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Background: Purinergic P2Y 1 and P2Y 12 receptors (P2Y 1 -R and P2Y 12 -R) are G protein-coupled receptors (GPCR) activated by adenosine diphosphate (ADP) to mediate platelet activation, thereby playing a pivotal role in hemostasis and thrombosis. While P2Y 12 -R is the major target of antiplatelet drugs, no P2Y 1 -R antagonist has yet been developed for clinical use. However, accumulating data suggest that P2Y 1 -R inhibition would ensure efficient platelet inhibition with minimal effects on bleeding. In this context, an accurate characterization of P2Y 1 -R antagonists constitutes an important preliminary step., Results: Here, we investigated the pharmacology of P2Y 1 -R signaling through Gq and β-arrestin pathways in HEK293T cells and in mouse and human platelets using highly sensitive resonance energy transfer-based technologies (BRET/HTRF). We demonstrated that at basal state, in the absence of agonist ligand, P2Y 1 -R activates Gq protein signaling in HEK293T cells and in mouse and human platelets, indicating that P2Y 1 -R is constitutively active in physiological conditions. We showed that P2Y 1 -R also promotes constitutive recruitment of β-arrestin 2 in HEK293T cells. Moreover, the P2Y 1 -R antagonists MRS2179, MRS2279 and MRS2500 abolished the receptor dependent-constitutive activation, thus behaving as inverse agonists., Conclusions: This study sheds new light on P2Y 1 -R pharmacology, highlighting for the first time the existence of a constitutively active P2Y 1 -R population in human platelets. Given the recent interest of P2Y 12 -R constitutive activity in patients with diabetes, this study suggests that modification of constitutive P2Y 1 -R signaling might be involved in pathological conditions, including bleeding syndrome or high susceptibility to thrombotic risk. Thus, targeting platelet P2Y 1 -R constitutive activation might be a promising and powerful strategy for future antiplatelet therapy., (© 2023. The Author(s).)

G protein-coupled receptors (GPCRs) form the largest family of cell surface receptors. Despite considerable insights into their pharmacology, the GPCR architecture at the cell surface still remains largely unexplored. Herein, we present the specific unfolding of different GPCRs at the surface of living mammalian cells by atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS). Mathematical analysis of the GPCR unfolding distances at resting state revealed the presence of different receptor populations relying on distinct oligomeric states which are receptor-specific and receptor expression-dependent. Moreover, we show that the oligomer size dictates the receptor spatial organization with nanoclusters of high-order oligomers while lower-order complexes spread over the whole cell surface. Finally, the receptor activity reshapes both the oligomeric populations and their spatial arrangement. These results add an additional level of complexity to the GPCR pharmacology until now considered to arise from a single receptor population at the cell surface., (© 2022. The Author(s).)

Restricted and controlled drug delivery to the heart remains a challenge giving frequent off-target effects as well as limited retention of drugs in the heart. There is a need to develop and optimize tools to allow for improved design of drug candidates for treatment of heart diseases. Over the last decade, novel drug platforms and nanomaterials were designed to confine bioactive materials to the heart. Yet, the research remains in its infancy, not only in the development of tools but also in the understanding of effects of these materials on cardiac function and tissue integrity. Upconverting nanoparticles are nanomaterials that recently accelerated interest in theranostic nanomedicine technologies. Their unique photophysical properties allow for sensitive in vivo imaging that can be combined with spatio-temporal control for targeted release of encapsulated drugs. Here we synthesized upconverting NaYF4:Yb,Tm nanoparticles and show for the first time their innocuity in the heart, when injected in the myocardium or in the pericardial space in mice. Nanoparticle retention and upconversion in the cardiac region did not alter heart rate variability, nor cardiac function as determined over a 15-day time course ensuing the sole injection. Altogether, our nanoparticles show innocuity primarily in the pericardial region and can be safely used for controlled spatiotemporal drug delivery. Our results support the use of upconverting nanoparticles as potential theranostics tools overcoming some of the key limitations associated with conventional experimental cardiology., Competing Interests: The authors have declared that no competing interests exist.

Background: Exaggerated sympathetic nervous system activity associated with low heart rate variability (HRV) is considered to trigger cardiac arrhythmias and sudden death. Regular exercise training is efficient to improve autonomic balance., Objective: We aimed to verify the superiority of high-intensity interval training (HIIT) to enhance HRV, cardiorespiratory fitness and cardiac function as compared with moderate intensity continuous training (MICT) in a short, intense cardiac rehabilitation program., Methods: This was a prospective, monocentric, evaluator-blinded, randomised (1:1) study with a parallel two-group design. Overall, 31 individuals with voluntary chronic heart failure (CHF) (left ventricular ejection fraction [LVEF]<45%) were allocated to MICT (n=15) or HIIT (n=16) for a short rehabilitation program (mean [SD] 27 [4] days). Participants underwent 24-hr electrocardiography, echocardiography and a cardiopulmonary exercise test at entry and at the end of the study., Results: High-frequency power in normalized units (HFnu%) measured as HRV increased with HIIT (from 21.2% to 26.4%, P<0.001) but remained unchanged with MICT (from 23.1% to 21.9%, P=0.444, with a significant intergroup difference, P=0.003). Resting heart rate (24-hr Holter electrocardiography) decreased significantly for both groups (from 68.2 to 64.6 bpm and 66.0 to 63.5 bpm for MICT and HIIT, respectively, with no intergroup difference, P=0.578). The 2 groups did not differ in premature ventricular contractions. Improvement in peak oxygen uptake was greater with HIIT than MICT (+21% vs. +5%, P=0.009). LVEF improved with only HIIT (from 36.2% to 39.5%, P=0.034)., Conclusions: In this short rehabilitation program, HIIT was significantly superior to the classical MICT program for enhancing parasympathetic tone and peak oxygen uptake. CLINICALTRIALS., Gov Identifier: NCT03603743., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Aims: This study explored the lateral crest structures of adult cardiomyocytes (CMs) within healthy and diseased cardiac tissue., Methods and Results: Using high-resolution electron and atomic force microscopy, we performed an exhaustive quantitative analysis of the three-dimensional (3D) structure of the CM lateral surface in different cardiac compartments from various mammalian species (mouse, rat, cow, and human) and determined the technical pitfalls that limit its observation. Although crests were observed in nearly all CMs from all heart compartments in all species, we showed that their heights, dictated by the subsarcolemmal mitochondria number, substantially differ between compartments from one species to another and tightly correlate with the sarcomere length. Differences in crest heights also exist between species; for example, the similar cardiac compartments in cows and humans exhibit higher crests than rodents. Unexpectedly, we found that lateral surface crests establish tight junctional contacts with crests from neighbouring CMs. Consistently, super-resolution SIM or STED-based immunofluorescence imaging of the cardiac tissue revealed intermittent claudin-5-claudin-5 interactions in trans via their extracellular part and crossing the basement membrane. Finally, we found a loss of crest structures and crest-crest contacts in diseased human CMs and in an experimental mouse model of left ventricle barometric overload., Conclusion: Overall, these results provide the first evidence for the existence of differential CM surface crests in the cardiac tissue as well as the existence of CM-CM direct physical contacts at their lateral face through crest-crest interactions. We propose a model in which this specific 3D organization of the CM lateral membrane ensures the myofibril/myofiber alignment and the overall cardiac tissue cohesion. A potential role in the control of sarcomere relaxation and of diastolic ventricular dysfunction is also discussed. Whether the loss of CM surface crests constitutes an initial and common event leading to the CM degeneration and the setting of heart failure will need further investigation., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2018. For permissions, please email: journals.permissions@oup.com.)

