedentary animals, whereas there was no predominance in trained animals.

CONCLUSION

Ovariectomy did not change the tonic autonomic control of the heart and, in addition, reduced the participation of sympathetic component in cardiac modulation. Physical training, on the other hand, increased the participation of parasympathetic modulation on the HRV, including ovariectomized rats.

Exercise improves cognitive responses to psychological stress through enhancement of epigenetic mechanisms and gene expression in the dentate gyrus

Background

We have shown previously that exercise benefits stress resistance and stress coping capabilities. Furthermore, we reported recently that epigenetic changes related to gene transcription are involved in memory formation of stressful events. In view of the enhanced coping capabilities in exercised subjects we investigated epigenetic, gene expression and behavioral changes in 4-weeks voluntarily exercised rats.

Methodology/Principal Findings

Exercised and control rats coped differently when exposed to a novel environment. Whereas the control rats explored the new cage for the complete 30-min period, exercised animals only did so during the first 15 min after which they returned to sleeping or resting behavior. Both groups of animals showed similar behavioral responses in the initial forced swim session. When re-tested 24 h later however the exercised rats showed significantly more immobility behavior and less struggling and swimming. If rats were killed at 2 h after novelty or the initial swim test, i.e. at the peak of histone H3 phospho-acetylation and c-Fos induction, then the exercised rats showed a significantly higher number of dentate granule neurons expressing the histone modifications and immediate-early gene induction.

Conclusions/Significance

Thus, irrespective of the behavioral response in the novel cage or initial forced swim session, the impact of the event at the dentate gyrus level was greater in exercised rats than in control animals. Furthermore, in view of our concept that the neuronal response in the dentate gyrus after forced swimming is involved in memory formation of the stressful event, the observations in exercised rats of enhanced neuronal responses as well as higher immobility responses in the re-test are consistent with the reportedly improved cognitive performance in these animals. Thus, improved stress coping in exercised subjects seems to involve enhanced cognitive capabilities possibly resulting from distinct epigenetic mechanisms in dentate gyrus neurons.

Physical Inactivity in Adult Survivors of Childhood Acute Lymphoblastic Leukemia: A Report from the Childhood Cancer Survivor Study

PURPOSE

To determine if adult survivors of childhood acute lymphoblastic leukemia (ALL) are less active (and more inactive) than the general population and to identify modifying factors.

PATIENTS AND METHODS

Physical activity was assessed by self-report in 2,648 adult survivors of the Childhood Cancer Survivor Study. Participants in the Behavioral Risk Factor Surveillance System (BRFSS) survey administered through the Centers for Disease Control and Prevention (CDC) were used as a comparison group.

RESULTS

Survivors had a mean age of 28.7 years (range, 18.0-44.0 years) and were a mean of 23.1 years from their cancer diagnosis (range, 16.0-33.8 years). In multivariate models, ALL survivors were more likely to not meet CDC recommendations for physical activity [odds ratio (OR), 1.44; 95% confidence interval (95% CI), 1.32-1.57] and more likely to be inactive (OR, 1.74; 95% CI, 1.56-1.94) in comparison with the BRFSS general population. Survivors treated with >20-Gy cranial radiotherapy were at particular risk. Compared with BRFSS participants and adjusted for age, race, and ethnicity, survivors were more likely to not meet CDC recommendations (females: OR, 2.07, 95% CI, 1.67-2.56; males: OR, 1.43, 95% CI, 1.16-1.76) and more likely to be inactive (females: OR, 1.86; 95% CI, 1.50-2.31; males: OR, 1.84; 95% CI, 1.45-2.32).

CONCLUSIONS

Long-term survivors of childhood ALL are less likely to meet physical activity recommendations and more likely to report no leisure-time physical activity in the past month. This level of inactivity likely further increases their risk of cardiovascular disease, osteoporosis, and all-cause mortality.

