We used Daphnia magna bioassays to determine the LC(50) and the effects on the heart of the cardioactive drugs ouabain, verapamil, metaproterenol and metoprolol. Distinctions were made between the pharmacological and toxicological effects of these drugs and the adequacy of physicochemical characteristics of its habitat (reconstituted water). Video microscopy and digital image processing were us...

The aim of this study was to assess the influence of atrial natriuretic factor (ANF) on arterial baroreflex chronotropic responses and to investigate whether this effect of ANF is affected by angiotensin converting enzyme inhibition (CEI). For this purpose, in 13 normal volunteers, the reflex chronotropic responses to arterial baroreceptor stimulation (phenylephrine, 25-100 micrograms i.v.) or ...

Etiology of the negative chronotropic response to coronary artery occlusion was studied in chloralose-anesthetized monkeys. One-minute occlusion of the circumflex (CIRC) coronary artery resulted in marked negative chronotropic responses and consistent alterations in atrial electrograms. These responses were dependent on interruption of flow to a small proximal CIRC branch, and postmortem examin...

CHIBA, S. Potentiation of the Negative Chronotropic and Isotropic Effects of Adenosine by Dipyridamole. Tohoku J. exp. Med ., 1974, 114 (1), 45-48 The isolated right atrium of the dog was perfused with blood led from a support dog. The selective injection of dipyridamole into the sinus node artery at a dose of 1-10 ƒÊg induced a slight negative chronotropic and positive inotropic effect. The ad...

The effects of infusions of cocaine (COC) and metanephrine (MET) on the inotropic and chronotropic responses to cardiac sympathetic nerve stimulation were studied in open-chest, anesthetized dogs. COC blocks the neuronal uptake of norepinephrine (NE), whereas MET blocks the extraneuronal uptake. Both blocking agents slightly enhanced the inotropic but not the chronotropic responses. COC prolong...

  The effect of different doses (1-50 µ M) of imipramine (IMI) and desipramine (DES) on the rate and force of contraction of isolated rat atria was studied. IMI and DES produced a dose-dependent increase in force of contraction (31- 94% for IMI and 35-118% for DES). Pretreatment of rats with reserpine (5 mg/kg) on the isolated atria with propranolol (1 µ g) inhibited the positive ionotropic eff...

PURPOSE Metabolic-chronotropic relationship is the only concept that assesses the entire chronotropic function during exercise, as it takes into account individual fitness. To better understand interrelationships between chronotropic incompetence (CI), dynamic hyperinflation (DH) and exercise limitation among Global initiative for chronic Obstructive Lung Disease (GOLD) stages of chronic obstru...

Cardiac tissue is densely innervated by sensory neurons that are believed to play important modulatory roles in cardiac functions. In this study, pretreatment of neonate rats with capsaicin was performed. In adult rats, cardiomyocyte size and amount of fibrous tissue in left ventricles as well as in vitro coronary flow were evaluated. The chronotropic and inotropic responses to beta-adrenocepto...

Letter by Prakash Regarding Article “Impaired Heart Rate Recovery and Chronotropic Incompetence in Patients With Heart Failure With Preserved Ejection Fraction” To the Editor: This study by Phan et al1 provides evidence of chronotropic incompetence in patients with heart failure but preserved left ventricular ejection fraction. The authors discuss autonomic dysregulation of the sinoatrial node ...

The aim of this study was to assess the influence of atrial natriuretic factor (ANF) on arterial baroreflex chronotropic responses and to investigate whether this effect of ANF is affected by angiotensin converting enzyme inhibition (CEI). For this purpose, in 13 normal volunteers, the reflex chronotropic responses to arterial baroreceptor stimulation (phenylephrine, 25-100 jig i.v.) or deactiv...