P2Y 12 receptor (P2Y 12 -R) is one of the major targets for drug inhibiting platelet aggregation in the treatment/prevention of arterial thrombosis. However, the clinical use of P2Y 12 -R antagonists faces some limitations, such as a delayed onset of action (clopidogrel) or adverse effect profile (ticagrelor, cangrelor), justifying the development of a new generation of P2Y 12 -R antagonists with a better clinical benefit-risk balance. Although the recent concept of biased agonism offers the possibility to alleviate undesirable adverse effects while preserving therapeutic outcomes, it has never been explored at P2Y 12 -R. For the first time, using highly sensitive BRET2-based probes, we accurately delineated biased ligand efficacy at P2Y 12 -R in living HEK293T cells on G protein activation and downstream effectors. We demonstrated that P2Y 12 -R displayed constitutive Gi/o-dependent signaling that is impaired by the R122C mutation, previously associated with a bleeding disorder. More importantly, we reported the biased inverse agonist efficacy of cangrelor and ticagrelor that could underlie their clinical efficacy. Our study points out that constitutive P2Y 12 -R signaling is a normal feature of the receptor that might be essential for platelets to respond faster to a vessel injury. From a therapeutic standpoint, our data suggest that the beneficial advantages of antiplatelet drugs might be more related to inverse agonism at P2Y 12 -R than to antagonism of ADP-mediated signaling. In the future, deciphering P2Y 12 -R constitutive activity should allow the discovery of more selective biased P2Y 12 -R blockers demonstrating therapeutic advantages over classical antiplatelet drugs by improving therapeutic outcomes and concomitantly relieving undesirable adverse effects.

Biased agonism at G protein coupled receptors emerges as an opportunity for development of drugs with enhanced benefit/risk balance making biased ligand identification a priority. However, ligand biased signature, classically inferred from ligand activity across multiple pathways, displays high variability in recombinant systems. Functional assays usually necessity receptor/effector overexpression that should be controlled among assays to allow comparison but this calibration currently fails. Herein, we demonstrate that Gα expression level dictates the biased profiling of agonists and, to a lesser extent of β-blockers, in a Gα isoform- and receptor-specific way, depending on specific G protein activity in different membrane territories. These results have major therapeutic implications since they suggest that the ligand bias phenotype is not necessarily maintained in pathological cell background characterized by fluctuations in G protein expression. Thus, we recommend implementation of G protein stoichiometry as a new parameter in biased ligand screening programs.

Background: In patients with peripheral arterial disease (PAD), walking improvements are often limited by early pain onset due to vascular claudication. It would thus appear interesting to develop noninvasive therapeutic strategies, such as transcutaneous electrical nerve stimulation (TENS), to improve the participation of PAD patients in rehabilitation programmes, and thus improve their quality of life. Our team recently tested the efficacy of a single 45-min session of 10-Hz TENS prior to walking. TENS significantly delayed pain onset and increased the pain-free walking distance in patients with class-II PAD. We now seek to assess the efficacy of a chronic intervention that includes the daily use of TENS for 3 weeks (5 days a week) on walking distance in Leriche-Fontaine stage-II PAD patients., Methods/design: This is a prospective, double-blind, multicentre, randomised, placebo-controlled trial. One hundred subjects with unilateral PAD (Leriche-Fontaine stage II) will be randomised into two groups (1:1). For the experimental group (TENS group): the treatment will consist of stimulation of the affected leg (at a biphasic frequency of 10 Hz, with a pulse width of 200 μs, maximal intensity below the motor threshold) for 45 min per day, in the morning before the exercise rehabilitation programme, for 3 weeks, 5 days per week. For the control group (SHAM group): the placebo stimulation will be delivered according to the same modalities as for the TENS group but with a voltage level automatically falling to zero after 10 s of stimulation. First outcome: walking distance without pain., Secondary Outcomes: transcutaneous oxygen pressure (TcPO 2 ) measured during a Strandness exercise test, peak oxygen uptake (VO 2 peak), endothelial function (EndoPAT®), Ankle-brachial Pressure Index, Body Mass Index, lipid profile (LDL-C, HDL-C, triglycerides), fasting glycaemia, HbA1c level, and the WELCH questionnaire., Discussion: TENS-PAD is the first randomised controlled trial that uses transcutaneous electrical therapy as an adjuvant technique to improve vascular function in the treatment of PAD. If the results are confirmed, this technique could be incorporated into the routine care in cardiovascular rehabilitation centers and used in the long term by patients to improve their walking capacity., Trial Registration: ClinicalTrials.gov, ID: NCT02678403 . Registered on 9 February 2016., Sponsor: Toulouse University Hospital.

PeakForce Quantitative Nanomechanical Mapping (PeakForce QNM) multiparametric AFM mode was adapted to qualitative and quantitative study of the lateral membrane of cardiomyocytes (CMs), extending this powerful mode to the study of soft cells. On living CM, PeakForce QNM depicted the crests and hollows periodic alternation of cell surface architecture previously described using AFM Force Volume (FV) mode. PeakForce QNM analysis provided better resolution in terms of pixel number compared to FV mode and reduced acquisition time, thus limiting the consequences of spontaneous living adult CM dedifferentiation once isolated from the cardiac tissue. PeakForce QNM mode on fixed CMs clearly visualized subsarcolemmal mitochondria (SSM) and their loss following formamide treatment, concomitant with the interfibrillar mitochondria climbing up and forming heaps at the cell surface. Interestingly, formamide-promoted SSM loss allowed visualization of the sarcomeric apparatus ultrastructure below the plasma membrane. High PeakForce QNM resolution led to better contrasted mechanical maps than FV mode and provided correlation between adhesion, dissipation, mechanical and topographical maps. Modified hydrophobic AFM tip enhanced contrast on adhesion and dissipation maps and suggested that CM surface crests and hollows exhibit distinct chemical properties. Finally, two-dimensional Fast Fourier Transform to objectively quantify AFM maps allowed characterization of periodicity of both sarcomeric Z-line and M-band. Overall, this study validated PeakForce QNM as a valuable and innovative mode for the exploration of living and fixed CMs. In the future, it could be applied to depict cell membrane architectural, mechanical and chemical defects as well as sarcomeric abnormalities associated with cardiac diseases., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Patients with cardiovascular disease show autonomic dysfunction, including sympathetic activation and vagal withdrawal, which leads to fatal events. This review aims to place sympathovagal balance as an essential element to be considered in management for cardiovascular disease patients who benefit from a cardiac rehabilitation program. Many studies showed that exercise training, as non-pharmacologic treatment, plays an important role in enhancing sympathovagal balance and could normalize levels of markers of sympathetic flow measured by microneurography, heart rate variability or plasma catecholamine levels. This alteration positively affects prognosis with cardiovascular disease. In general, cardiac rehabilitation programs include moderate-intensity and continuous aerobic exercise. Other forms of activities such as high-intensity interval training, breathing exercises, relaxation and transcutaneous electrical stimulation can improve sympathovagal balance and should be implemented in cardiac rehabilitation programs. Currently, the exercise training programs in cardiac rehabilitation are individualized to optimize health outcomes. The sports science concept of the heart rate variability (HRV)-vagal index used to manage exercise sessions (for a goal of performance) could be implemented in cardiac rehabilitation to improve cardiovascular fitness and autonomic nervous system function., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Background: Isometric strengthening has been rarely studied in patients with coronary heart disease (CHD), mainly because of possible potential side effects and lack of appropriate and reliable devices., Objective: We aimed to compare 2 different modes of resistance training, an isometric mode with the Huber Motion Lab (HML) and traditional strength training (TST), in CHD patients undergoing a cardiac rehabilitation program., Design: We randomly assigned 50 patients to HML or TST. Patients underwent complete blinded evaluation before and after the rehabilitation program, including testing for cardiopulmonary exercise, maximal isometric voluntary contraction, endothelial function and body composition., Results: After 4 weeks of training (16 sessions), the groups did not differ in body composition, anthropometric characteristics, or endothelial function. With HML, peak power output (P=0.035), maximal heart rate (P<0.01) and gain of force measured in the chest press position (P<0.02) were greater after versus before training., Conclusion: Both protocols appeared to be well tolerated, safe and feasible for these CHD patients. A training protocol involving 6s phases of isometric contractions with 10s of passive recovery on an HML device could be safely implemented in rehabilitation programs for patients with CHD and improve functional outcomes., (Copyright © 2016. Published by Elsevier Masson SAS.)