The effect of repeated physical exercise on hippocampus and brain cortex in stressed rats

Sensitivity of target cells to glucocorticoids is regulated by the expression of intracellular glucocorticoid receptor (GR), which mediates the effects of glucocorticoids. The level of GR and of its nuclear transporter protein 70 (Hsp70) were followed in hippocampus and brain cortex of adult Wistar rat males exposed to acute (immobilization, cold) and chronic (social isolation, isolation, and 15 min daily swimming) stress or their combinations. Changes in plasma levels of adenocorticotropic hormone and corticosterone were also studied. A significant decrease in cytosol GR and Hsp70 was observed after acute stress. Opposite to that, chronic stress led to negligible changes in both cytosol GR and Hsp70 levels. Isolation, as chronic psychosocial stressor, caused reduced responsiveness to novel acute stressors, judged by the cytosol GR and Hsp70 levels. This was not observed if chronic isolation was combined with 15 min daily swimming prior to acute exposure to immobilization. The data suggest that repeated physical exercise may, at least in some cases, diminish detrimental effects of chronic social isolation on limbic-hypothalamic-pituitary-adrenocortical axis, as judged by the levels of GR and Hsp70 in the Wistar rat brain.

Multi-tasking in the spinal cord--do 'sympathetic' interneurones work harder than we give them credit for?

The role of interneurones in the control of sympathetic activity has been somewhat of a mystery since, for many years, it was difficult to target these cells for study. Recently scientists have started to unravel the action potential properties of these neurones, where they receive their inputs from and where they project to. This review looks at the information known to date about sympathetic interneurones. The locations of these neurones and their local axonal ramifications suggest that they play a more widespread function than previously thought. Therefore the data to support such a theory are also examined.

Voluntary exercise impacts on the rat hypothalamic-pituitary-adrenocortical axis mainly at the adrenal level

INTRODUCTION

Evidence is accumulating that the regular performance of exercise is beneficial for stress coping. However, the hypothalamic-pituitary-adrenocortical (HPA) axis of voluntarily exercising rats has never been comprehensively investigated.

METHODS

Therefore, male Sprague-Dawley rats were given access to a running wheel in their home cage for 4 weeks in which they ran 4-7 km per night.

RESULTS

After 4 weeks, the exercising animals showed significantly less body weight gain, less abdominal fat tissue, decreased thymus weight, and increased adrenal weight (relative to body weight). Furthermore, tyrosine hydroxylase (TH) mRNA levels were selectively increased in the right adrenal medulla indicating an increase in sympathoadrenomedullary capacity in exercising rats. No changes were observed in paraventricular corticotropin-releasing hormone (CRH), arginine-vasopressin (AVP) and oxytocin mRNA levels. Mineralocorticoid receptor (MR) mRNA levels in hippocampus and glucocorticoid receptor (GR) mRNA levels in frontal cortex, parvocellular paraventricular nucleus and anterior pituitary were unchanged, whereas GR mRNA levels were increased in distinct hippocampal cell layers. Early morning baseline levels of plasma ACTH and corticosterone were similar in both groups. Interestingly, the response to different stressful stimuli (e.g. forced swimming, novelty) revealed that the exercising rats showed stressor-specific changes in HPA hormone responses. Forced swimming evoked a markedly enhanced response in corticosterone levels in the exercising rats. In contrast, if rats were exposed to a novel environment, exercising rats showed a much lower response in corticosterone than the control animals. However, the response in ACTH to either stressor was comparable between groups. Thus, in exercising rats physically demanding stressors evoke enhanced glucocorticoid responses whereas mild psychologically stressful stimuli such as novelty result in an attenuated glucocorticoid response. Interestingly, this attenuated hormone response corresponded with the observation that the exercising rats showed less anxious behaviour in the novelty situation.

