Investigating autonomic nervous system dysfunction among patients with post-COVID condition and prolonged cardiovascular symptoms.

Heart Rate Variability (HRV) and arterial pressure (AP) variability and their responses to head-up tilt test (HUTT) were investigated in Post-COVID-19 syndrome (PCS) patients reporting tachycardia and/or postural hypotension. Besides tachycardia, PCS patients also showed attenuation of the following HRV parameters: RMSSD [square root of the mean of the sum of the squares of differences between adjacent normal-to-normal (NN) intervals] from statistical measures; the power of RR (beat-to-beat interval) spectra at HF (high frequency) from the linear method spectral analysis; occurrence of 2UV (two unlike variation) pattern of RR from the nonlinear method symbolic analysis; and the new family of statistics named sample entropy, when compared to control subjects. Basal AP and LF (low frequency) power of systolic AP were similar between PCS patients and control subjects, while 0 V (zero variation) patterns of AP from the nonlinear method symbolic analysis were exacerbated in PCS patients.

Autonomic modulation of arterial pressure and heart rate variability in hypertensive diabetic rats.

Objective: The aim of the present study was to evaluate the autonomic modulation of the cardiovascular system in streptozotocin (STZ)-induced diabetic spontaneously hypertensive rats (SHR), evaluating baroreflex sensitivity and arterial pressure and heart rate variability.

Methods: Male SHR were divided in control (SHR) and diabetic (SHR+DM, 5 days after STZ) groups. Arterial pressure (AP) and baroreflex sensitivity (evaluated by tachycardic and bradycardic responses to changes in AP) were monitored.

Stress cardiovascular/autonomic interactions in mice.

Studies evaluated the role of the autonomic nervous system in the cardiovascular response to stress using radiotelemetric blood pressure (BP) recording coupled with autoregressive spectral analysis. Conscious male C57/BL6 mice with carotid arterial telemetric catheters were exposed to acute episodes of shaker stress before and after administration of cholinergic, beta1-adrenergic and alpha1-adrenergic receptor antagonists. Pulse interval (PI) and systolic arterial pressure (SAP) were analyzed for variance and the low frequency (LF: 0.

Role of nitric oxide and prostanoids in attenuation of rapid baroreceptor resetting.

Because the regulation of vascular function involves complex mutual interactions between nitric oxide (NO) synthase (NOS) and cyclooxygenase (COX) products, we examined the contribution of NO and prostanoids derived from the COX pathway in modulating aortic baroreceptor resetting during an acute (30 min) increase in arterial pressure in anesthetized rats. Increase in pressure was induced either by administration of the nonselective NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) or aortic coarctation (COA) with or without treatment with the COX inhibitor indomethacin (INDO) or the selective neuronal NOS inhibitor 1-(2-trifluoromethylphenyl)imidazole (TRIM). The activity of the aortic depressor nerve and arterial pressure were simultaneously recorded, and the degree of resetting was determined by the shift of the pressure-nerve activity curve using the ratio [delta systolic pressure at 50% of maximum baroreceptor activity/delta systolic pressure] x 100.

Frequency-dependent baroreflex modulation of blood pressure and heart rate variability in conscious mice.

The goal of this study was to determine the baroreflex influence on systolic arterial pressure (SAP) and pulse interval (PI) variability in conscious mice. SAP and PI were measured in C57Bl/6J mice subjected to sinoaortic deafferentation (SAD, n = 21) or sham surgery (n = 20). Average SAP and PI did not differ in SAD or control mice.

Cardiovascular autonomic control in mice lacking angiotensin AT1a receptors.

Studies examined the role of angiotensin (ANG) AT1a receptors in cardiovascular autonomic control by measuring arterial pressure (AP) and heart rate (HR) variability and the effect of autonomic blockade in mice lacking AT1a receptors (AT1a -/-). Using radiotelemetry in conscious AT1a +/+ and AT1a -/- mice, we determined 1) AP and pulse interval (PI) variability in time and frequency (spectral analysis) domains, 2) AP response to alpha(1)-adrenergic and ganglionic blockade, and 3) intrinsic HR after ganglionic blockade. Pulsatile AP was recorded (5 kHz) for measurement of AP and PI and respective variability.

Neurohumoral mechanisms involved in the hypertensive response elicited by bilateral carotid occlusion in conscious intact or chronically sympathectomized rats.

Bilateral carotid occlusion (BCO) increases the sympathetic drive to the circulatory system in conscious intact rats, producing a hypertensive response characterized by two components, i.e., an initial peak followed by a sustained response of lower intensity.

Acute and chronic stress influence blood pressure variability in mice.

There is evidence that alterations in heart rate and blood pressure variability (BPV) are associated with cardiovascular disease. We used a mice model to investigate the effects of acute and chronic stress on blood pressure variability (BPV) and heat rate variability (HRV). Shaker stress was given acutely (5 min, 150 cycles/min) and chronically (3 days, 2 min stress, 150 cycles/min, 45 sessions/day) in male C57BLJ mice.

Enhanced heart rate variability and baroreflex index after stress and cholinesterase inhibition in mice.

Experiments tested the effect of stress coupled with cholinesterase inhibition on blood pressure, heart rate, baroreflex index, and variability in time and frequency domain in conscious mice. The objective was to determine whether cholinergic systems interact with stress to alter cardiovascular responses. Male C57BL/6J mice with arterial catheters were exposed to 3-day treatments: 1) intermittent shaker stress, 2) pyridostigmine (10 mg.