Hyperactivity of the renin-angiotensin-aldosterone system through the angiotensin II (Ang II)/Ang II type 1 receptor (AT1-R) axis constitutes a hallmark of hypertension. Recent findings indicate that only a subset of AT1-R signaling pathways is cardiodeleterious, and their selective inhibition by biased ligands promotes therapeutic benefit. To date, only synthetic biased ligands have been described, and whether natural renin-angiotensin-aldosterone system peptides exhibit functional selectivity at AT1-R remains unknown. In this study, we systematically determined efficacy and potency of Ang II, Ang III, Ang IV, and Ang-(1-7) in AT1-R-expressing HEK293T cells on the activation of cardiodeleterious G-proteins and cardioprotective β-arrestin2. Ang III and Ang IV fully activate similar G-proteins than Ang II, the prototypical AT1-R agonist, despite weaker potency of Ang IV. Interestingly, Ang-(1-7) that binds AT1-R fails to promote G-protein activation but behaves as a competitive antagonist for Ang II/Gi and Ang II/Gq pathways. Conversely, all renin-angiotensin-aldosterone system peptides act as agonists on the AT1-R/β-arrestin2 axis but display biased activities relative to Ang II as indicated by their differences in potency and AT1-R/β-arrestin2 intracellular routing. Importantly, we reveal Ang-(1-7) a known Mas receptor-specific ligand, as an AT1-R-biased agonist, selectively promoting β-arrestin activation while blocking the detrimental Ang II/AT1-R/Gq axis. This original pharmacological profile of Ang-(1-7) at AT1-R, similar to that of synthetic AT1-R-biased agonists, could, in part, contribute to its cardiovascular benefits. Accordingly, in vivo, Ang-(1-7) counteracts the phenylephrine-induced aorta contraction, which was blunted in AT1-R knockout mice. Collectively, these data suggest that Ang-(1-7) natural-biased agonism at AT1-R could fine-tune the physiology of the renin-angiotensin-aldosterone system., (© 2016 American Heart Association, Inc.)

During the last 10 years, the concept of "biased agonism" also called "functional selectivity" swamped the pharmacology of 7 transmembrane receptors and paved the way for developing signaling pathway-selective drugs with increased efficacy and less adverse effects. Initially thought to select the activation of only a subset of the signaling pathways by the reference agonist, bias ligands revealed higher complexity as they have been shown to stabilize variable receptor conformations that associate with distinct signaling events from the reference. Today, one major challenge relies on the in vitro determination of the bias and classification of these ligands, as a prerequisite for future in vivo and clinical translation. In this review, current experimental considerations for the bias evaluation related to choice of the cellular model, of the signaling pathway as well as of the assays are presented and discussed., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Objective: The aim of this study was to determine whether 45 mins of transcutaneous electrical nerve stimulation before exercise could delay pain onset and increase walking distance in peripheral artery disease patients., Design: After a baseline assessment of the walking velocity that led to pain after 300 m, 15 peripheral artery disease patients underwent four exercise sessions in a random order. The patients had a 45-min transcutaneous electrical nerve stimulation session with different experimental conditions: 80 Hz, 10 Hz, sham (presence of electrodes without stimulation), or control with no electrodes, immediately followed by five walking bouts on a treadmill until pain occurred. The patients were allowed to rest for 10 mins between each bout and had no feedback concerning the walking distance achieved., Results: Total walking distance was significantly different between T10, T80, sham, and control (P < 0.0003). No difference was observed between T10 and T80, but T10 was different from sham and control. Sham, T10, and T80 were all different from control (P < 0.001). There was no difference between each condition for heart rate and blood pressure., Conclusions: Transcutaneous electrical nerve stimulation immediately before walking can delay pain onset and increase walking distance in patients with class II peripheral artery disease, with transcutaneous electrical nerve stimulation of 10 Hz being the most effective.

Hypersecretion of norepinephrine (NE) and angiotensin II (AngII) is a hallmark of major prevalent cardiovascular diseases that contribute to cardiac pathophysiology and morbidity. Herein, we explore whether heterodimerization of presynaptic AngII AT1 receptor (AT1-R) and NE α2C-adrenergic receptor (α2C-AR) could underlie their functional cross-talk to control NE secretion. Multiple bioluminescence resonance energy transfer and protein complementation assays allowed us to accurately probe the structures and functions of the α2C-AR-AT1-R dimer promoted by ligand binding to individual protomers. We found that dual agonist occupancy resulted in a conformation of the heterodimer different from that induced by active individual protomers and triggered atypical Gs-cAMP-PKA signaling. This specific pharmacological signaling unit was identified in vivo to promote not only NE hypersecretion in sympathetic neurons but also sympathetic hyperactivity in mice. Thus, we uncovered a new process by which GPCR heterodimerization creates an original functional pharmacological entity and that could constitute a promising new target in cardiovascular therapeutics.

Breast cancer is the most frequent malignancy in women. Several reports demonstrated that adrenergic receptors (ARs) are involved in breast cancer. Here we observed that epinephrine (Epi), an endogenous AR agonist, caused opposite effects in non-tumorigenic (MCF-10A and HBL-100) and tumor cells (MCF-7 and MDA-MB-231). Thus, Epi, in non-tumor breast cells, as well as isoproterenol (β-agonist), in all cell lines, maintained a benign phenotype, decreasing cell proliferation and migration, and stimulating cell adhesion. β-AR expression and cAMP levels were higher in MCF-10A than in MCF-7 cells. β₂-AR knock-down caused a significant increase of cell proliferation and migration, and a decrease of cell adhesion both in basal and in Iso-stimulated conditions. Coincidently, β₂-AR over-expression induced a significant decrease of cell proliferation and migration, and an increase of cell adhesion. Therefore, β₂-AR is implied in cell phenotype and its agonists or antagonists could eventually complement cancer therapy.