CONCLUSIONS

The differential responses in plasma corticosterone levels to different types of stress in the face of comparable responses in ACTH levels underscore the existence of critical regulatory control mechanisms at the level of the adrenal gland. We have hypothesized that changes in the sympathoadrenomedullary input may play an important role in these distinct glucocorticoid responses to stress. Our previous studies have shown similar changes in voluntarily exercising mice. Therefore, we conclude that the effects of exercise on the organism are not species-specific. Thus, our observations may have translational implications for the human situation.

Long-term voluntary exercise and the mouse hypothalamic-pituitary-adrenocortical axis: impact of concurrent treatment with the antidepressant drug tianeptine

We investigated whether voluntary exercise and concurrent antidepressant treatment (tianeptine; 20 mg/kg/day; 4 weeks) exert synergistic effects on the mouse hypothalamic-pituitary-adrenocortical (HPA) axis. Animals had access to a running wheel, were treated with the antidepressant, or received both conditions combined. Control mice received no running wheel and no drug treatment. Exercise resulted in asymmetric changes in the adrenal glands. Whereas sedentary mice had larger left adrenals than right ones, this situation was abolished in exercising animals, mainly due to enlargement of the right adrenal cortex. However, antidepressant treatment alone was ineffective whereas the combination of antidepressant treatment and exercise resulted in an enlargement of both adrenal cortices. In these respective conditions, the levels of tyrosine hydroxylase (TH) mRNA expression in the left and right adrenal medullas varied greatly in parallel to the changes observed in the adrenal cortex sizes. TH mRNA expression in the locus coeruleus of exercising mice was significantly increased irrespective of concomitant tianeptine treatment. Corticotrophin-releasing factor mRNA levels in the hypothalamic paraventricular nucleus were decreased after voluntary exercise but were unaffected by tianeptine. Exercise, particularly in combination with tianeptine treatment, resulted in decreased early morning baseline plasma levels of corticosterone. If animals were exposed to novelty (i.e. a mild psychological stressor), a decreased response in plasma corticosterone levels was observed in the exercising mice. By contrast, after restraint, a mixed physical and psychological stressor, exercising mice showed an enhanced response in plasma corticosterone compared to the controls; a response which was even further boosted in exercising mice concomitantly treated with tianeptine. Under either condition, plasma adrenocorticotrophic hormone levels were not different between groups. Thus, voluntary exercise impacts substantially on HPA axis regulation. Concurrent tianeptine treatment results in synergistic actions, mainly at the adrenal level, affecting both its structure and function.

Oxytocin levels in the posterior pituitary and in the heart are modified by voluntary wheel running

We hypothesized that voluntary wheel running results in increased secretion of oxytocin, a peptide involved in the stress response. An additional hypothesis was that prolonged exercise affects oxytocin levels in the heart, which is in line with the potential role of oxytocin in cardiovascular functions. Voluntary wheel running lasted 3 weeks and daily running distances increased progressively reaching maximum levels about 8 km (Sprague-Dawley rats) and 4 km (Lewis strain). The exercise resulted in significant reduction of epididymal fat, slight increase in glucose transporter GLUT4 mRNA levels and significant enhancement of plasma density. Voluntary exercise failed to influence plasma oxytocin levels either in Lewis or Sprague-Dawley rats, but it resulted in a significant decrease of oxytocin concentrations in the posterior pituitary. Plasma oxytocin concentrations were not modified even if the measurements were made in the dark phase of the day. In voluntary wheel running Sprague-Dawley rats, the content of oxytocin in the right heart atrium was lower than in controls. Thus, the present findings demonstrate that prolonged voluntary wheel running results in a decrease in pituitary oxytocin content without evident changes in hormone concentrations in peripheral blood. However, prolonged exercise used has a significant impact on oxytocin levels in the heart.

