Gestational effects on volume-sensitive cardiopulmonary receptor reflexes in the rat

1995 ◽  
Vol 268 (3) ◽  
pp. R736-R743 ◽  
Author(s):  
T. Hines ◽  
S. W. Mifflin
Keyword(s):  
Sympathetic Nerve Activity ◽  
Right Atrial ◽  
Nerve Activity ◽  
Pregnant Rats ◽  
Renal Sympathetic Nerve Activity ◽  
Cell Discharge ◽  
Afferent Stimulus ◽  
Gallamine Triethiodide ◽  
Renal Sympathetic ◽  
Stimulation Of

We tested the hypothesis that augmented reflex sympathoinhibition mediated by volume-sensitive cardiopulmonary (CP) receptors contributes to the vasodilation of pregnancy by comparing responses to acute volume expansion in 21-day-pregnant and age-matched virgin rats (n = 7) that were anesthetized (pentobarbital sodium, 50 mg/kg ip), paralyzed (gallamine triethiodide, 25 mg/kg iv), ventilated, and had undergone bilateral sinoaortic denervation. CP receptors were stimulated with intra-atrial injections of saline (50, 100, 200, and 300 microliter), and the following variables were recorded: 1) mean right atrial pressure (MRAP) to index the afferent stimulus intensity; 2) cell discharge in the nucleus tractus solitarii (NTS), the primary central terminus for CP afferents; and 3) mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) to assess efferent reflex effects. Basal MAP was significantly lower in pregnant (71.5 +/- 3.8 mmHg) than in virgin rats (86.6 +/- 3.1 mmHg), and plasma volume was expanded in the pregnant group (17.6 +/- 1.1 vs. 10.0 +/- 0.7 ml, P < 0.05). Baseline MRAP was similar between groups. Saline injections evoked graded increases in MRAP, which were larger in gravid animals (P < 0.05). Volume injections evoked similar changes in NTS cell discharge between groups, but the responses were nongraded. Despite larger changes in MRAP in gravid rats, reflex effects on RSNA and HR were similar to those in control animals, and effects on MAP were attenuated in the pregnant group. We conclude that larger changes in MRAP in pregnant rats during stimulation of CP receptors are not associated with larger changes in central or efferent components of this reflex.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Role of the heart in blood pressure lowering during chronic baroreflex activation: insight from an in silico analysis

2018 ◽  
Vol 315 (5) ◽  
pp. H1368-H1382 ◽  
Author(s):  
John S. Clemmer ◽  
W. Andrew Pruett ◽  
Robert L. Hester ◽  
Radu Iliescu ◽  
Thomas E. Lohmeier
Keyword(s):  
Blood Pressure ◽  
Mathematical Model ◽  
Renal Denervation ◽  
Sympathetic Nerve Activity ◽  
Blood Pressure Lowering ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Pressure Lowering ◽  
Renal Sympathetic ◽  
Stimulation Of

Electrical stimulation of the baroreflex chronically suppresses sympathetic activity and arterial pressure and is currently being evaluated for the treatment of resistant hypertension. The antihypertensive effects of baroreflex activation are often attributed to renal sympathoinhibition. However, baroreflex activation also decreases heart rate, and robust blood pressure lowering occurs even after renal denervation. Because controlling renal sympathetic nerve activity (RSNA) and cardiac autonomic activity cannot be achieved experimentally, we used an established mathematical model of human physiology (HumMod) to provide mechanistic insights into their relative and combined contributions to the cardiovascular responses during baroreflex activation. Three-week responses to baroreflex activation closely mimicked experimental observations in dogs including decreases in blood pressure, heart rate, and plasma norepinephrine and increases in plasma atrial natriuretic peptide (ANP), providing validation of the model. Simulations showed that baroreflex-induced alterations in cardiac sympathetic and parasympathetic activity lead to a sustained depression of cardiac function and increased secretion of ANP. Increased ANP and suppression of RSNA both enhanced renal excretory function and accounted for most of the chronic blood pressure lowering during baroreflex activation. However, when suppression of RSNA was blocked, the blood pressure response to baroreflex activation was not appreciably impaired due to inordinate fluid accumulation and further increases in atrial pressure and ANP secretion. These simulations provide a mechanistic understanding of experimental and clinical observations showing that baroreflex activation effectively lowers blood pressure in subjects with previous renal denervation. NEW & NOTEWORTHY Both experimental and clinical studies have shown that the presence of renal nerves is not an obligate requirement for sustained reductions in blood pressure during chronic electrical stimulation of the carotid baroreflex. Simulations using HumMod, a mathematical model of integrative human physiology, indicated that both increased secretion of atrial natriuretic peptide and suppressed renal sympathetic nerve activity play key roles in mediating long-term reductions in blood pressure during chronic baroreflex activation.