Loss of T-tubules (TT), sarcolemmal invaginations of cardiomyocytes (CMs), was recently identified as a general heart failure (HF) hallmark. However, whether TT per se or the overall sarcolemma is altered during HF process is still unknown. In this study, we directly examined sarcolemmal surface topography and physical properties using Atomic Force Microscopy (AFM) in living CMs from healthy and failing mice hearts. We confirmed the presence of highly organized crests and hollows along myofilaments in isolated healthy CMs. Sarcolemma topography was tightly correlated with elasticity, with crests stiffer than hollows and related to the presence of few packed subsarcolemmal mitochondria (SSM) as evidenced by electron microscopy. Three days after myocardial infarction (MI), CMs already exhibit an overall sarcolemma disorganization with general loss of crests topography thus becoming smooth and correlating with a decreased elasticity while interfibrillar mitochondria (IFM), myofilaments alignment and TT network were unaltered. End-stage post-ischemic condition (15days post-MI) exacerbates overall sarcolemma disorganization with, in addition to general loss of crest/hollow periodicity, a significant increase of cell surface stiffness. Strikingly, electron microscopy revealed the total depletion of SSM while some IFM heaps could be visualized beneath the membrane. Accordingly, mitochondrial Ca(2+) studies showed a heterogeneous pattern between SSM and IFM in healthy CMs which disappeared in HF. In vitro, formamide-induced sarcolemmal stress on healthy CMs phenocopied post-ischemic kinetics abnormalities and revealed initial SSM death and crest/hollow disorganization followed by IFM later disarray which moved toward the cell surface and structured heaps correlating with TT loss. This study demonstrates that the loss of crest/hollow organization of CM surface in HF occurs early and precedes disruption of the TT network. It also highlights a general stiffness increased of the CM surface most likely related to atypical IFM heaps while SSM died during HF process. Overall, these results indicate that initial sarcolemmal stress leading to SSM death could underlie subsequent TT disarray and HF setting., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The role of β-adrenergic receptors (β-ARs) remains controversial in normal and tumor breast. Herein we explore the cAMP signaling involved in β-AR-dependent control of proliferation and adhesion of nontumor human breast cell line MCF-10A. Low concentrations of a β-agonist, isoproterenol (ISO), promote cell adhesion (87.5% cells remaining adherent to the plastic dishes following specific detachment vs. 35.0% in control, P<0.001), while increasing concentrations further engages an additional 36% inhibition of Erk1/2 phosphorylation (p-Erk1/2)-dependent cell proliferation (P<0.01). Isoproterenol dose response on cell adhesion was fitted to a 2-site curve (EC50(1): 16.5±11.5 fM, EC50(2): 4.08±3.09 nM), while ISO significantly inhibited p-Erk1/2 according to a 1-site model (EC50: 0.25±0.13 nM). Using β-AR-selective agonist/antagonists and cAMP analogs/inhibitors, we identified a dosage-dependent signaling in which low ISO concentrations target a β2-AR population localized in raft microdomains and stimulate a Gs/cAMP/Epac/adhesion-signaling module, while higher concentrations engage a concomitant activation of another β2-AR population outside rafts and inhibit the proliferation by a Gs/cAMP/PKA-dependent signaling module. Our data provide a new molecular basis for the dose-dependent switch of β-AR signaling. This study also sheds light on a new cAMP pathway core mechanism with a single receptor triggering dual cAMP signaling controlled by PKA or Epac but with different cellular outputs.

Sympathetic nervous system (SNS) plays a key role in cardiac homeostasis and its deregulations always associate with bad clinical outcomes. To date, little is known about molecular mechanisms regulating cardiac sympathetic innervation. The aim of the study was to determine the role of fibroblasts in heart sympathetic innervation. RT-qPCR and western-blots analysis performed in cardiomyocytes and fibroblasts isolated from healthy adult rat hearts revealed that Pro-Nerve growth factor (NGF) and pro-differentiating mature NGF were the most abundant neurotrophins expressed in cardiac fibroblasts while barely detectable in cardiomyocytes. When cultured with cardiac fibroblasts or fibroblast-conditioned medium, PC12 cells differentiated into/sympathetic-like neurons expressing axonal marker Tau-1 at neurites in contact with cardiomyocytes. This was prevented by anti-NGF blocking antibodies suggesting a paracrine action of NGF secreted by fibroblasts. When co-cultured with cardiomyocytes to mimic neurocardiac synapse, differentiated PC12 cells exhibited enhanced norepinephrine secretion as quantified by HPLC compared to PC12 cultured alone while co-culture with fibroblasts had no effect. However, when supplemented to PC12-cardiomyocytes co-culture, fibroblasts allowed long-term survival of the neurocardiac synapse. Activated fibroblasts (myofibroblasts) isolated from myocardial infarction rat hearts exhibited significantly higher mature NGF expression than normal fibroblasts and also promoted PC12 cells differentiation. Within the ischemic area lacking cardiomyocytes and neurocardiac synapses, tyrosine hydroxylase immunoreactivity was increased and associated with local anarchical and immature sympathetic hyperinnervation but tissue norepinephrine content was similar to that of normal cardiac tissue, suggesting depressed sympathetic function. Collectively, these findings demonstrate for the first time that fibroblasts are essential for the setting of cardiac sympathetic innervation and neurocardiac synapse stability. They also suggest that neurocardiac synapse functionality relies on a triptych with tight interaction between sympathetic nerve endings, cardiomyocytes and fibroblasts. Deregulations of this triptych may be involved in pathophysiology of cardiac diseases.

Purpose: Autonomic dysfunction including sympathetic activation and vagal withdrawal has been reported in patients with chronic heart failure (CHF). We tested the hypotheses that high-intensity interval exercise (HIIE) in CHF patients would enhance vagal modulation and thus decrease arrhythmic events., Methods: Eighteen CHF patients underwent a baseline assessment (CON) and were then randomized to a single session of HIIE and to an isocaloric moderate-intensity continuous exercise (MICE). We evaluated the HR, HR variability parameters, and arrhythmic events by 24-h Holter ECG recordings after HIIE, MICE, and CON sessions., Results: We found that HR was significantly decreased after HIIE (68 ± 3 bpm, P < 0.01) when compared with CON and MICE values (71.1 ± 2 and 69 ± 3 bpm, respectively). HIIE led to a significant increase in normalized high-frequency power (35.95% ± 2.83% vs 31.56% ± 1.93% and 24.61% ± 2.62% for CON and MICE, respectively, P < 0.01). Both exercise conditions were associated with an increase in very low frequency power comparative to CON. After HIIE, premature ventricular contractions were significantly decreased (531 ± 338 vs 1007 ± 693 and 1671 ± 1604 for CON and MICE, respectively, P < 0.01). An association was found between the changes in premature ventricular contraction and the changes in low-frequency/high-frequency ratio (r = 0.66, P < 0.01) in patients exposed to HIIE., Conclusion: We demonstrate that a single session of HIIE improves autonomic profile of CHF patients, leading to significant reductions of HR and arrhythmic events in a 24-h posttraining period. Cardioprotective effects of HIIE in CHF patients need to be confirmed in a larger study population and on a long-term basis.