Effect of exercise on ovarian morphology and expression of nerve growth factor and alpha(1)- and beta(2)-adrenergic receptors in rats with steroid-induced polycystic ovaries

Oestadiol valerate (EV)-induced polycystic ovaries (PCO) in rats cause anovulation and cystic ovarian morphology. Denervation of ovarian sympathetic nerves restores ovulatory disruption. In the present study, we determined whether 5 weeks of voluntary exercise influence ovarian morphology and the expression of sympathetic markers in the EV-induced PCO rat model. The effect of exercise on (i) ovarian morphology; (ii) mRNA and protein expression of nerve growth factor (NGF); and (iii) mRNA and number of ovarian-expressing cells for the NGF receptor (p75 neurotrophin receptor) and the alpha(1a)-, alpha(1b)-, alpha(1d)- and beta(2)-adrenergic receptors (ARs) in rats with EV-induced PCO was evaluated. PCO was induced by a single i.m. injection of EV, and controls were injected with oil alone in adult cycling rats. The rats were divided into four groups: (i) control (oil); (ii) exercise group (oil + exercise); (iii) a PCO group (EV); and (iv) a PCO exercise group (EV + exercise). The exercise and PCO exercise groups ran voluntarily for 5 weeks in computer-monitored wheels placed in the cages where they were housed. The results obtained indicated that ovarian morphology was almost normalised in the PCO exercise group; NGF mRNA and protein concentrations were normalised in the PCO exercise group; high numbers of NGF receptor expressing cells in PCO ovaries were lowered by exercise; and the number of immunopositive cells of the different AR subtypes were all reduced after exercise in the PCO group, except for the alpha(1b)- and beta(2)-AR whereas the mRNA levels were unaffected, indicating transcriptional regulation. In conclusion, our data indicate a beneficial effect of regular exercise, as a modulator of ovarian sympathetic innervation, in the prevention and treatment of human PCOS.

Putative role of the NTS in alterations in neural control of the circulation following exercise training in rats

Exercise training (ExTr) has been associated with alterations in neural control of the circulation, including effects on arterial baroreflex function. The nucleus tractus solitarius (NTS) is the primary termination site of cardiovascular afferents and critical in the regulation of baroreflex-mediated changes in heart rate (HR) and sympathetic nervous system outflow. The purpose of the present study was to determine whether ExTr is associated with alterations in neurotransmitter regulation of neurons involved in control of cardiovascular function at the level of the NTS. We hypothesized that ExTr would increase glutamatergic and reduce GABAergic transmission in the NTS and that, collectively, these changes would result in a greater overall sympathoinhibitory drive from the NTS in ExTr animals. To test these hypotheses, male Sprague-Dawley rats were treadmill trained or maintained under sedentary conditions for 8-10 wk. NTS microinjections were performed in Inactin-anesthetized animals instrumented to record mean arterial pressure (MAP), HR, and lumbar sympathetic nerve activity (LSNA). Generalized activation of the NTS with unilateral microinjections of glutamate (1-10 mM, 30 nl) produced dose-dependent decreases in MAP, HR, and LSNA that were unaffected by ExTr. Bilateral inhibition of NTS with the GABAA agonist muscimol (1 mM, 90 nl) produced increases in MAP and LSNA that were blunted by ExTr. In contrast, pressor and sympathoexcitatory responses to bilateral microinjections of the ionotropic glutamate receptor antagonist, kynurenate (40 mM, 90 nl), were similar between groups. Bradycardic responses to bilateral microinjections of the GABAA antagonist bicuculline (0.1 mM, 90 nl) were attenuated by ExTr. These data indicate that alterations in neurotransmission at the level of the NTS contribute importantly to regulation of HR and LSNA in ExTr animals. In addition to alterations at NTS, these experiments suggest indirectly that changes in other cardiovascular nuclei contribute to the observed alterations in neural control of the circulation following ExTr.

