The arterial baroreflex buffers slow (<0.05 Hz) blood pressure (BP) fluctuations, mainly by controlling peripheral resistance. Baroreflex sensitivity (BRS), an important characteristic of baroreflex control, is often noninvasively assessed by relating heart rate (HR) fluctuations to BP fluctuations; more specifically, spectral BRS assessment techniques focus on the BP-to-HR transfer function ar...

The sensitivity of baroreflex control of sympathetic nerve activity (SNA) represents the responsiveness of SNA to changes in blood pressure. In a slightly different analysis, the baroreflex threshold measures the probability of whether a sympathetic burst will occur at a given diastolic blood pressure. We hypothesized that baroreflex threshold analysis could be used to estimate the sensitivity ...

We evaluated a method of baroreflex testing involving sequential intravenous bolus injections of nitroprusside followed by phenylephrine and phenylephrine followed by nitroprusside in 18 healthy men and women, and we drew inferences regarding human sympathetic and vagal baroreflex mechanisms. We recorded the electrocardiogram, photoplethysmographic finger arterial pressure, and peroneal nerve m...

Little is known about baroreflex control of renal nerve sympathetic activity (RSNA) or the effect of angiotensin II (ANG II) on the baroreflex in diabetes. We examined baroreflex control of RSNA and heart rate (HR) in conscious, chronically instrumented rats 2 wk after citrate vehicle (normal) or 55 mg/kg iv streptozotocin (diabetic) before and after losartan (5 mg/kg iv) or enalapril (2.5 mg/k...

Previous studies have demonstrated that the lateral parabrachial nucleus (LPBN) is an important site for descending modulation of baroreflex control of heart rate. In the present study it was hypothesized that the LPBN neurons may also modulate baroreflex control of arterial pressure and sympathetic nerve activity. In urethan-anesthetized rats, electrical or chemical activation of the LPBN prod...

The neural interaction between the cardiopulmonary and arterial baroreflex may be critical for the regulation of blood pressure during orthostatic stress. However, studies have reported conflicting results: some indicate increases and others decreases in cardiac baroreflex sensitivity (i.e., gain) with cardiopulmonary unloading. Thus the effect of orthostatic stress-induced central hypovolemia ...

The role of baroreflexes in long-term control of arterial pressure is unresolved. To determine whether chronic activation of the baroreflex produces sustained hypotension, we developed a method for prolonged activation of the carotid baroreflex in conscious dogs. This was achieved by chronically implanting electrodes around both carotid sinuses and using an externally adjustable pulse generator...

Insulin resistance confers risk for diabetes mellitus and associates with a reduced capacity of the arterial baroreflex to regulate blood pressure. Importantly, several brain regions that comprise the central autonomic network, which controls the baroreflex, are also sensitive to the neuromodulatory effects of insulin. However, it is unknown whether peripheral insulin resistance relates to acti...

Patients with hypertension have a blunted sensitivity of baroreflex control of heart period. In these patients, baroreflex sensitivity is positively related to heart rate variability and inversely related to blood pressure variability. We hypothesized that this relationship would also be evident in healthy normotensive subjects and that individuals with higher baroreflex sensitivity would have ...

In early studies of humans, baroreflex sensitivity was found to be higher during sleep; however, subsequent observations in several species, including humans, have been at variance with the original reports. Sleep and arousal are behavioral states, and it is difficult to accurately and repeatedly measure baroreflex sensitivity in behaving animals. However, pharmacologically immobilized (neuromu...