All cardiomyopathies and more specifically myocardial infarction always evolve to cardiomyocytes death and the ensuing heart failure setting. So far, cardiac regenerative medicine has focused on the use of stem cells and completely ignored the resident cardiomyocytes, assumed in a postmitotic state. However, recent findings in zebrafish and mammalians challenge this view and suggest that these cells have some capacity to proliferate and can contribute to heart regeneration. In this review, we propose an overall synthesis about knowledge of the proliferative and regenerative capacities of resident cardiomyocytes, dealing with some mechanistic aspects. In the future, the accurate identification of molecular mechanisms allowing wake-up of resident cardiomyocyte proliferation will certainly open new therapeutic avenues in cardiac regeneration., (© 2012 médecine/sciences – Inserm / SRMS.)

Functional selectivity of G protein-coupled receptor (GPCR) ligands toward different downstream signals has recently emerged as a general hallmark of this receptor class. However, pleiotropic and crosstalk signaling of GPCRs makes functional selectivity difficult to decode. To look from the initial active receptor point of view, we developed new, highly sensitive and direct bioluminescence resonance energy transfer-based G protein activation probes specific for all G protein isoforms, and we used them to evaluate the G protein-coupling activity of [(1)Sar(4)Ile(8)Ile]-angiotensin II (SII), previously described as an angiotensin II type 1 (AT(1)) receptor-biased agonist that is G protein independent but β-arrestin selective. By multiplexing assays sensing sequential signaling events, from receptor conformations to downstream signaling, we decoded SII as an agonist stabilizing a G protein-dependent AT(1A) receptor signaling module different from that of the physiological agonist angiotensin II, both in recombinant and primary cells. Thus, a biased agonist does not necessarily select effects from the physiological agonist but may instead stabilize and create a new distinct active pharmacological receptor entity.

At a time when pharmaceutical companies are having trouble finding new low MW drugs and when biologics are becoming more common, animal venoms could constitute an underexploited source of novel drug candidates. We looked for identifying novel animal toxins active against G protein-coupled receptors (GPCR), the most frequently exploited class of treatment targets, with the aim to develop novel research tools and drug candidates. Screening of green mamba (Dendroaspis angusticeps) venom against adrenoceptors identified two novel venom peptides. ρ-Da1a shown an affinity of 0.35 nM for the α1a-AR while ρ-Da1b displayed affinities between 14 and 73 nM for the three α2-ARs. These two venom peptides have sequences similar to those of muscarinic toxins and belong to the three-finger-fold protein family. α1a-AR is the primary target for the treatment of prostate hypertrophy. In vitro and in vivo tests demonstrated that ρ-Da1a reduced prostatic muscle tone as efficiently as tamsulosin (an antagonist presently used), but with fewer cardiovascular side effects. α2-ARs are the prototype of GPCRs not currently used as treatment targets due to a lack of specific ligands. Blockage of these receptors increases intestinal motility, which may be compromised by abdominal surgery and reduces orthosteric hypotension. In vitro and in vivo tests demonstrated that ρ-Da1b antagonizes α2-ARs in smooth muscles and increased heart rate and blood catecholamine concentrations. These results highlight possible exploitation of ρ-Da1a and ρ-Da1b in important pathologies., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Rationale: Cardiac tissue cohesion relying on highly ordered cardiomyocytes (CM) interactions is critical because most cardiomyopathies are associated with tissue remodeling and architecture alterations., Objective: Eph/ephrin system constitutes a ubiquitous system coordinating cellular communications which recently emerged as a major regulator in adult organs. We examined if eph/ephrin could participate in cardiac tissue cyto-organization., Methods and Results: We reported the expression of cardiac ephrin-B1 in both endothelial cells and for the first time in CMs where ephrin-B1 localized specifically at the lateral membrane. Ephrin-B1 knock-out (KO) mice progressively developed cardiac tissue disorganization with loss of adult CM rod-shape and sarcomeric and intercalated disk structural disorganization confirmed in CM-specific ephrin-B1 KO mice. CMs lateral membrane exhibited abnormal structure by electron microscopy and notably increased stiffness by atomic force microscopy. In wild-type CMs, ephrin-B1 interacted with claudin-5/ZO-1 complex at the lateral membrane, whereas the complex disappeared in KO/CM-specific ephrin-B1 KO mice. Ephrin-B1 deficiency resulted in decreased mRNA expression of CM basement membrane components and disorganized fibrillar collagen matrix, independently of classical integrin/dystroglycan system. KO/CM-specific ephrin-B1 KO mice exhibited increased left ventricle diameter and delayed atrioventricular conduction. Under pressure overload stress, KO mice were prone to death and exhibited striking tissue disorganization. Finally, failing CMs displayed downregulated ephrin-B1/claudin-5 gene expression linearly related to the ejection fraction., Conclusions: Ephrin-B1 is necessary for cardiac tissue architecture cohesion by stabilizing the adult CM morphology through regulation of its lateral membrane. Because decreased ephrin-B1 is associated with molecular/functional cardiac defects, it could represent a new actor in the transition toward heart failure.

Cell surface G protein-coupled receptors (GPCRs) drive numerous signaling pathways involved in the regulation of a broad range of physiologic processes. Today, they represent the largest target for modern drugs development with potential application in all clinical fields. Recently, the concept of "ligand-directed trafficking" has led to a conceptual revolution in pharmacological theory, thus opening new avenues for drug discovery. Accordingly, GPCRs do not function as simple on-off switch but rather as filters capable of selecting the activation of specific signals and thus generating texture responses to ligands, a phenomenon often referred to as ligand-biased signaling. Also, one challenging task today remains optimization of pharmacological assays with increased sensitivity so to better appreciate the inherent texture of ligands. However, considering that a single receptor has pleiotropic signaling properties and that each signal can crosstalk at different levels, biased activity remains thus difficult to evaluate. One strategy to overcome these limitations would be examining the initial steps following receptor activation. Even, if some G protein independent functions have been recently described, heterotrimeric G protein activation remains a general hallmark for all GPCRs families and the first cellular event subsequent to agonist binding to the receptor. Herein, we review the different methodologies classically used or recently developed to monitor G protein activation and discussed them in the context of G protein biased-ligands.

Objective: To improve the quality of proton pump inhibitors (PPI) prescription in an orthopaedic department., Study Design: Prospective professional practice evaluation study., Patients and Methods: A specific protocol concerning the best practice for using PPI in the perioperative period was established by anaesthesiologists and validated by all prescribers, according to recent recommendations published by French Afssaps. PPI prescription pertinence, mainly using the oral route, was based upon the presence of clearly identified risk factors. PPI mensual consumption and severe gastric complications were analyzed and compared with those obtained from the previous year. Ten months after the beginning of the protocol, the pertinence of PPI prescription was analyzed in 20 randomly selected medical records. Data are expressed in defined daily dose (DDD)., Results: After one year, a 35.5% decrease in oral PPI consumption was noted (901 ± 211 before vs 581 ± 235 DDD, after, P<0.05). A similar trend to a decrease in intravenous PPI consumption was observed (40 ± 23 vs 22 ± 26, P=0.06). During the same period, the overall incidence of severe gastric complication remained stable. The PPI prescription was pertinent in 85% of selected medical records., Conclusion: This study confirmed the interest of professional practice evaluation protocols to improve PPI prescription. A strong implication of all medical staff members is mandatory to maintain such benefits over time., (Copyright © 2011 Elsevier Masson SAS. All rights reserved.)