Neuroplastic adaptations to exercise: neuronal remodeling in cardiorespiratory and locomotor areas

Neuronal activity has been shown to be attenuated in cardiorespiratory and locomotor centers of the brain in response to a single bout of exercise in trained (TR) vs. untrained (UN) animals, but the mechanisms remain obscure. Based on this finding, dendritic branching patterns of seven brain areas associated with cardiorespiratory and locomotor activity were examined in TR and UN animals. Twenty-eight male Sprague-Dawley rats were kept in individual cages and divided into TR and UN. TR were provided with a running wheel and exercised spontaneously. After 85 or 120 days, exercise training indexes were obtained, including maximal oxygen consumption, percent body fat, resting heart rate, and heart weight-to-body weight ratios. The brain was removed and processed according to a modified Golgi-Cox procedure. Impregnated neurons from seven brain areas were examined in coronal sections: the periaqueductal gray, posterior hypothalamic area, nucleus of the tractus solitarius, rostral ventrolateral medulla, cuneiform nucleus, nucleus cuneatus, and cerebral cortex. Neurons were traced using a camera lucida technique and analyzed using the Sholl analysis of dendritic branching. t-tests were conducted to compare the mean number of intersections per neuron by grouping inner rings and outer rings and also comparing the total number of intersections per animal. There were significant differences between groups in the posterior hypothalamic area, periaqueductal gray, cuneiform nucleus, and nucleus of the tractus solitarius in the inner rings, outer rings, and the total number of intersections per animal. Our results show that dendritic fields of neurons in important cardiorespiratory and locomotor centers of the brain are attenuated in TR animals.

Effect of the activation of central 5-HT2C receptors by the 5-HT2C agonist mCPP on blood pressure and heart rate in rats

In the present study we investigated the role of central 5-HT2C receptors in the control of blood pressure and heart rate in non-stressed and stressed, adult, male, Wistar rats. Third ventricle injections of the 5-HT2C agonist mCPP elicited a significant increase in blood pressure in non-stressed animals. The initial period of this hypertensive response (10-30 min after mCPP administration) was accompanied by baroreflex-mediated bradycardia, while after this period the coexistence of hypertension and tachycardia was observed. These cardiovascular effects promoted by the central administration of mCPP were blocked by pretreatment with the 5-HT2C antagonist, SDZ SER 082. The administration of SDZ SER 082 alone induced no significant changes in blood pressure or heart rate. The pharmacological stimulation of central 5-HT2C receptors by mCPP did not change the hypertensive or tachycardic responses induced by restraint stress. Conversely, the blockade of central 5-HT2C receptors by SDZ SER 082 blunted stress-induced hypertension without modifying stress-induced tachycardia. It is concluded that the activation of central 5-HT2C receptors induces hypertension in non-stressed rats and that the normal function of these receptors is essential for the rise in blood pressure that occurs in the course of restraint stress.

Cardiac autonomic activity and Type II diabetes mellitus

CAN (cardiac autonomic neuropathy) is a common complication of diabetes. Meta-analyses of published data demonstrate that reduced cardiovascular autonomic function, as measured by heart rate variability, is strongly associated with an increased risk of silent myocardial ischaemia and mortality. A major problem in ischaemia-induced impairment of vascular performance in the diabetic heart is unrecognized cardiac sympathetic dysfunction. Determining the presence of CAN is based on a battery of autonomic function tests and techniques such as SPECT (single-photon emission computed tomography) and PET (positron emission tomography). Nevertheless, spectral analysis of heart rate variability seems to remain the primary technique in evaluating CAN, due to its low cost, easy use and good intra-individual reproducibility.

Physical exercise decreases neuronal activity in the posterior hypothalamic area of spontaneously hypertensive rats

