CHF Rats Research Articles

An animal model of trait anxiety: Carioca high freezing rats as a model of generalized anxiety disorder.

Despite being one of the main components of anxiety and playing a pivotal role in how an individual perceives and copes with anxiogenic situations or responds to a given treatment, trait anxiety is paradoxically omitted in most animal models of anxiety. This is problematic and particularly more concerning in models that are used to screen drugs and other treatments for specific anxiety disorders and to investigate their neurobiological mechanisms. Our group has been engaged in the search for specific anxiety-related traits in animal models of anxiety. We developed two new lines of rats with strong phenotypic divergence for high (Carioca High-conditioned Freezing [CHF]) and low (Carioca Low-conditioned Freezing [CLF]) trait anxiety as expressed in the contextual fear conditioning paradigm. Here, we summarize key behavioral, pharmacological, physiological, and neurobiological differences in one these lines, the CHF rat line, relative to randomized-cross controls and discuss how far they represent a valid and reliable animal model of generalized anxiety disorder and so high trait anxiety.

Increased hippocampal CREB phosphorylation after retrieval of remote contextual fear memories in Carioca high-conditioned freezing rats

The participation of the hippocampal formation in consolidation and reconsolidation of contextual fear memories has been widely recognized and known to be dependent on the activation of the cAMP response element (CRE) binding protein (CREB) pathway. Recent findings have challenged the prevailing view that over time contextual fear memories migrate to neocortical circuits and no longer require the hippocampus for retrieval of remote fearful memories. It has also recently been found that this brain structure is important for the maintenance and recall of remote fear memories associated with aversive events, a common trait in stress-related disorders such as generalized anxiety disorder (GAD), major depression, and post-traumatic stress disorder. In view of these findings, here we examined the putative role of CREB in the hippocampus of an animal model of GAD during the retrieval of remote contextual fear memories. Specifically, we evaluated CREB phosphorylation in the hippocampus of male Carioca High- and Low-conditioned Freezing rats (CHF and CLF, respectively) upon re-exposure of animals to contextual cues associated to footshocks weeks after fear conditioning. Age-matched male rats from a randomized crossbreeding population served as controls (CTL). Adrenal catecholamine levels were also measured as a biological marker of stress response. Seven weeks after contextual fear conditioning, half of the sample of CHF (n = 9), CLF (n = 10) and CTL (n = 10) rats were randomly assigned to return to the same context chamber where footshocks were previously administrated (Context condition), while the remaining animals were individually placed in standard housing cages (Control condition). Western blot results indicated that pCREB levels were significantly increased in the hippocampus of CHF rats for both Context and Control conditions when compared to the other experimental groups. CHF rats in the Context condition also exhibited significant more freezing than that observed for both CLF and CTL rats. Lastly, CHF animals in the Context condition displayed significantly higher adrenal catecholamine levels than those in the Control condition, whereas no differences in catecholamine levels were observed between Context and Control conditions for CLF and CTL rats. These findings are discussed from a perspective in which the hippocampus plays a role in the maintenance and recall of remote contextual fear memories via the CREB pathway.

Glycyrrhiza uralensis promote the metabolism of toxic components of Aconitum carmichaeli by CYP3A and alleviate the development of chronic heart failure.

Aconitum, as "the first drug of choice for invigorating Yang and saving lives", has been widely used for the treatment of heart failure. However, toxic components of Aconitum can easily lead to serious arrhythmia, even death (Y. CT., 2009; Zhang XM., 2018). In this study, a High Performance Liquid Chromatography (HPLC) method for the determination of aconitine (AC), mesaconitine (MA) and hypaconitine (HA) was established; The effect of Glycyrrhiza on CYP3A1 / 2 mRNA expression was detected by RT-PCR; SD rats were given Aconitum and compatibility of Glycyrrhizae and Aconitum by gavage respectively, the blood concentration of toxic components were determined by LC-MS / MS; The CHF rat model was established by intraperitoneal injection of adriamycin (2.5 mg / kg), and were randomly divided into model, Aconitum, the compatibility of Glycyrrhizae and Aconitum and Captopril group, 5 mice/group. After 4 weeks of gavage, the corresponding indexes were detected by ELISA and HPLC. The results showed that Ketoconazole significantly inhibited the metabolites of AC, MA and HA; Glycyrrhiza induced CYP3A gene expression; The level of ALD in the compatibility of Glycyrrhizae and Aconitum group was significantly lower than that in Aconitum group. After intervention with the compatibility of Glycyrrhizae and Aconitum, ATP increased, ADP decreased significantly. In conclusion, we found Glycyrrhiza promoted the metabolism of toxic components of Aconitum by up regulating the expression of CYP3A, and reduced the content of BNP, Ang II and ALD, improved the energy metabolism disorder of myocardium, alleviated the development of CHF.