The paper deals with the links between physiological measurements and cognitive and emotional functioning. As long as the operator is a key agent in charge of complex systems, the definition of metrics able to predict his performance is a great challenge. The measurement of the physiological state is a very promising way but a very acute comprehension is required; in particular few studies compare autonomous nervous system reactivity according to specific cognitive processes during task performance and task related psychological stress is often ignored. We compared physiological parameters recorded on 24 healthy subjects facing two neuropsychological tasks: a dynamic task that require problem solving in a world that continually evolves over time and a logical task representative of cognitive processes performed by operators facing everyday problem solving. Results showed that the mean pupil diameter change was higher during the dynamic task; conversely, the heart rate was more elevated during the logical task. Finally, the systolic blood pressure seemed to be strongly sensitive to psychological stress. A better taking into account of the precise influence of a given cognitive activity and both workload and related task-induced psychological stress during task performance is a promising way to better monitor operators in complex working situations to detect mental overload or pejorative stress factor of error.

Introduction: Drug-induced neuropathies are mainly sensory and subacute. The pathophysiological mechanisms associated with them are not clearly established and few pharmacoepidemiologic studies are available., Method: This study investigated spontaneous reports of peripheral neuropathies reported to the French Adverse Drug Reaction (pharmacovigilance) database over a ten-year period., Results: Between January 1995 and April 2005, 1110 cases were reported, predominantly among men (60%). Patients' mean age was 53.6 years. Most of these reports concerned sensory neuropathies, and 538 (48%) cases were considered "serious". Neuropathies related to dermatologic drugs (mainly retinoids) were serious in 85.7% of cases. Reactions were tentatively attributed to the following pharmacological classes, in decreasing order: antiviral and antibacterial (43.6%), antineoplastic and immunosuppressant (15.9%), cardiovascular (15.9%), central nervous system (7.9%) and gastrointestinal and metabolism (4.8%) agents. Specific drugs suspected of causing neuropathies were stavudine (198 cases), didanosine (134), lamivudine (124), thalidomide (57), ritonavir (55), zalcitabine (53) and amiodarone (47). This study allowed us to consider whether 2 other drugs (allopurinol and flecainide acetate) might be related to the occurrence of neuropathies., Discussion: This work points out the usefulness of spontaneous reports of adverse drug reactions to regional adverse drug reaction reporting centers to help determine the relative frequency of suspected reactions to different drugs and to help detect drugs not previously known to induce these reactions.

The family of alpha(2)-adrenergic receptors (alpha(2)-ARs) comprises three subtypes which are each endowed with specific functions. alpha(2)-agonists and alpha(2)-antagonists are part of the clinician armamentarium since several decades; however, none of the compounds so far available is subtype selective. For long, clonidine and yohimbine have been used for the treatment of hypertension and impotence respectively, but both have been superseded by newer drugs. This review attempts, by a comprehensive analysis of the literature, to cover the present clinical use and the potential therapeutic interest of alpha(2)-agonists or antagonists. From the clinical data, it is concluded that, with the exception of a few particular situations, alpha(2)-agonists are only of limited utility as a monotherapy. By contrast, they offer several powerful advantages when used in adjunctive therapy. In perioperative settings, alpha(2)-agonists are extremely valuable adjuncts to anesthetics and analgesics for the induction of anxiolysis, maintenance of sedation, management of pain and prevention of shivering. In the ophthalmic clinic, they are used to lower intra-ocular pressure during laser surgery of the eye. As a daily medication, alpha(2)-agonists are also of interest for the treatment of glaucoma, muscle spasticity, opiate withdrawal, and behavior disorders. The alpha(2)-antagonists are useful antidotes for reversing the threatening effects of agonist overdose, but currently there are very few indications. New applications are under investigation, and new molecules with more refined subtype-selectivity may emerge, so the clinical utility of both alpha(2)-agonists and antagonists will undoubtedly expand in the future.

Introduction: A national survey has been conducted with 349 general practitioners in order to analyze the management of concerned episodic headache in general practice., Method: This survey enabled collection of data from 2537 headache patients. The main data concered IHS diagnosis, severity of headache using the MIGSEV scale, management, practices and the impact on daily living (QVM and HIT-6 scales)., Results: Out of the 2537 included patients, 52 percent were migraine sufferers according to IHS criteria (code 1.1/1.2), 34 percent presented with migrainous disorders (code 1.7), and 14 percent were non-migraine headache patients. The distribution of management practices showed that 71 percent of them were given non-specific treatments, 46 percent of them specific treatments and 27 percent of them prophylactic treatments. Analysis of the impact of headache using the QVM or the HIT-6 demonstrated a relationship between diagnosis, migraine severity and disability. Analysis of the correlation between the severity of the last migraine attack as evaluated by the patient and that estimated by the doctor showed that the practitioner tended to underestimate the patient's pain. These results highlight the importance of communication between practitioners and migraine sufferers., Conclusion: Training of general practitioners in the use of simple tools such as the HIT-6 scale, should be helpful for a better evaluation of the impact of headache on daily living, and hence should lead to more optimal therapeutic management of headache patients.

Introduction: The aim of this study was to determine whether impaired adaptation of the QT interval to changes in heart rate predicts sudden death in patients with chronic heart failure (CHF)., Methods: We prospectively included 175 CHF patients in sinus rhythm. QT dynamicity was evaluated by analyzing 24-h Holter recordings. The linear regression slope of QT interval measured to the apex and to the end of T wave plotted against RR intervals was calculated using a dedicated Holter algorithm., Results: Mean follow-up was 29.9+/-17.9 months. There were 48 deaths, of which 21 were sudden. The actuarial 3-year mortality rates were 38.4% for overall mortality and 14.1% for sudden death. Of all the parameters, an increased QTe/RR slope (>0.28) was the strongest independent predictor of sudden death (relative risk 3.47, 95% confidence interval 1.43-8.40, p=0.006)., Conclusion: Increased 24-h QTe dynamicity is independently predictive of sudden death among patients with heart failure. This simple parameter may help to stratify risk and select patients who may benefit from antiarrhythmic prophylaxis.

This French pharmacoepidemiological study describes triptan use in general practice for triptan 'naive' (never treated by a triptan before study inclusion) and 'non-naive' (already treated by a triptan) patients. Data from 1774 patients were analysed (81% women). The mean age of the patients was 41 years (+/-12.8). This study showed that 95% of the patients had a diagnosis of migraine according to the International Headache Society (IHS) criteria. This result confirmed the effective use of triptans by general practitioners. Migraines in patients treated with triptans in the present study were more severe than in subjects reporting migraine in the general population. 'Naive' and 'non-naive' patients had similar IHS diagnoses and severity profiles but, for 'non-naive' patients, the migraine history was longer and the disability (quality of life) reported was worse than for the 'naive' patients. The reasons for the treatment switch were the need for improved efficacy, a faster onset of action, fewer recurrences and better tolerability.