Recently, physical exercise has been shown to significantly alter neurochemistry and neuronal function and to increase neurogenesis in discrete brain regions. Although we have documented that physical exercise leads to molecular changes in the posterior hypothalamic area (PHA), the impact on neuronal activity is unknown. The purpose of the present study was to determine whether neuronal activity in the PHA is altered by physical exercise. Spontaneously hypertensive rats (SHR) were allowed free access to running wheels for a period of 10 wk (exercised group) or no wheel access at all (nonexercised group). Single-unit extracellular recordings were made in anesthetized in vivo whole animal preparations or in vitro brain slice preparations. The spontaneous firing rates of PHA neurons in exercised SHR in vivo were significantly lower (8.5 ± 1.6 Hz, n = 31 neurons) compared with that of nonexercised SHR in vivo (13.7 ± 1.8 Hz, n = 38 neurons; P < 0.05). In addition, PHA neurons that possessed a cardiac-related rhythm in exercised SHR fired significantly lower (6.0 ± 1.8 Hz, n = 11 neurons) compared with nonexercised SHR (12.1 ± 2.4 Hz, n = 18 neurons; P < 0.05). Similarly, the spontaneous in vitro firing rates of PHA neurons from exercised SHR were significantly lower (3.5 ± 0.3 Hz, n = 67 neurons) compared with those of nonexercised SHR (5.6 ± 0.5 Hz, n = 58 neurons; P < 0.001). Both the in vivo and in vitro findings support the hypothesis that physical exercise can lower spontaneous activity of neurons in a cardiovascular regulatory region of the brain. Thus physical exercise may alter central neural control of cardiovascular function by inducing lasting changes in neuronal activity.

Role of central 5-HT3 receptors in the control of blood pressure in stressed and non-stressed rats

The aim of the present study was to investigate the participation of central 5-HT(3) receptors in the control of blood pressure and heart rate (HR) of non-stressed and stressed rats. The pharmacological stimulation of brain 5-HT(3) receptors by third ventricle injections of the selective 5-HT(3) receptor agonist m-CPBG induced a significant decrease in blood pressure in non-stressed rats and impaired the hypertensive response induced by restraint stress. The blockade of brain 5-HT(3) receptors by the central administration of the selective 5-HT(3) antagonist ondansetron elicited a significant increase in blood pressure in non-stressed rats. Conversely, the hypertensive response induced by restraint stress was not affected by central administration of ondansetron. Additionally, baroreflex-mediated bradycardia during phenylephrine-induced hypertensive response was preserved in non-stressed animals receiving third ventricle injections of m-CPBG, while the baroreflex-mediated tachycardia that occurs during the hypotensive response induced by the administration of sodium nitroprusside was impaired. It is concluded that the serotoninergic component represented by the brain 5-HT(3) receptors exerts a tonic inhibitory influence on the central control of blood pressure in non-stressed rats, probably by a sympathoinhibitory-related mechanism. On the other hand, during stress, this central 5-HT(3)-dependent inhibitory drive is overwhelmed by the different neurochemical systems that harmonically trigger and sustain the hypertensive response.

Regular voluntary exercise reduces anxiety-related behaviour and impulsiveness in mice

We embarked on a study to delineate the behavioural changes in mice after 4 weeks of voluntary exercise. As an initial behavioural characterization, we exposed the control and exercising mice to a modified hole board and an open field test. As compared to control mice, exercising animals showed clear signs of increased behavioural inhibition (e.g. a longer latency to enter unprotected areas), suggesting increased anxiety in these animals. In addition, the exercising mice were reluctant to spend time in the open field's centre during the beginning of the 30-min open field test, but compensated for this at later times. Paradoxically, the exercising animals showed more rearings on the board of the modified hole board, indicating decreased anxiety. Thus, the behavioural inhibition seen in exercising mice is likely to represent decreased stress responsiveness at the behavioural level which can also be interpreted as reduced impulsiveness. To clarify whether voluntary exercise evolves in more or less anxiety-related behaviour, we exposed animals to the elevated plus-maze and the dark-light box, two selective tests for unconditioned anxiety. Clearly, compared to the control animals, exercising mice spent significantly more time on the open arm of the plus-maze and spent double the amount of time in the light compartment of the dark-light box. Taken together, we conclude that long-term voluntary exercise appears to result in decreased anxiety-related behaviour and impulsiveness. Thus, our observations fit into the concept that regular exercise strengthens endogenous stress coping mechanisms, thereby protecting the organism against the deleterious effects of stress.