High-sugar/high-fat diet modulates the effects of chronic stress in cariocas high- and low-conditioned freezing rats

Stress and eating disorders are closely related and are a topic of major concern due to their burden on human health. Engaging in unhealthy eating habits may come as a result of stress, and it often serves to alleviate the symptoms of anxiety or as a distraction from the stressor itself or self-awareness. However, it can also lead to negative feelings of a person's body figure, guilty, or shame. As diverse as these consequences are in humans, so are the effects of the combined administration of stress and hypercaloric food in animals’ models. In this study, we assessed the influence of individual innate behavioral predisposition on the effects of chronic unpredictable mild stress and the dietary supplementation with high-sugar/high-fat food. These conditions were applied to male Carioca low- and high-conditioned freezing (CLF and CHF) rats for 21 days. Behavioral results show that the hypercaloric supplement had a protective effect over the alterations caused by the stress. Notably, it was more strongly observed in CHF rather than CLF animals. As the chronic stress led to an impaired behavior in the contextual fear conditioning and the forced swimming tests in the CLF line, animals fed with the HSHF pellet scored responses similar to their untreated control. On CHF rats, these effects also were seen to a broader extent on the open field test, where the locomotor behavior was also increased. No major effects of the diet were seen in the unstressed groups. Overall, our results show that the influences of both chronic stress and hypercaloric feeding depend on innate differences in fear response traits of male Carioca rats.

Effects of enriched-potassium diet on cardiorespiratory outcomes in experimental non-ischemic chronic heart failure

BackgroundChronic heart failure (CHF) is a global health problem. Increased sympathetic outflow, cardiac arrhythmogenesis and irregular breathing patterns have all been associated with poor outcomes in CHF. Several studies showed that activation of the renin-angiotensin system (RAS) play a key role in CHF pathophysiology. Interestingly, potassium (K+) supplemented diets showed promising results in normalizing RAS axis and autonomic dysfunction in vascular diseases, lowering cardiovascular risk. Whether subtle increases in dietary K+ consumption may exert similar effects in CHF has not been previously tested. Accordingly, we aimed to evaluate the effects of dietary K+ supplementation on cardiorespiratory alterations in rats with CHF.MethodsAdult male Sprague–Dawley rats underwent volume overload to induce non-ischemic CHF. Animals were randomly allocated to normal chow diet (CHF group) or supplemented K+ diet (CHF+K+ group) for 6 weeks. Cardiac arrhythmogenesis, sympathetic outflow, baroreflex sensitivity, breathing disorders, chemoreflex function, respiratory–cardiovascular coupling and cardiac function were evaluated.ResultsCompared to normal chow diet, K+ supplemented diet in CHF significantly reduced arrhythmia incidence (67.8 ± 15.1 vs. 31.0 ± 3.7 events/hour, CHF vs. CHF+K+), decreased cardiac sympathetic tone (ΔHR to propranolol: − 97.4 ± 9.4 vs. − 60.8 ± 8.3 bpm, CHF vs. CHF+K+), restored baroreflex function and attenuated irregular breathing patterns. Additionally, supplementation of the diet with K+ restores normal central respiratory chemoreflex drive and abrogates pathological cardio-respiratory coupling in CHF rats being the outcome an improved cardiac function.ConclusionOur findings support that dietary K+ supplementation in non-ischemic CHF alleviate cardiorespiratory dysfunction.