scholarly journals Angiotensin receptor antagonist improves cardiac reflex control of renal sodium handling in heart failure

1998 ◽  
Vol 274 (2) ◽  
pp. H636-H641 ◽  
Author(s):  
Gerald F. Dibona ◽  
Susan Y. Jones ◽  
Linda L. Sawin
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Right Atrial ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Renal Sodium Handling ◽  
Renal Sympathetic

In rats with congestive heart failure, type 1 angiotensin II receptor antagonist treatment (losartan) decreases basal renal sympathetic nerve activity and improves arterial baroreflex regulation of renal sympathetic nerve activity. This investigation examined the effect of losartan on cardiac baroreflex regulation of renal sympathetic nerve activity and renal sodium handling in rats with congestive heart failure. Losartan treatment decreased arterial pressure from 120 ± 3 to 93 ± 5 mmHg and increased the afferent (from 0.95 ± 0.21 to 2.22 ± 0.42% Δafferent vagal nerve activity/mmHg mean right atrial pressure, P < 0.05) and overall gain (from −1.14 ± 0.19 to −4.20 ± 0.39% Δrenal sympathetic nerve activity/mmHg mean right atrial pressure, P < 0.05) of the cardiac baroreflex. During isotonic saline volume loading, urinary sodium excretion increased from 2.4 ± 0.8 to 10.5 ± 1.3 μeq/min in vehicle-treated rats (excretion of 52 ± 3% of the load) and from 3.0 ± 1.0 to 15.1 ± 1.8 μeq/min in losartan-treated rats (excretion of 65 ± 4% of the load, P < 0.05). When rats were changed from a low- to a high-sodium diet, cumulative sodium balance over 5 days was 7.8 ± 0.6 meq in vehicle-treated rats and 4.2 ± 0.4 meq in losartan-treated rats ( P < 0.05). In congestive heart failure, losartan treatment improved cardiac baroreflex regulation of renal sympathetic nerve activity, which was associated with improved ability to excrete acute and chronic sodium loads.

Effects of corticospinal tract stimulation on renal sympathetic nerve activity in rats with intact and chronically lesioned spinal cords

2007 ◽  
Vol 293 (1) ◽  
pp. R178-R184 ◽  
Author(s):  
Baohan Pan ◽  
Matthew R. Zahner ◽  
Ewa Kulikowicz ◽  
Lawrence P. Schramm
Keyword(s):  
Spinal Cord ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Corticospinal Tract ◽  
Sympathetic Neurons ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Renal Sympathetic ◽  
Stimulation Of

Sympathetic preganglionic neurons and interneurons are closely apposed (presumably synapsed upon) by corticospinal tract (CST) axons. Sprouting of the thoracic CST rostral to lumbar spinal cord injuries (SCI) substantially increases the incidence of these appositions. To test our hypothesis that these additional synapses would increase CST control of sympathetic activity after SCI, we measured the effects of electrical stimulation of the CST on renal sympathetic nerve activity (RSNA) and arterial pressure (AP) in α-chloralose-anesthetized rats with either chronically intact or chronically lesioned spinal cords. Stimuli were delivered to the CST at intensities between 25–150 μA and frequencies between 25 and 75 Hz. Stimulation of the CST at the midcervical level decreased RSNA and AP. These decreases were not mediated by direct projections of the CST to the thoracic spinal cord because we could still elicit them by midcervical stimulation after acute lesions of the CST at caudal cervical levels. In contrast, caudal thoracic CST stimulation increased RSNA and AP. Neither the responses to cervical nor thoracic stimulation were affected by chronic lumbar SCI. These data show that the CST mediates decreases in RSNA via a cervical spinal system but excites spinal sympathetic neurons at caudal thoracic levels. Because chronic lumber spinal cord injury affected responses evoked from neither the cervical nor thoracic CST, we conclude that lesion-induced or regeneration-induced formation of new synapses between the CST and sympathetic neurons may not affect cardiovascular regulation.

