Autonomic blockade and the Valsalva maneuver in patients on maintenance hemodialysis: a hemodynamic study.

Hemodynamic studies were performed at two levels of dietary sodium intake (10 mmoles/day and 100 mmoles/day for 14 days) in a group of patients (with retained kidneys) on chronic hemodialysis. Plasma renin activity and aldosterone, plasma, and extracellular fluid (ECF) volumes were measured while the patient were at rest. Cardiac output, mean intraarterial pressure, and the calculated total peripheral resistance index were recorded while the patients were at rest and during acute "total" autonomic blockade.

Regional vascular resistance and heart rate responses mediated through H1- and H2-histamine receptors in the unanaesthetised rabbit.

The effects of histamine infusions (10-100 microgram/kg/min) on heart rate and hindlimb, carotid, mesenteric and renal vascular resistance were investigated in unanaesthetised rabbits after "total" autonomic effector block to abolish reflex effects. Histamine caused a rise in heart rate that was predominately due to stimulation of H2-receptors (blocked by metiamide). Hindlimb and carotid vascular resistance did not change significantly during histamine infusion.

Leakage of dl-propranolol from cerebrospinal fluid to the bloodstream in the rabbit.

Intracerebroventricular (i.c.v.

Baroreflex "resetting" by arterial hypoxia in the renal and cardiac sympathetic nerves of the rabbit.

1. Renal and cardiac sympathetic baroreflex functions were studied in sodium pentobarbitone anaesthetized rabbits given succinylcholine, during constant artificial ventilation with air and with hypoxic gas mixtures. Mean arterial pressure (MAP) was raised and lowered between values of 40 and 140 mm Hg by means of aortic and vena caval periovascular balloons and integrated sympathetic nerve activity (SNA) was recordered.

Effects of histamine bolus injections and continuous infusions on the H1- and H2-receptors in the hindlimb vessels of the rabbit.

1. Hindlimb vascular resistance (HVR) was continuously measured after pharmacological block of the autonomic effectors in unanesthetized rabbits with previously implanted Doppler ultrasonic flowmeters. 2.

Assessment of autonomic and non-autonomic components of resting hindlimb vascular resistance and reactivity to pressor substances in renal hypertensive rabbits.

1. Hindlimb vascular resistance (HVR) was measured before and after pharmacological autonomic blockade in unanesthetized renal cellophan-wrap hypertensive or normotensive rabbits with previously implanted Doppler ultrasonic flowmeters. 2.

Cardiac output changes during experimental renal hypertension in the rabbit.

1. The haemodynamic changes during the development of hypertension in rabbits have been studied for 1 week before and 4-5 weeks after sham-operation (thirteen rabbits) or bilateral renal cellophan wrapping (thirteen rabbits), Doppler flowmeters being used to measure cardiac output. 2.

Quantitative effects of timolol and hydrochlorothiazide on blood pressure, heart rate and plasma renin activity: results of a double-blind factorial trial in patients with essential hypertension.

1. The anti-hypertensive actions of timolol and hydrochlorothiazide were analysed in a double-blind 2 x 2 factorial trial in twenty patients with essential hypertension. Each patient went through four phases of 8 weeks in randomized order, receiving timolol alone, hydrochlorothiazide alone, timolol plus hydrochlorothiazide, and placebo.

Valsalva vasoconstrictor reflex in human hypertension in after beta-adrenoreceptor blockade in conscious rabbits.

1. A Valsalva-like manoeuvre was used to elicit graded rises in total peripheral resistance (TPR) in conscious rabbits. The rises were reflex and mediated through sympathetic constrictors.

Changes in cardiac output and total peripheral resistance during development of renal hypertension in the rabbit: lack of confomity with the autoregulation theory.

Serial measurements of cardiac output (CO), mean arterial pressure (MAP), heart rate, and total peripheral resistance (TPR), were made on unanesthetized rabbits with previously implanted Doppler flowmeters. After 2 days of control measurements the rabbits were subjected alternatively to bilateral renal cellophane wrapping (wrap group) or to sham operation and additional measurements were made 1, 2, 4, 8, 16, 25, and 32 days after operation. During the 1st week after operation changes in CO were identical in the wrap and sham-operated groups, with an overall increase to a value of 110% of control on day 4 (P less than 0.

Effect of beta-adrenergic blockade with alprenolol on ST-segment depression and circulatory dynamics during exercise in patients with effort angina.

1. Nine subjects with severe coronary artery disease were studied during graded "sprint" and "steady-state" exercise before and after intravenous administration of the beta-receptor antagonist alprenolol. During "sprint" workload was increased every minute until maximum work capacity (Wmax) was reached.

Double-blind factorial trial of prindolol and hydrochlorothiazide in hypertension.

The antihypertensive actions of the beta-adrenergic blocking agent, prindolol, and of the diuretic, hydrochlorothiazide, were analysed in a double-blind randomized 2 X 2 factorial trial in 16 patients. There were four eight-week phases in which patients received prindolol alone, hydrochlorothiazide alone, prindolol plus hydrochlorothiazide in combination, and no treatment. Both drugs were given in fixed doses: prindolol, 10 mg three times per day; hydrochlorothiazide, 50 mg per day.

Reflex and mechanical circulatory effects of graded Valsalva maneuvers in normal man.

In 17 normal subjects we studied the changes evoked by five levels of expiratory pressure (EP) ranging from 2.5 to 30 mmHg in a number of circulatory variables during the last 10 s of a 30-s Valsalva maneuver. Variables studied included mean arterial (MAP) and pulse (PP) pressures; right atrial (RAP) and peripheral vein (PVP) pressures; cardiac output (CO); total peripheral resistance (TPR) and heart rate (HR).

Action of propranolol on arterial pressure and on cardiovascular reflexes.

In the rabbit, administration of 500 mug (+/-) propranolol into the lateral cerebral ventricle resulted in rapid leakage of drug into the blood. The drug produced a small reduction in blood pressure at 2 and 4 hours after injection but because of the rapid leakage, this could have been due to its peripheral actions. To investigate possible central mechanisms of action which were independent of peripheral effects, we tested the action of intravenously administered propranolol on the reflex rise in TPR evoked in rabbits by graded Valsalva-like manoeuvres.

Estimation of non-autonomic and autonomic components of iliac bed vascular resistance in renal hypertensive rabbits.

Iliac bed vascular resistance (IVR) was measured before and after pharmacological block of the autonomic effectors in unanaesthetized renal hypertensive and normotensive rabbits with previously implanted Doppler flowmeters. This permitted partitioning the resting IVR into a non-autonomic component (ie, steady-state IVR after block) and an autonomic component (ie, resting IVR minus non-autonomic IVR). When IVR was measured at the same mean arterial pressure (MAP) before and after block in each animal, the increase in estimated non-autonomic IVR accounted entirely for the rise in resting IVR in renal hypertensive rabbits.

The action of clonidine on the baroreflex control of heart rate in conscious animals and man, and on single aortic baroreceptor discharge in the rabbit.

Changes in mean arterial pressure (M.A.P.

Central nervous system control of cardiorespiratory nasopharyngeal reflexes in the rabbit.

The role of different central nervous regions in the reflex apnea, bradycardia, and mesenteric vasoconstriction evoked by nasopharyngeal stimulation with cigarette smoke was examined in unanesthetized shamoperated, thalamic, and pontine rabbits with intact and sectioned carotid sinus and aortic nerves (CS and AN). Apnea occurred in all preparations. In pontine animals with intact CS and AN, the heart rate response was reduced but not the mesenteric vasoconstriction.