Acquisition and extinction of contextual fear conditioning in Carioca high- and low-conditioned freezing rats

Carioca High- and Low-conditioned Freezing (CHF and CLF, respectively) rats are two bidirectional breeding lines of animals with high and low levels of defensive conditioned freezing response to contextual cues that are associated with an aversive stimulus. In the last decade, various studies have investigated their physiology and response to other external stimuli as a model of trait anxiety. However, the process of the extinction of their characteristic freezing response is not well understood. The present study investigated the acquisition and extinction of a contextual fear conditioning protocol among these animals. The results showed that CLF rats were unable to consolidate aversive memories and thus were unresponsive to extinction. In contrast, CHF rats still exhibited a large freezing response to contextual cues and were susceptible to extinction, reaching levels of freezing that were comparable to control, randomly bred animals. These findings contribute to validating CHF rats as a model of trait anxiety and their usefulness for evaluating exposure protocols to ameliorate excessive levels of context-conditioned fear.

Behavioral effects of chronic stress in Carioca High- and Low-Conditioned Freezing rats

Chronic unpredictable mild stress (CUMS) is a widely used model to study stress-coping strategies in rodents. Different factors have been shown to influence whether animals adopt passive or active coping responses to CUMS. Individual adaptation and susceptibility to the environment seem to play a critical role in this process. To further investigate this relationship, we examined the effects of CUMS on Carioca high- and low-conditioned freezing rats (CHF and CLF, respectively), bidirectional lines of animals selected for high and low freezing in response to contextual cues that were previously associated with footshocks. For this purpose, the behavior of CHF and CLF animals was evaluated in the contextual fear conditioning, open field, elevated T maze, and forced swimming tests before and after 21 days of CUMS. Animals kept under standard housing conditions were used as controls. For all tests, CHF rats were more susceptible to the effects of CUMS compared to CLF and control groups. CHF animals exposed to CUMS displayed a reduction in freezing behavior, decreased number of entries and time spent in the center of the open field, greater latencies to become immobile, and increased avoidance and escaping behaviors in the elevated T maze. Overall, these findings support the hypothesis that a heightened susceptibility to the environment exerts a strong influence on coping responses to chronic stress.

Alcohol intake in Carioca High- and Low-conditioned Freezing rats

Evidence from clinical and epidemiological studies point towards an association between generalized anxiety disorder (GAD) and alcohol abuse. In the present study we investigated whether a similar relationship could be observed in an animal model of GAD. Specifically, we evaluated the alcohol intake of Carioca High- and Low-conditioned Freezing rats (CHF and CLF, respectively). Sex differences in alcohol drinking behavior were also studied. Male and female rats from randomized crossbreeding populations served as controls (CTL). Free- and forced-choice protocols were used to measure alcohol consumption, and quinine and saccharin were used as taste control solutions. Our results indicate that CHF rats consumed more alcohol than CLF and CTL ones in both the free-choice (6 and 10% concentrations) and the forced-choice (10% concentration) conditions. CHF female rats exhibited the highest amount of alcohol intake in the forced-choice condition. CHF females also consumed more quinine than CHF male rats. Finally, CHF rats exhibited lower saccharin consumption compared to CLF and CTL animals. Altogether, these results support the hypothesis that there is a positive relationship between anxiety and alcohol intake, and provide further evidence for the use of CHF rats as a model of GAD.

Distinct patterns of brain Fos expression in Carioca High- and Low-conditioned Freezing Rats.

The bidirectional selection of high and low anxiety-like behavior is a valuable tool for understanding the neurocircuits that are responsible for anxiety disorders. Our group developed two breeding lines of rats, known as Carioca High- and Low-conditioned Freezing (CHF and CLF), based on defensive freezing in the contextual fear conditioning paradigm. A random selected line was employed as a control (CTL) comparison group for both CHF and CLF lines of animals. The present study performed Fos immunochemistry to investigate changes in neural activity in different brain structures among CHF and CLF rats when they were exposed to contextual cues that were previously associated with footshock. The study indicated that CHF rats expressed high Fos expression in the locus coeruleus, periventricular nucleus of the hypothalamus (PVN), and lateral portion of the septal area and low Fos expression in the medial portion of the septal area, dentate gyrus, and prelimbic cortex (PL) compared to CTL animals. CLF rats exhibited a decrease in Fos expression in the PVN, PL, and basolateral nucleus of the amygdala and increase in the cingulate and perirhinal cortices compared to CTL animals. Both CHF and CLF rats displayed Fos expression changes key regions of the anxiety brain circuitry. The two bidirectional lines exhibit different pattern of neural activation and inhibition with opposing influences on the PVN, the main structure involved in regulating the hypothalamic-pituitary-adrenal neuroendocrine responses observed in anxiety disorders.