Blood-brain barrier disruption in the hypothalamus of young adult spontaneously hypertensive rats

Vascular permeability and endothelial glycocalyx were examined in young adult spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP), and Wistar Kyoto rats (WKY) as a control, in order to determine earlier changes in the blood-brain barrier (BBB) in the hypothalamus in chronic hypertension. These rats were injected with horseradish peroxidase (HRP) as an indicator of vascular permeability. Brain slices were developed with a chromogen and further examined with cationized ferritin, a marker for evaluating glycocalyx. Staining for HRP was seen around vessels in the hypothalamus of SHR and SHRSP, but was scarce in WKY. The reaction product of HRP appeared in the abluminal pits of endothelial cells and within the basal lamina of arterioles, showing increased vascular permeability in the hypothalamus of SHR and SHRSP, whereas there were no leaky vessels in the frontal cortex of SHR and SHRSP, or in both areas of WKY. The number of cationized ferritin particles binding to the capillary endothelial cells was decreased in the hypothalamus of SHR and SHRSP, while the number decreased in the frontal cortex of SHRSP, compared with those in WKY. Cationized ferritin binding was preserved in some leaky arterioles, while it was scarce or disappeared in other leaky vessels. These findings suggest that BBB disruption occurs in the hypothalamus of 3-month-old SHR and SHRSP, and that endothelial glycocalyx is markedly damaged there without a close relationship to the early changes in the BBB.

Differential blood pressure and heart rate responses to supramedullary brain stimulation in cats

The purpose of this study was to compare the cardiovascular responses to electrical stimulation of different supramedullary brain regions. Arterial blood pressure (BP) and heart rate (HR) effects were elicited by electrical stimulation of the lateral hypothalamus (LH), mamillary bodies (Mm), substantia nigra (SN), globus pallidus (GP), and the subthalamic nucleus (Sub) in conscious, freely moving cats. Pressor responses were obtained from all of these regions. The higher intensity of stimulation the higher increase in BP and HR was obtained. However, clear-cut differences occurred in the effects both during and after the termination of stimulations. Namely, a continuous increase in BP and HR was obtained from the LH and SN. In contrast, the initial increase in BP and HR was followed by a reduction compared to the peak value of the effects of stimulation in the GP and the Sub. However, the BP and HR never reduced to the pre-stimulaion level during the stimulation. Also the changes following the cessation of stimulation at the different brain loci were dissimilar. The BP and HR either returned gradually to the pre-stimulation level, or long-lasting oscillation occurred. The electrical activity of the nucleus of the solitary tract (NTS) and the vagus nerve co-varied with the changes in BP and HR. It is concluded that the supramedullary stimulations produce differential cardiovascular effects, and these effects are modified by the baroreflexes that are activated by the electrically elicited rise in blood pressure.

Single CNS neurons link both central motor and cardiosympathetic systems: a double-virus tracing study

Two anatomical experiments were performed to test the hypothesis that single CNS neurons link the central areas that regulate the somatomotor and sympathetic systems. First, the retrograde neuronal tracer cholera toxin beta-subunit was injected into the lateral parafascicular thalamic nucleus, a region that projects to both the motor cortex and striatum. Several days later, a second injection of the retrograde transneuronal tracer, pseudorabies virus (PRV), was made in the same rats in the stellate ganglion, which provides the main sympathetic supply to the heart. Using immunohistochemical methods, we demonstrate that the cholinergic neurons of the pedunculopontine tegmental nucleus (PPN) are connected to both systems. The second experiment used two isogenic strains of Bartha PRV as double transneuronal tracers. One virus contained the unique gene for green fluorescent protein (GFP) and the other had the unique gene for beta-galactosidase (beta-gal). GFP-PRV was injected in the stellate ganglion and beta-gal-PRV was injected into the primary motor cortex. Double-labeled neurons were found in the lateral hypothalamic area (50% contained orexin) and PPN (approximately 95% were cholinergic). Other double-labeled neurons were identified in the deep temporal lobe (viz., amygdalohippocampal zone and lateral entorhinal cortex), posterior hypothalamus, ventral tuberomammillary nucleus, locus coeruleus, laterodorsal tegmental nucleus, periaqueductal gray matter, dorsal raphe nucleus, and nucleus tractus solitarius. These results suggest these putative command neurons integrate the somatomotor and cardiosympathetic functions and may affect different behaviors (viz., arousal, sleep, and/or locomotion).