A highly selective cardiorenal serotonergic 5-HT3-mediated reflex in rats

1993 ◽  
Vol 264 (6) ◽  
pp. H1871-H1877 ◽  
Author(s):  
R. Veelken ◽  
K. F. Hilgers ◽  
M. Leonard ◽  
K. Scrogin ◽  
J. Ruhe ◽  
...  
Keyword(s):  
Sympathetic Nerve ◽  
Receptor Agonist ◽  
Sympathetic Nerve Activity ◽  
Short Term ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Prolonged Stimulation ◽  
Saline Loading ◽  
Renal Sympathetic ◽  
Stimulation Of

To elucidate whether prolonged stimulation of cardiopulmonary serotonergic (5-HT3) receptors could play a role in the control of renal sympathetic nerve activity (RSNA), we compared 15-min intravenous infusions to bolus administrations of the 5-HT3 receptor agonist phenyl biguanide (PBG) and to a 0.9% saline load (5% body wt) in rats. Short-term and prolonged stimulation of 5-HT3-sensitive cardiopulmonary reflexes caused dose-related decreases in RSNA but not in lumbar sympathetic nerve activity (LSNA); only short-term stimulation caused decreases in blood pressure (BP) and heart rate (HR). Saline loading lowered RSNA but not LSNA, BP, or HR. Baroreceptor denervation did not influence any of these responses. Scopolamine attenuated BP and HR but not RSNA responses to bolus PBG. Pretreatment with a 5-HT3 receptor antagonist inhibited responses to PBG but not to saline. Vagotomy abolished all responses to all interventions. Thus 1) the prolonged stimulation of cardiopulmonary 5-HT3 receptors caused sustained suppression of RSNA, 2) decreased BP and HR were manifest only during short-term stimulation (3 min), and 3) blockade of 5-HT3 receptors did not influence responses to cardiopulmonary mechanoreceptor stimulation.

Effects of volume expansion on renal sympathetic nerve activity and cardiovascular and renal function in lambs

1992 ◽  
Vol 262 (4) ◽  
pp. R651-R658 ◽  
Author(s):  
F. G. Smith ◽  
J. M. Klinkefus ◽  
J. E. Robillard
Keyword(s):  
Renal Function ◽  
Sympathetic Nerve ◽  
Volume Expansion ◽  
Sympathetic Nerve Activity ◽  
Right Atrial ◽  
Nerve Activity ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Cardiopulmonary Baroreflex ◽  
Renal Sympathetic

To assess the cardiopulmonary baroreflex in the immature animal, effects of volume expansion on changes in right atrial pressure, renal sympathetic nerve activity, and renal function were measured in chronically instrumented newborn (4-8 days; n = 13) and older lambs (4-5 wk; n = 14). Studies were carried out for 30 min before and 2 h after volume expansion with 6% Dextran 70 (25 ml/kg). Right atrial pressure increased by 4.0 +/- 0.5 mmHg in newborns and by 8.8 +/- 0.6 mmHg in older lambs within 15 min of volume expansion (P less than 0.001). After volume expansion, heart rate decreased in newborns from 237 +/- 6 beats/min to a nadir of 211 +/- 7 beats/min 2 h later (P less than 0.001) but remained constant at control levels of 148 +/- 9 beats/min in older lambs. Maximal inhibition of renal sympathetic nerve activity was achieved at 15 min in older lambs (-50.1 +/- 7.5%) and at 60 min (-58.3 +/- 10.9%) in newborns in which there was a prolonged sympathoinhibition (P less than 0.001). There was also a significant diuretic response in both groups but a limited natriuretic response to volume expansion in newborns (P greater than 0.05) compared with older lambs (P less than 0.001). These data demonstrate the presence of the cardiopulmonary baroreflex in the first week of life in lambs. The sustained sympathoinhibition and bradycardia seen in response to volume expansion in newborns but not in older lambs support the hypothesis that the reflexes controlling arterial pressure and blood volume change with postnatal maturation.

Sign in / Sign up

Export Citation Format

Share Document