Cued Fear Conditioning in Carioca High- and Low-Conditioned Freezing Rats.

Anxiety disorders (AD) comprise a broad range of psychiatric conditions, including general anxiety (GAD) and specific phobias. For the last decades, the use of animal models of anxiety has offered important insights into the understanding of the association between these psychopathologies. Here, we investigate whether Carioca high- and low-conditioned freezing rats (CHF and CLF, respectively), a GAD animal model of anxiety, show similar high- and low-freezing behavioral phenotypes for cued auditory fear conditioning. Adult CHF (n = 16), CLF (n = 16) and normal age-matched Wistar rats (control, CTL, n = 16) were tested in a classical auditory-cued fear conditioning paradigm over 3 days (Tone + Shock and Tone only groups, n = 8 per treatment). Freezing responses were measured and used as evidence of fear conditioning. Overall, both CHF and CLF rats, as well as CTL animals displayed fear conditioning to the auditory CS. However, CLF animals showed a rapid extinction to the auditory conditioned stimulus compared to CHF and CTL rats. We discuss these findings in the context of the behavioral and neuronal differences observed in rodent lines of high and low anxiety traits.

MiR-129-5p improves cardiac function in rats with chronic heart failure through targeting HMGB1.

Increasing evidence shows that miRNAs play pivotal roles in cardiovascular diseases, including heart failure (HF). The aim of this study was to investigate the role of miR-129-5p in chronic heart failure and the underlying mechanisms. The levels of miR-129-5p and HMGB1 in chronic heart failure patients (CHF) and normal controls were examined by RT-qPCR and ELISA. Cardiac function, hemodynamics parameters, oxidative stress, and inflammation factors were analyzed in CHF rat model after transfection of miR-129-5p or HMGB1. Dual-luciferase activity reporter assay was conducted to validate the interaction between miR-129-5p and HMGB1. Downregulation of miR-129-5p and upregulation of HMGB1 were observed in the serum of CHF patients, respectively. Transfection of miR-129-5p improved heart function and hemodynamic parameters, as well as attenuated oxidative stress and inflammation factors in CHF rats. We further confirmed that HMGB1 is a direct target of miR-129-5p. Transfection of miR-129-5p also decreased the mRNA and protein levels of HMGB1 in myocardial tissues of CHF rats. Overexpression of HMGB1 diminished the effects of miR-129-5p on ameliorating oxidative stress and inflammatory response in rats with CHF. Our findings suggest that miR-129-5p protects the heart by targeting HMGB1.

Abstract 042: Carotid Body Ablation of TRPV1 Reduces Chemoreflex Sensitivity in Rats With Heart Failure

Resiniferatoxin (RTX), an ultrapotent analogue of capsaicin, activates and destroys TRPV1 expressing cells. RTX in the CB may reduce abnormal breathing patterns seen in rats with HF. The purpose of this study was to examine whether TRPV1 ablation in the CB of HF rats alters chemoreflex-evoked ventilation and cardiovascular function. We used the post-MI model of HF in male SD rats (200-250g). BP (radiotelemetry), cardiac function (echocardiography) and ventilation (plethysmography measured under hypoxic (10% and 15% of O2) and hypercapnic (5% and 7% of CO2) conditions) before and 4 weeks after application of vehicle or RTX (50ug/ml) to the CB. After 4 weeks of MI, the rats showed ejection fraction of 35.9±1.6% demonstrating HF condition. Immunofluorescence showed lower expression of TRPV1 in RTX treated comparing to vehicle-treated CBs. RTX treatment (n=4) reduced baseline MAP (Veh=93.3±2.3 vs RTX=87.1±1.4, p<0.001) and HR (Veh=335.8±10.5 vs RTX=297±10.2, p<0.001) and normalized the increased ventilatory response to hypoxia or hypercapnia in HF rats (Figure). Poincare analyses showed an increase in the breath-breath variability 4 weeks after treatment with veh (SD1=95.9±14.3 vs 198.2±31.9; SD2=135.3±20.2 vs 279.9±45.1), which was blunt by RTX (SD1=87.5±17.7 vs 97.2±23.6; SD2=123.4±25 vs 137.1±33.4; p<0.05). No changes in BP, HR and body temperature were observed during hypoxia and hypercapnia in CHF rats, treated or not with RTX. These data show that CB RTX treatment in HF rats reduces chemoreflex sensitivity. These data implicate an enhanced role for TRPV1 signaling in chemoreflex function in HF.

