Pharmacological examinations of isolated auricles from Sepia officinalis were carried out to analyze the putative role of the monoaminergic transmitter/receptor system in the control of auricle function. In conjunction with histofluorescence studies and HPLC analyses, evidence of a double excitatory serotonergic and noradrenergic innervation of the auricles was obtained. Serotonin-induced posit...

Decreased cardiac responsiveness to adrenergic stimulation has been observed in cholestatic liver disease, but the cause remains unclear. Previous reports have suggested that nitric oxide overproduction might have a role in cholestasis-induced bradycardia via inhibition of L-type calcium channels. In the present study, the digoxin has been used to increase cardiac Ca2+ transient in male Sprague...

1. Tse HF, Siu CW, Lee KL, et al. The incremental benefit of rateadaptive pacing on exercise performance during cardiac resynchronization therapy. J Am Coll Cardiol 2005;46:2292–7. 2. Lau CP. Normal exercise cardiopulmonary physiology and chronotropic incompetence. In: Lau CP, editor. Rate Adaptive Cardiac Pacing: Single and Dual Chamber. Mount Kisco, NY: Futura Publishing, 1993:7–23. 3. Fei L,...

BACKGROUND Chronotropic incompetence is defined as the inability to reach 80% of heart rate (HR) reserve or 80% of the maximally predicted HR during exercise. The presence of chronotropic incompetence is associated with reduced peak oxygen consumption, and rate-responsive pacing therapy is under investigation to improve exercise capacity in heart failure (HF). However, uncertainty exists about ...

A decrease in maximal exercise heart rate (HR(max)) is a key contributor to reductions in aerobic exercise capacity with aging. However, the mechanisms involved are incompletely understood. We sought to gain insight into the respective roles of intrinsic heart rate (HR(int)) and chronotropic beta-adrenergic responsiveness in the reductions in HR(max) with aging in healthy adults. HR(max) (Balke...

BACKGROUND An abnormally low chronotropic response and an abnormally high ventilatory response (V(E)/V(CO2)) to exercise are common in patients with severe heart failure, but their relative prognostic impacts have not been well explored. METHODS AND RESULTS Consecutive patients with heart failure referred for metabolic stress testing who were not taking beta-blockers or intravenous inotropes ...

objective: in ventricular arrhythmias, due to their free radical scavenging action, antioxidant agents are usually used in the treatment of cardiovascular disease. since stress is considered as risk factor for increased mortality by causing malignant arrhythmias, the study was designed to evaluate the cardioprotective effects of ellagic acid (ea) on cacl2-induced arrhythmias in rat stress model...

background: there are controversial reports about the exact mechanisms of lead-induced hypertension, but many factors such as alteration in the responsiveness of cardiovascular system to endogenous substances including catecholamines could be one of the mechanisms involved. in present study, the effect of exposure to 100 ppm lead acetate by drinking water (in the periods of 4, 8 and 12 weeks) o...

We studied the time-dependent changes in the response of heart rate (sinus cycle length) to 30-second trains of vagal stimulation (8 Hz), repeated every 2 minutes, in canine neonates aged 7.1 +/- 2.5 (mean +/- SD) days. The first vagal train prolonged the sinus cycle length by 58 +/- 35%, but the response was attenuated during subsequent trains (98 +/- 5% inhibition of the vagal response after ...

Patients with pulmonary arterial hypertension (PAH) exhibit a limited increase in stroke volume on exercise, and the heart rate (HR) increases may reflect the main mechanism that allows cardiac output to increase. The current prospective study documented the contribution of HR to the 6-min walking distance (6MWD) in idiopathic (IPAH) and nonidiopathic PAH. Eighty-three patients (46 IPAH and 37 ...