Objective: To determine the effect of an alpha2-adrenoceptor antagonist, idazoxan, on the sympathetic nervous system and on energy expenditure responses after an oral glucose load, in obese patients. (idazoxan acts as an indirect sympathomimetic drug through blockade of presynaptic alpha2-adrenoceptors)., Design: Double-blind randomized placebo-controlled cross-over study. Idazoxan (40 mg) or placebo were administered orally 90 min before a 100 g oral glucose load., Subjects: Twelve long-standing obese subjects (six men and six women, age range from 24 to 45 y, body mass index range from 30.2 to 41.3 kg/m2)., Measurements: Energy expenditure was derived from oxygen consumption and carbon dioxide production according to indirect calorimetry. Plasma samples were obtained for plasma adrenaline and noradrenaline, glucose, non-esterified fatty acid (NEFA), glycerol and insulin determinations., Results: The plasma noradrenaline concentration response to the glucose load was significantly higher after idazoxan than after placebo administration. The time-course of glucose load-induced thermogenesis was not significantly different after administration of idazoxan nor placebo. Idazoxan administration did not modify the insulin, non-esterified fatty acids or glycerol concentration responses to the glucose load. Neither heart rate nor blood pressure values were modified by idazoxan when compared to placebo. However, idazoxan significantly improved glucose tolerance., Conclusion: The alpha2-adrenergic antagonist idazoxan increases glucose-induced sympathetic activity but not energy expenditure in obese subjects. These data do not argue for the development of alpha2AR antagonist compounds as anti-obesity treatment.

The 5HTI receptor antagonists currently used for the treatment of migraine headache all belong to the "triptan" group of drugs and have a chemical formula derived from serotonin. This structural similarity explains in part the MAO-A metabolism of certain triptan drugs used in human medicine. Chemical substitutions explain the variable role of different cytochrome P450 isoenzymes and differences in terms of drug interactions. Beyond the analysis of clinical trials, the pharmacologist must examine the epidemiological data on triptans. Prescription studies show an erroneously frequent use of sumatriptan for non-migraine headache. A low percentage of patients consume a large proportion of the sumatriptan prescribed and could be considered as "drug abusers". Epidemiological observation provides better knowledge of adverse effects and a better statistical definition of risk. The high cost of triptans, compared with older drugs, suggests the need to examine the pharmacoeconomical aspects of the question. Much more costly than ergot derivatives, triptans have a favorable cost-benefit and cost-usefulness ratio as is demonstrated by the reduction in loss of productivity, improved quality of life, and cost effectiveness studies.

Physical exercise is a treatment for cardiac failure but a large range of intensities of exercise is proposed. The aims of this study were to determine the range of intensities of effort used and to individualize the intensities used. Thirty patients with stable cardiac failure (NYHA Classes II-III, age: 53 +/- 2.1 years, ejection fraction: 31 +/- 1.4%) underwent a cardiorespiratory exercise stress test before and after individualized training at the ventilatory threshold. However, before and after the training period, standard methods of calculation of the intensities at the ventilatory threshold showed individual differences greater than +/- 2 standard deviations, indicating different metabolic stimulations. After the individualized training programme, peak oxygen consumption on exercise (1679 +/- 100 vs 1487 +/- 89 ml.min-1, p = 0.0001) and at ventilatory threshold increased (1365 +/- 85 vs 1133 +/- 65 ml.min-1, p = 0.0001), the ventilatory threshold/peak exercise ratio increased (81.2 +/- 1.3 vs 76.7 +/- 1.4%, p = 0.0008), and there was a decrease in heart and ventilatory rates at submaximal metabolic levels (p = 0.0001). The authors conclude that protocols using intensity of effort at the ventilatory threshold give similar results with respect to improvement of aerobic capacity as other methods of indirect calculation, based on maximal heart rate of oxygen consumption. The value of this particular method lies in the adequation between aerobic capacity of the patient and the intensity of training. The results obtained attain the physiopathological aims of rehabilitation.

Objective: To assess cardiac beta-adrenoceptors (beta-AR) in an obesity-hypertension model., Methods: Six male beagle dogs (aged 35 +/- 5 months) receiving during 30 weeks a high-fat diet with 60% uncooked beef fat were compared to 6 normal beagle dogs. With right auricular and left ventricular samples we analysed cardiac beta-AR density through binding study using [125I]-cyanopindolol. beta 1 and beta 2 densities were obtained by competition with CGP 20712A. Affinity state of beta-AR was assessed by competition with isoproterenol. Noradrenaline plasma level was assayed by HPLC. Left ventricular mass (LV mass) was measured by echocardiography. Results are expressed as mean +/- SE. All comparisons were performed using a variance analysis (*: p < 0.05)., Results: Systolic blood pressure was significantly higher in obesses (245 +/- 8 vs 197 +/- 10 mmHg in controls). Diastolic blood pressure did not differed between both groups (93 +/- 3 vs 84 +/- 3 mmHg in controls). Noradrenaline plasma levels were similar in both groups (276 +/- 30 vs 235 +/- 50 pg/mL in controls). Obesses were characterized by higher LV mass (80 +/- 24 vs 67 +/- 15 g in controls*). Right auricular and left ventricular beta-AR densities were not different in obesses (57 +/- 6 and 67 +/- 4 fmoles/mg protein) and in controls (68 +/- 7 and 63 +/- 9 fmoles/mg protein). The beta 1-AR proportion was the same in obesses and controls in right auricule (63 +/- 4 vs 64 +/- 3% in controls) and left ventricule (59 +/- 3 vs 60 +/- 4% in controls). The proportion of beta-AR receptors in a high affinity state was similar in right auricular samples (69 +/- 4 vs 67 +/- 3%) in controls) but was significantly different in left ventricule (28 +/- 6 vs 74 +/- 6%) in controls)., Conclusion: Left ventricular beta-adrenoceptors came under a specific desensibilisation independent of plasma noradrenaline levels. This functional decoupling of beta-adrenoceptors may account for the progressive systolic dysfunction of hypertensive cardiomyopathy.

Since the discovery of imipramine by Kübn in 1958, several hypotheses have been developed in order to explain the antidepressant properties of thymoanaleptic drugs. These hypotheses have successively used the results of predictive psychopharmacology, biological psychiatry and more recently biochemistry of depression. These data have led to the discovery of new products with clear antidepressant properties but with a stereotyped 'mono' aminergic mechanism of action. Among these drugs, the currently most prolific family is the group of 'selective' serotonin reuptake inhibitors (SSRI). This review discusses the mechanism of action of the recently marketed antidepressant drugs, their selectivity, drug-induced changes in the synaptic cleft after short and long term treatment, the differences in pharmacodynamics, pharmacokinetics, pharmacogenetics and drug surveillance between the different agents as well as the perspective for the development of new antidepressants.