OR-019 VEGF-B inhibits skeletal muscle apoptosis after exercise in Chronic heart failure rats

Objective To investigate the effects of vascular endothelial growth factor B in aerobic exercise mediated chronic heart failure rats cardiac function improvement and skeletal muscle remodeling.
 Methods We employed transverse abdominal aortic constriction (TAC) inducing CHF in Sprague Dawley rats. Controls were sham-operated animals. At 4 weeks after surgery, rats were randomized to 4 weeks of aerobic exercise (CHF+E) or to untrained groups (CHF). After 8 weeks, all rats went echocardiography test. After which, rats were sacrificed and samples were collected. Muscular cytokine VEGFB and its receptor NRP1 expression were analyzed. Expression of apoptosis and muscle atrophy markers were assessed in cardiac muscle、gastrocnemius.
 Results TAC rats developed CHF (preserved LV ejection fraction, hypertrophy of myocardial cells, decreased FS, increased LVAW d and LVID s). Exercise ameliorate CHF rat cardiac function. TAC rat skeletal muscle developed irregular muscle fiber distribution.The two atrophy-related ubiquitin ligases atrogin-1 and MuRF1, as well as genes involved in apoptosis and autophagy were upregulated in muscles in CHF rats. Exercise inhibited muscle atrophy and skeletal muscle apoptosis.VEGFB and its receptor NRPI decreased significantly in CHF muscle. Exercise promoted VEGFB and NRP1 expression in cardiac tissue, gastrocnemius.
 Conclusions Exercise ameliorates CHF rat cardiac function. VEGFB inhibits cardiac muscle and gastrocnemius apoptosis in CHF rats.

Abstract 555: Exosomal MicroRNAs Contribute to Chronic Heart Failure Through Dysregulating Nuclear Factor Erythroid 2-Related Factor 2/Antioxidant Response Element Signaling

The imbalance between the synthesis of free radicals and their elimination by antioxidant defense systems, results in macromolecular damage and disruption of cellular redox signaling, affecting cardiac structure and function, and thus contributing to the contractile dysfunction, myocardial hypertrophy and fibrosis. The Nrf2/Keap1/ARE signaling pathway is an important antioxidant defense mechanism and is closely associated with oxidative stress-mediated cardiac remodeling in CHF. Keap1, a redox-regulated substrate adaptor protein for the Cul3-dependent ubiquitin ligase complex generally mediates Nrf2 degradation. In this study, we hypothesized that circulating exosomal microRNAs may be involved in the translational repression of Nrf2 mRNA in the setting of CHF. We analyzed microRNA levels in exosomes from plasma of Sham and CHF rats. We found that three microRNAs including microRNA-27a, -28-3p and -34a which have potential binding sites in the 3’-UTR of Nrf2 mRNA, were highly enriched in exosomes derived from the circulation of CHF rats compared with sham rats (Fig.1). We labeled exosomes from CHF rats derived from plasma with PKH26 and administrated fluorescence-labeled exosomes into mice by various routes in order to track their distribution in vivo using the IVIS imaging system. Our preliminary data show that exosome distribution is dependent on the route of administration, and that circulating exosomes target the brain and heart. Taken together, these findings suggest that increased circulating exosomal microRNAs may contribute to Nrf2 dysregulation in CHF. These microRNAs may also serve as biomarkers for early diagnosis of CHF and therapeutic targets for CHF.

Safety and efficacy of Qishen granules in patients with chronic heart failure: study protocol for a randomized controlled trial

