We tested the hypothesis that acute hypoxia would alter the sensitivity of arterial baroreflex control of both heart rate and sympathetic vasoconstrictor outflow. In 16 healthy, nonsmoking, normotensive subjects (8 women, 8 men, age 20-33 yr), we assessed baroreflex control of heart rate and muscle sympathetic nerve activity by using the modified Oxford technique during both normoxia and hypoxi...

The present experiments investigate whether the absence of tachycardia during lowering of blood pressure (BP) with an angiotensin-converting enzyme inhibitor (CEI) in salt-depleted dogs is due to an alteration in the activity of the baroreflex. Baroreflex activity was measured after pharmacological manipulation of BP using intravenous nitroglycerin or phenylephrine, and the heart period (R-R in...

OBJECTIVE To investigate the effect of estrogen exerted through the autonomic system in the nucleus tractus solitarii (NTS) on increasing the sensitivity of the baroreflex under conditions of acute hypertension in ovariectomized rats. METHODS In this experimental study, conducted in Kerman University of Medical Sciences, Kerman, Iran from March 2010 to October 2010, 36 female rats were ovarie...

1. Baroreflex sensitivity was studied in relation to the development of spontaneous hypertension in rats (SH rats), with normotensive Wistar-Kyoto (WKY) rats as controls. Conscious, freely moving animals were studied at different times, ranging from 4 to 20 weeks after birth. 2. The youngest SH rats (4-6 weeks; n = 10) already had significantly (P less than 0.01) higher mean arterial blood pres...

BACKGROUND Depressed baroreflex sensitivity obtained by means of a phenylephrine test plays a prognostic role in patients with a previous myocardial infarction. Our purpose was to evaluate the correlation and agreement between the baroreflex sensitivity obtained with phenylephrine and that obtained by two noninvasive methods: the alpha-index and sequence analysis. METHODS AND RESULTS The alph...

To investigate the effect of amlodipine on baroreflex sensitivity and sympathetic system activity, 36 patients with essential hypertension were randomized to once-daily, double-blind treatment with amlodipine 5 mg or placebo 5 mg for 60 days. Measurements with a Finapres device allowed calculation of baroreflex sensitivity and blood pressure (BP) variability. Adrenergic activity was assessed vi...

Derangements within autonomic nervous system take part in the natural history of cardiovascular disease. Current paper presents three categories of methods measuring autonomic status: direct methods (e.g. laboratory tests measuring circulating catecholamine levels or based on isotopes, microneurography), indirect methods applied at rest (e.g. analysis of heart rate variability, spectral and seq...

as the millisecond increase in cycle length per mm Hg rise in systolic pressure. The slope is an index of baroreflex sensitivity and was found to have an average value of 12.8 in 18 subjects without hypertension and 2.8 in 12 others with hypertension. When all results were pooled, there was an inverse relationship between the resting mean arterial pressure and slope of the baroreflex regression...

Intra-arterial pressure, baroreflex sensitivity and the baroreflex set point were measured in eight patients with essential hypertension during a control period and then after acute treatment (2 h after a 30 mg oral dose) and after chronic treatment (at least 2 months) with nicardipine hydrochloride, a calcium channel antagonist. Mean intra-arterial blood pressure fell after the acute treatment...

The protection from coronary events that young women have is sharply reduced at menopause. Oxidative stress and baroreflex sensitivity impairment of the circulation have been demonstrated to increase cardiovascular risk. On the other hand, exercise training has been indicated as a nonpharmacological treatment for many diseases. The aim of the present study was to test the hypothesis that exerci...