Influence of regular voluntary exercise on spontaneous and social stress-affected sleep in mice

To investigate the impact of regular physical exercise on sleep, we assessed sleep-wake behaviour in male C57BL/6N mice with and without long-term access (i.e. 4 weeks) to a running wheel. We studied sleep-wake behaviour during undisturbed conditions as well as after social stress. The exercising mice ran approximately 4 km/day, which affected their physical constitution, their spontaneous sleep-wake pattern and their endocrine and sleep responses to stress. When compared with the control mice, exercising animals had more muscle substance, less body fat and heavier adrenal glands. At baseline, exercising mice showed fewer, but longer-lasting, sleep episodes (indicating improved sleep consolidation) and less rapid-eye-movement sleep. In both control and exercising mice, mild social stress (elicited by a 15-min social conflict) evoked elevated plasma levels of adrenocorticotrophic hormone and corticosterone, an increase in non-rapid-eye-movement sleep, an enhancement of low-frequency activity in the electroencephalogram within non-rapid-eye-movement sleep (indicating increased sleep intensity) and a decrease in wakefulness. However, as compared with the control animals, exercising mice responded to social stress with higher corticosterone levels, but not adrenocorticotrophic hormone levels, suggesting an increased sensitivity of their adrenal glands to adrenocorticotrophic hormone. Moreover, in control mice, social stress increased rapid-eye-movement sleep in parallel to non-rapid-eye-movement sleep, whereas this stressor selectively decreased rapid-eye-movement sleep in exercising animals. Corticosterone is known to decrease rapid-eye-movement sleep. Therefore, changes in the regulation of the hypothalamic-pituitary-adrenocortical axis as a result of the long-term exercise may contribute to the observed differences in spontaneous and social stress-affected sleep. In conclusion, regular exercise appears to increase sleep quality and reverses the effects of mild social stress on rapid-eye-movement sleep.

Daily exercise normalizes the number of diaphorase (NOS) positive neurons in the hypothalamus of hypertensive rats

It is well known that nitric oxide (NO), within the paraventricular nucleus (PVN) of the hypothalamus, mediates sympatho-inhibition via an inhibitory GABA-ergic mechanism. Furthermore, the inhibitory GABA-ergic mechanism is impaired in the spontaneously hypertensive rat (SHR). These data suggest that the NO system, within the PVN, may also be impaired in the SHR. In addition, previous studies have documented that daily exercise attenuates the development of tachycardia, hypertension and blood pressure related cardiovascular disease risk factors in SHR. These data suggest that daily exercise enhances the inhibitory GABA-ergic and/or NO systems. Therefore, this study was designed to test the hypothesis that hypertension, in the SHR, is associated with a lower number of NADPH-diaphorase (a commonly used marker for neuronal NOS activity) positive neurons within the PVN and that daily exercise increases the number of NOS positive neurons. Using a standard histochemical protocol, NOS positive neurons were measured in the PVN, supraoptic nucleus, median preoptic area, lateral hypothalamus, nucleus of the tractus solitarius and rostral ventrolateral medulla. Results document that SHR have significantly fewer NOS-positive neurons in the PVN than their genetic control, the Wistar-Kyoto (WKY) rats (110+/-11 versus 139+/-17). Furthermore, daily exercise increased the number of NOS positive neurons in the SHR to levels seen in the WKY rats. These data demonstrate that hypertension, in the SHR, is associated with a lower number of NOS positive neurons within the PVN and that daily exercise increases the number of NOS positive neurons within the PVN.