BackgroundChronic heart failure (CHF), the final stage of various cardiovascular diseases, is a major public health problem resulting in significant hospitalization rates, mortality, and huge health care costs despite advances in the treatment and management of heart failure and heart failure-related risk factors. Qishen granules (QSG), a Chinese herbal formula, is widely used by traditional Chinese medicine (TCM) practitioners to treat CHF. Several animal experimental studies have showed that QSG can significantly relieve the heart failure symptoms in CHF rat models. However, there is as yet no standard clinical trial to confirm this. Thus, the investigators are conducting this study to evaluate the efficacy and safety of QSG in a large, and varied population.Methods/designThis study is designed as a randomized, placebo-controlled, multi-center, double-blind clinical trial with parallel groups. A total of 200 patients with CHF will be recruited and randomly allocated to either the QSG treatment group or the placebo group (in a 1:1 ratio). The patients will receive QSG or placebo granules twice a day for 12 weeks. The primary outcome is the proportion of patients in the QSG group, compared with the placebo group, demonstrating a more than 30% decrease in NT-proBNP level during 12 weeks of treatment. The secondary outcomes consist of composite cardiac events, New York Heart Association functional classification, 6-minute walking distance, left ventricular ejection fraction, patient quality of life, and the TCM syndrome integral scale.DiscussionOn a background of standard treatment, QSG may further reduce the levels of NT-proBNP. This trial will provide high-quality evidence on the efficacy and safety of QSG in treating CHF, thus providing reference for clinical application of QSG.Trial registrationClinical Trials.gov: NCT03027375. Registered on 16 January 2017.

Behavioral Effects of Systemic, Infralimbic and Prelimbic Injections of a Serotonin 5-HT2A Antagonist in Carioca High- and Low-Conditioned Freezing Rats.

The role of serotonin (5-hydroxytryptamine [5-HT]) and 5-HT2A receptors in anxiety has been extensively studied, mostly without considering individual differences in trait anxiety. Our laboratory developed two lines of animals that are bred for high and low freezing responses to contextual cues that are previously associated with footshock (Carioca High-conditioned Freezing [CHF] and Carioca Low-conditioned Freezing [CLF]). The present study investigated whether ketanserin, a preferential 5-HT2A receptor blocker, exerts distinct anxiety-like profiles in these two lines of animals. In the first experiment, the animals received a systemic injection of ketanserin and were exposed to the elevated plus maze (EPM). In the second experiment, these two lines of animals received microinjections of ketanserin in the infralimbic (IL) and prelimbic (PL) cortices and were exposed to either the EPM or a contextual fear conditioning paradigm. The two rat lines exhibited bidirectional effects on anxiety-like behavior in the EPM and opposite responses to ketanserin. Both systemic and intra-IL cortex injections of ketanserin exerted anxiolytic-like effects in CHF rats but anxiogenic-like effects in CLF rats. Microinjections of ketanserin in the PL cortex also exerted anxiolytic-like effects in CHF rats but had no effect in CLF rats. These results suggest that the behavioral effects of 5-HT2A receptor antagonism might depend on genetic variability associated with baseline reactions to threatening situations and 5-HT2A receptor expression in the IL and PL cortices.Highlights -CHF and CLF rats are two bidirectional lines that are based on contextual fear conditioning.-CHF rats have a more “anxious” phenotype than CLF rats in the EPM.-The 5-HT2A receptor antagonist ketanserin had opposite behavioral effects in CHF and CLF rats.-Systemic and IL injections either decreased (CHF) or increased (CLF) anxiety-like behavior.-PL injections either decreased (CHF) anxiety-like behavior or had no effect (CLF).

Effects of l-arginine supplementation associated with continuous or interval aerobic training on chronic heart failure rats

ObjectiveChronic heart failure (CHF) is related with exercise intolerance and impaired nitric oxide (NO) production, which can lead to several functional capacity alterations. Considering the possible superiority of aerobic interval training compared to continuous training and the capacity of l-arginine to restore the NO pathway, the aim of the present study was to investigate whether these treatments are beneficial to exercise capacity, muscle mass preservation and hemodynamic, inflammatory and oxidative stress parameters in CHF rats. MethodsThirty-eight male Wistar rats post 6weeks of myocardial infarction (MI) surgery were randomly assigned into 6 CHF groups: sedentary (SED, n=6); SED+Arg (n=7); ACT (n=8); ACT+Arg (n=5); AIT (n=7); AIT+Arg (n=5). Exercise test capacity (ETC) was performed pre and post 8weeks of intervention. Supplemented rats received Arg (1g/kg) by oral gavage (7×/week). Exercise training was performed on a rat treadmill (5×/week). Hemodynamic variables, tissue collection, congestion, inflammatory cytokines, and oxidative parameters were evaluated at the end of protocols. ResultsAll trained groups showed a superior exercise capacity compared to SED groups on the post-intervention test (p<0.0001). Pulmonary congestion was attenuated in AIT and AIT+Arg compared with the SED group (p<0.05). Left ventricular end-diastolic pressure (LVEDP) was lower in ACT+Arg, AIT, and AIT+Arg groups than SED group (p<0.05). Association of AIT with Arg supplementation was able to improve hemodynamic responses (left ventricular systolic pressure (LVSP), systolic blood pressure (SBP), +dP/dtmax, and −dP/dtmax (p<0.05), likewise, decrease muscular and renal lipid peroxidation and tumor necrosis factor (TNF)-α, and increase interleukin (IL)-10/TNF-α plasmatic levels (p<0.01). Groups that associated aerobic exercise with Arg supplementation (ACT+Arg and AIT+Arg) revealed higher gastrocnemius mass compared to the SED group (p<0.01). ConclusionsBoth aerobic training protocols were capable to improve aerobic capacity, and the association with Arg supplementation was important to attenuate muscle loss. Moreover, interval training associated with Arg supplementation elicits greater improvements in hemodynamic parameters, contributing to reduction in pulmonary congestion, and demonstrated particular responses in the inflammatory profile and in the antioxidant status.

