Cervical vagal stimulation for 2 h results in a depressed baroreflex sensitivity produced by an enhanced sympathetic output, as indicated by increased plasma norepinephrine levels. The current study examined the role of the insular cortex in modulating the vagal stimulation-induced changes in baroreflex sensitivity. Male Sprague-Dawley rats were anesthetized with thiobutabarbitol sodium and ins...

Spontaneous fluctuations in Heart Period (HP) and Mean Arterial Pressure (MAP) make it possible to evaluate baroreceptor-heart rate reflex sensitivity (BRS). 30-s sequences of HP and MAP beat-to-beat values were considered in the different wake-sleep states (Wake, W; Quiet Sleep, QS; Active Sleep, AS) in rats to assess whether 1) BRS changes between states and 2) the different indexes supply co...

1. It is often assumed that the power in the low- (around 0.10 Hz) and high-frequency (around 0.25 Hz) bands obtained by power spectral analysis of cardiovascular variables reflects sympathetic and vagal tone [corrected] respectively. An alternative model attributes the low-frequency band to a resonance in the control system that is produced by the inefficiently slow time constant of the reflex...

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...

Cardiovascular autonomic neuropathy (CAN) is a frequent complication of diabetes mellitus, which is associated with increased morbidity and mortality. It involves both the parasympathetic and sympathetic nervous systems, and may be diagnosed by classical dynamic tests with measurements of heart rate (HR) and/or arterial blood pressure (BP). An original squat test (1-min standing, 1-min squattin...

To determine the short-term effects of noninvasive positive-pressure ventilation (PPV) on spontaneous baroreflex sensitivity, we acquired time series of R-R interval and beat-to-beat blood pressure in 55 healthy volunteers (mean age 46.5 +/- 10.5 yr) who performed breathing on four occasions at frequencies of 12 and 15 breaths/min without positive pressure (control) and also using PPV of 5 mbar...

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...

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...