Autonomic information flow (AIF) characterizes fetal heart rate (FHR) variability (fHRV) in the time scale dependent complexity domain and discriminates sleep states [high voltage/low frequency (HV/LF) and low voltage/high frequency (LV/HF) electrocortical activity (ECoG)]. However, the physiologic relationship of AIF time scales to the underlying sympathetic and vagal rhythms is not known. Und...

OBJECTIVES To study non-linear complexity or chaotic behaviour of heart rate in short time series and its dependence on autonomic tone. METHODS Ten healthy individuals (5 men, mean age 44 years) were investigated at rest, after intravenous injections of propranolol (0.15 mg/kg), followed by atropine (0.03 mg/kg). On another occasion, investigation was made during exercise on a bicycle ergomet...

The relation of renin-angiotensin status to general hemodynamics and to neurogenic vascular resistance was studied in patients with border-line hypertension. Plasma renin activity during standing was referred to a standard renin-urinary sodium nomogram derived from 18 normal subjects. Among 22 patients with borderline hypertension the renin level was high in 8, low in 4 and within normal limits...

OBJECTIVE This study investigated the dominance of each limb of the autonomic nervous system and tested sympathetic-vagal interactions in the human ventricle and atrium after administration of propranolol and atropine. PATIENTS AND METHODS The 90% monophasic action potential duration (MAPD90) and the effective refractory period (ERP) at the right ventricular apex (RV) and the right lateral at...

atropine has been used to block cholinergic neurotransmission in basic research. large doses of atropine cause vasodilation of the blood vessels in the skin. this effect is apparently unconnected with the antimuscarinic activity of atropine and seems to be due to a direct action on the blood vessels. it has been suggested that atropine blocks muscarinic receptors at low doses and it induces the...

Two investigations have been carried out. The first studied the effects of autonomic blockade on the cardiovascular response to a step test, a 50% maximum isometric grip test and a Valsalva manoeuvre: the step test was of 5 minutes duration and the other two for as long as possible. beta adrenergic blockade by propanolol diminished the blood pressure and pulse rate response to both the step tes...

We studied the effects of intracoronary injection of nicotine and acetylcholine on coronary blood flow in nine conscious calves chronically instrumented to measure coronary blood flow, left ventricular (LV) and mean arterial pressure, LV dP/dt, and heart rate. Nicotine (5 micrograms/kg i.c.) elicited a biphasic response in coronary blood flow consisting of an initial vasoconstriction (phase 1; ...

The present study was undertaken to determine the effects of intracoronary administration of the veratrum alkaloid veratridine on coronary blood flow and resistance in conscious, chronically instrumented intact and sinoaortic denervated dogs. Ten dogs were instrumented with a Doppler flow probe on the left anterior descending coronary artery. A chronic catheter was placed in the left circumflex...