Decreased purinergic signaling in the RTN is associated with respiratory disorders in HFpEF rats

Heart failure with preserved ejection fraction (HFpEF) is characterized by the presence of respiratory disorders. Interestingly, it has been described that ATP‐mediated purinergic signaling (PSATP), in chemosensitive areas from the brainstem, contribute to central respiratory chemoreception. We recently described that HFpEF rats displays both resting breathing pattern irregularities and enhanced central chemoreflex drive. Therefore, we aimed to determine if HFpEF rats display alterations in the PSATP in the Retrotrapezoid nucleus (RTN), a major central chemosensitive area, and its possible role in the development of irregular breathing patterns in HFpEF. Adult male Sprague‐Dawley rats were subjected to volume overload to induce HFpEF. Whole body plethysmography was used to assess the ventilatory reflex response to hypercapnia to determine central chemoreceptors (CC) sensitivity. Resting breathing pattern was analyzed to score apneas/hypopneas incidence (AHI), as well as breath‐to‐breath (BB) interval variability. RTN micropunches were obtained for the study of PSATP protein expression and molecular markers of neuronal/astrocyte activation using immunoblot. ATP bioavailability in the RTN was determined using a high sensitive bioluminescence assay. Compared to control rats, HFpEF rats (Sham vs. CHF) display: increased AHI (9,7±1,1 vs. 20,2±1,6 events/hour, p&lt;.05), increased both the short‐term (SD1) and long‐term (SD2) BB interval variability (SD1: 42.8±8.0 vs.115,6±28,2; SD2: 54.5±9.0 vs. 138.4±33.1, p&lt;.05) and enhanced CC sensitivity (127.3±10.3 vs. 165.3±9.1 ml/min/100g, p&lt;.05). No changes in normoxic minute ventilation was found between sham and CHF condition. Also, we found that HFpEF rats compared to control rats (Sham vs. CHF) display similar FosB protein expression (p&gt;.05), decreased expression of GFAP (100±2.0% vs. 65±7.0%, p&lt;.05) without changes in S100β expression (85±11.8% vs. 100±9.5%, p&gt;.05) and decreased ATP bioavailable (78±2 vs. 21±10 pmoles/100μg of protein, p&lt;.05) in the RTN. In addition, we found that the P2X7 receptor was constitutively expressed both at the mRNA and protein levels in the RTN from sham rats and that CHF rats showed a significant decrease in the P2X7 receptor expression (45±8% vs. 100±15%, Sham vs. CHF, respectively, p&lt;.05). Remarkably, stereotaxic injection (2.5mm caudal to lambda, 1.8mm lateral to the midline and 7.5mm below the dura mater) of BzATP (200 μM/100 nl) into the RTN, a selective agonist of P2X7 receptor, markedly decrease the BB interval variability in sham rats (SD1: 100±8% vs. 45.7±5%; SD2: 100±8% vs. 40.7±5% pre vs. post BzATP, respectively, p&lt;.05) without changing resting tidal volume and/or respiratory frequency (p&gt;.05). In summary, our results show that HFpEF rats displayed astrocyte inhibition, reduced ATP bioavailability and decreased P2X7 receptor expression in the RTN along with a higher incidence of breathing irregularities compared to healthy animals. Together, our results suggest that altered breathing patterns in HFpEF may be associated with a decrease purinergic signalling in the RTN acting preferentially on P2X7 receptor within the RTN.Support or Funding InformationFONDECYT 1140275