The synthetic somatostatin analogue, octreotide, has recently been proposed for the treatment of both postprandial and orthostatic hypotension (OH) in humans with autonomic failure related to multiple system atrophy (MSA) or diabetes mellitus. However, pharmacodynamic data are not still available in experimental models of orthostatic hypotension. We investigated in a model of neurogenic orthostatic hypotension, obtained by chronic sinoaortic denervation (SAD) in chloralose-anaesthetized dogs, the effects of octreotide (0.1 mg/kg, subcutaneous route) during a double-blind cross-over study vs placebo. Blood pressure (BP) and heart rate (HR) average values, SBP and HR short-term variabilities (using fast Fourier transformation) in both low (LF: 50-150 mHz) and high frequency range (respiratory rate +/- 50 mHz) and plasma noradrenaline (NA) levels (HPLC) were measured in supine position and during head-up tilt test (HUT: 80 degrees, 10 min) before and 45 min after drug administration. In controls, as expected, head-up tilt test induced a significant increase in DBP (+14 +/- 8 mmHg), HR (+36 +/- 21 beat/min), NA (296 +/- 118 vs 141 +/- 63 pg/ml), SBP-LF (25 +/- 5 vs 14 +/- 3%) whereas HR-HF significantly decreased. The changes during head-up tilt test were not modified after placebo or octreotide administration. In SAD dogs, head-up tilt test elicited a dramatic fall in SBP (-74 +/- 39 mmHg), DBP (-20 +/- 15 mmHg) without any significant change in HR (-5 +/- 12 beat/min), NA (708 +/- 213 vs 606 +/- 331 pg/ml), SBP-LF (16 +/- 3 vs 16 +/- 3%), HR-HF (8 +/- 2 vs 7 +/- 1%). Octreotide or placebo failed to significantly modify any of the measured parameters during head-up tilt test performed 45 min after drug administration. At the dose used, octreotide elicited a 80% decrease in insulin plasma levels after 45 min in both normal and SAD dogs. These results suggest that 1) this experimental model of orthostatic hypotension in SAD dogs is reproductible and can be used to investigate the pharmacological effects of antihypotensive drugs, 2) cardiovascular and biochemical characteristics of the SAD model are similar to those observed in MSA and 3) octreotide, in these experimental conditions, is not able to correct the BP fall during head-up tilt test.

Obesity, hypertension and hyperinsulinism are frequently related and constitute morbid elements of human athero-thrombogenic syndrom. To elucidate physiopathologic mechanisms linking these symptoms, we have developped an experimental model reproducing the morbid triptyque: obesity-hypertension-insulin resistance were induced by hyperlipidic hypercaloric diet. The aim of this study was to investigate cardiovascular modifications elicited by high fat diet. Four male Beagle-Harrier dogs were used in this preliminary study. We investigated before and 7 weeks after the beginning of the hypercaloric hyperlipidic diet morphologic measures, systemic blood pressure (BP) and heart rate (HR), pulmonary blood pressure, cardiac output (CO), systolic ejection volume (SEV), peripheral arterial resistance (PAR) and HR variability on 24 hours' electrocardiogram obtained by Holter method. Echocardiographic modifications of left ventricule was also studied after 20 weeks. Body weight increased (+15.4%) after 7 weeks and remained stable the whole experimental period. This gain was associated with an increase of thoracic and abdominal circonferences (respectively +5.9% and 14.3% at the 7th week). The abdominal increase was significantly more elevated than the thoracic one. This abdominal obesity was associated with an increase in diastolic (+17.9%) and mean (+16.4%) (but not systolic) BP. High fat diet failed to modify arterial pulmonary blood pressures but induced an increase in both CO (3.0 +/- 5.2 vs 4.3 +/- 0.4 ml/min) and SEV (32.4 +/- 5.2 vs 40.8 +/- 2.7 ml/beat). PAR decreased (43.1 +/- 5.9 vs 33.0 +/- 3.2 UW; p = 0.08). Holter method showed a non significant increase of HR (82.0 +/- 7.8 vs 99.5 +/- 5.6 beat/min; p = 0.1) explained by a significant decrease of parasympathetic HR variability (PNN50: 53.5 +/- 4.1 vs 40.9 +/- 4.1%). No echocardiographic modification of left ventricule was found after 20 weeks of high fat diet. This preliminary study shows that, like in humans, high fat diet in dogs induced abdominal obesity with systemic hypertension but failed to provoke left cardiovascular hypertrophy after 20 weeks. This model will allow to characterize the links between cardiovascular and endocrinometabolic alterations occurring during the development of obesity and hypertension.

The effects of levodopa on autonomic nervous system (ANS) were investigated through the measurement of blood pressure (BP) and heart rate (HR) variability in 15 de novo parkinsonian who never received dopaminergic drugs. BP and HR were obtained using digital photoplethysmography in supine and standing positions. Measurements were achieved 90 min after administration, in a double blind cross-over way, of placebo or levodopa (200 mg)+benserazide (50 mg). Spectral analysis was performed using fast Fourier transformation (FFT) on 512 consecutive SBP and HR values. Spectral modulus was integrated for calculation of total spectra and of low frequency (LF: 66-129 mHz) or high frequency band (HF: respiratory frequency +/- 50 mHz). After placebo, orthostatism was followed by a significant increase in BP and HR whereas relative variabilities in LF and HF remained unchanged. After levodopa, BP was significantly lower in supine position without changes in HR and LF. During orthostatism, changes observed in BP and in FFT were similar to those observed during placebo period. These data indicate that levodopa reduces supine and standing BP but does not impair orthostatic adaptation. This effect is not due to modification of BP or HR variability and appears to independent of any direct effect on ANS.

The effect of left ventricular hypertrophy (LVH) due to chronic pressure overload on right atrial (RA) and left ventricular (LV) myocardial beta-adrenergic receptor (beta-AR) density and subtypes, adenylyl cyclase (AC) activity and ADP-pertussis toxin ribosylated proteins was investigated in humans with LVH due to aortic stenosis and in patients without LVH undergoing heart surgery for mitral stenosis or coronary artery disease taken as controls. Both groups presented normal systolic function or plasma catecholamine levels. In LVH and controls, beta-AR density was similar in RA (62 +/- 6 vs 77 +/- 12 fmol.mg-1 protein) and LV (39 +/- 7 vs 32 +/- 2 fmol.mg-1 protein). In LVH, beta 1-AR percentage was < than in controls in LV (35 +/- 11 vs 73 +/- 5%, P < 0.05) but not in RA (79 +/- 5 vs 73 +/- 8%). Basal AC activity in RA (19 +/- 4 vs 21 +/- 6 pmol.mg-1 protein) and LV (22 +/- 5 vs 27 +/- 3 pmol.mg-1 protein) was similar in LVH and in controls. Isoprenaline-induced stimulation of AC in RA was similar in LVH and in controls (51 +/- 18 vs 36 +/- 18%) but < in LV of LVH (7 +/- 6 vs 45 +/- 6%, P < 0.05). In the presence of ICI-118,551 (a beta 2-adrenoceptor antagonist), isoprenaline failed to induce any increase in cAMP in LVH. The quantification of ADP-pertussis toxin ribosylated proteins indicated a lower concentration of substrates in LV myocardial membranes from LVH. These data indicate that in LVH due to pressure overload, there is a down-regulation of beta 1-AR and an increase in beta 2-AR density. This is associated with alterations of the transmembrane signalling marked by a decreased capacity of isoprenaline to stimulate AC and an impaired expression of Gi proteins.