Abstract 48: Differentiation of Moderate and Severe Ischemic Heart Failure by Invasive and Non-invasive Assessments of Diastolic Function in a Rat Model of Chronic Heart Failure

Background: This work is designed to determine if specific left ventricle (LV) pressure-volume relations, hemodynamic, and echo derived parameters of diastolic function are able to separate severe from moderate CHF in rats with left coronary artery occlusion. Hypothesis: Echocardiographic indices of diastolic function, end-diastolic pressure (EDP), dead volume, stiffness constants (k), and pressure volume relations predict the severity of CHF in infarcted rats. Methods: Male Sprague Dawley rats (N=14) were randomized to undergo left coronary artery ligation or sham operation. Echocardiography was performed at 3 and 6 weeks post coronary ligation. The rats were categorized into moderate or severe CHF according to their LVEDP at 6 weeks post ligation. Invasive hemodynamic measurements with solid state micro manometer pressure catheters as well as diastolic pressure-volume relation values were obtained at the 6 week end point. Results: Moderate and severe CHF rats had significantly (P&lt;0.05) elevated left ventricular (LV) end-diastolic pressure (LV EDPs), prolonged time constants of LV relaxation (tau), and decreased peak development pressures. When moderate versus severe CHF rats were separated based on LV EDP, early diastolic anterior wall radial relaxation velocity as well as e’, and E/e’ had strong correlations with invasive hemodynamic measurements of diastolic functions. There was a trend towards decreased compliance as measured by stiffness constants in severe heart failure group. Differences (P&lt;0.05) in dead volume, mean arterial pressure (MAP), tau, and ejection fraction (EF) were also displayed. End diastolic pressure-volume analyses illustrated significant differences in plot positioning and curvature. Conclusion: While it is possible to separate rats with moderate and severe CHF in the rat coronary artery ligation model, the separation is not simply based on a specific EF value. This work may be useful in deciding whether there is a differential effect of new treatments for severe versus moderate CHF.

Abstract P220: Congestive Heart Failure in the Rat Induces Subtle Renal Damage via Neurogenic Pathways

Background: Cardiomyopathy in experimental renal insufficiency is putatively influenced by neurogenic pathways of renal origin. We wondered if cardiac neurogenic effects in congestive heart failure could likewise harm the kidney. We hypothesized that increased renal sympathetic nerve activity (RSNA) in rats with congestive heart failure after myocardial infarction (CHF) induces renal structural damage. Methods: 21 day after induction of CHF renal morphology was evaluated by immunohistology (interstitial and glomerular mononuclear cell infiltration (ED1), cell proliferation (PCNA), collagen I,III,IV,V,VI, laminin und fibronectin). RSNA was assessed by volume challenge (VE) to decrease RSNA. CHF and control rats were investigated with and without renal denervation (DNX). Blood pressure (BP), heart rate (HR) and RSNA were recorded. Nodose ganglion neurons (NGN) with vagal cardiac afferents were cultured for 1 day. Whole cell recordings were obtained and current-voltage relationships established. Cells were characterized by osmomechanical stress with a mannitol solution. Results: In CHF rats with intact renal nerves (nonDNX) formation of collagen I occurred, that was reduced after DNX (12.2+0.7 %area vs. 9.1+1.1 %area*, n=6, * p&lt;0.05). VE-induced RSNA decreases were impaired in CHF vs controls suggesting increased RSNA (-α 34+8% vs. -α[[Unable to Display Character: &amp;#61472;]]54+6% *, n=6, * p&lt;0.05). NGN from CHF exhibited altered conductance in response to mechanical stress as compared to controls (change in holding current at -80 mV: control_normoosmotic: -144±30 pA; control_hypoos.: -282±34 pA vs CHF_normosmotic: - 230±55 pA; CHF_hypos.: -540±100* pA; *p&lt;0.05 CHF vs. control). Conclusion: CHF induced subtle renal structural damage due to increased renal sympathetic tone which was likely due to altered NGN mechanosensitivity. Afferent nerve units from cardiovascular organs obviously form a complex sympathomodulatory network.