Post-Adrenalectomy Hypotension in Rats; Absence of Baroreflex Resetting or Effect of Naloxone

1983 ◽  
Vol 64 (4) ◽  
pp. 371-376 ◽  
Author(s):  
S. M. Gardiner ◽  
T. Bennett
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Tap Water ◽  
Sinus Node ◽  
Pulse Interval ◽  
Baroreflex Control ◽  
Systemic Arterial Blood Pressure ◽  
Arterial Blood ◽  
Blood Pressures ◽  
Adrenalectomized Rats

1. Male Wistar rats were either bilaterally adrenalectomized or sham-operated, and given 1% sodium chloride solution instead of tap water to drink. Seven days later, arterial blood pressures were recorded directly from conscious freely moving rats. 2. Systolic and diastolic blood pressures were significantly lower in the adrenalectomized rats, whereas heart rates were significantly higher than in sham-operated animals. The tachycardia was due to a combination of sympathetic hyperactivity and reduced vagal tone, which may have been reflex responses to a reduction in effective blood volume. 3. Baroreflex control of the sinus node was assessed from the pulse interval responses to rises (induced by methoxamine) or falls (induced by glyceryl trinitrate or sodium nitroprusside) in systemic arterial blood pressure. The relation between pulse interval and systolic blood pressure was described by the same curve in sham-operated and adrenalectomized rats, indicating that, in the latter, there was no change in baroreflex setting or sensitivity. 4. Intravenous administration of naloxone (2mg/kg) had no effect on systemic arterial blood pressure in adrenalectomized rats, suggesting that endogenous opiates were not contributing to the hypotension.

scholarly journals Cardiac and vasomotor components of the carotid baroreflex control of arterial blood pressure during isometric exercise in humans

2006 ◽  
Vol 572 (3) ◽  
pp. 869-880 ◽  
Author(s):  
James P. Fisher ◽  
Shigehiko Ogoh ◽  
Ellen A. Dawson ◽  
Paul J. Fadel ◽  
Niels H. Secher ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Isometric Exercise ◽  
Baroreflex Control ◽  
Arterial Blood ◽  
Carotid Baroreflex ◽  
Exercise In Humans

Abstract 15839: Effect of Serotonin Neuron Depletion on Arterial Blood Pressure Regulation in Young Rats

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Jennifer Magnusson ◽  
Kevin Cummings
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Recovery Period ◽  
Sudden Infant Death ◽  
Sudden Infant ◽  
Sprague Dawley ◽  
Baroreflex Control ◽  
Hypoxic Conditions ◽  
Arterial Blood

Infants dying of Sudden Infant Death Syndrome (SIDS) have reduced brainstem serotonin (5-hydroxytryptamine, 5-HT) where some cases die following episodes of severe bradycardia and hypoxemia. The specific role of central 5-HT in resting arterial blood pressure (BP) and on baroreflex sensitivity during neonatal life has not been studied. In adult animals, systemic depletion of 5-HT increases BP with no effect on heart rate (HR) and reduces the sensitivity of the baroreflex. Other studies have also shown that a loss of central 5-HT beginning in embryogenesis reduces resting BP and HR in adulthood. Based on these reports, we hypothesized that loss of brainstem 5-HT neurons in the neonatal period would reduce baseline BP and HR as well as reduce baroreflex gain. To test this, we utilized 3-week old Sprague Dawley rats treated centrally with 5,7-dihydroxytryptamine (5,7-DHT, n=4; ~120 ug in saline, i.c.v.), a chemical that is toxic to serotonergic neurons. Littermate controls were injected with saline (CTRL, n=5, ~3ul, i.c.v.). We measured BP with a femoral artery catheter. HR was derived from BP. Following a recovery period, we measured resting variables for 15 minutes and then injected phenylephrine (PE; 3mg/kg s.c.) followed by sodium nitroprusside (SNP; 2.5mg/kg s.c.), separated by 15 minutes, to induce pressor or depressor responses, respectively. For both responses, baroreflex gain was calculated as the [[Unable to Display Character: &#8710;]]HR at the maximum [[Unable to Display Character: &#8710;]]BP following drug injection. We found that a loss of 5-HT neurons did not alter baseline BP (p>0.05) but did reduce baseline HR when compared to control littermates (p<0.02). 5-HT neuron deficiency tended to reduce baroreflex gain in response to PE (CTRL: -2.756 ± 0.483 beats/mmHg; 5,7-DHT: -1.499 ± 0.348 beats/mmHg; p=0.058), but not SNP (CTRL: -2.408 ± 0.351 beats/mmHg; 5,7-DHT: -3.316 ± 1.214 beats/mmHg; p>0.05). Our data indicate that brainstem 5-HT maintains resting HR, and is involved in baroreflex control of HR in response to hypertensive stimuli. Reduced brainstem 5-HT may predispose an infant to SIDS via altered autonomic control of BP and HR. The role of 5-HT in BP regulation during hypoxic conditions remains to be elucidated.

24-hour homeodynamic states of arterial blood pressure and pulse interval in conscious rats

1992 ◽  
Vol 73 (2) ◽  
pp. 754-761 ◽  
Author(s):  
B. J. Janssen ◽  
C. M. Tyssen ◽  
H. A. Struijker Boudier ◽  
P. M. Hutchins
Keyword(s):  
Blood Pressure ◽  
Cardiovascular System ◽  
Arterial Blood Pressure ◽  
Single Mode ◽  
Pulse Interval ◽  
Mean Values ◽  
Frequency Distributions ◽  
Set Point ◽  
Arterial Blood ◽  
Wistar Kyoto

In models that describe the homeostasis of the circulation, arterial blood pressure is usually expressed as a single value, which is regarded as the set point in such systems. The aim of the study was to identify in rats from 24-h beat-to-beat recordings the value of blood pressure that describes best such a set point of the cardiovascular system. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), kept on a 12:12-h lights on-off cycle, were instrumented for computerized 24-h beat-to-beat recording of mean arterial pressure (MAP) and pulse interval (PI). Three-dimensional frequency distributions were constructed by plotting for each beat its MAP vs. its PI. During the dark period, the concurrent distribution of MAP and PI showed two distinct modes while during the light period a single mode was found. Comparable patterns were found in SHRs and WKYs. These three different modes were significantly different from the mathematically calculated mean values of MAP and PI over these periods. Thus in rats the 24-h behavior of the cardiovascular system is better described by dynamic shifts between different modes (homeodynamic states) than by a single set point.

scholarly journals Vascular responsiveness in adrenalectomized rats with corticosterone replacement

1989 ◽  
Vol 256 (5) ◽  
pp. H1274-H1281 ◽  
Author(s):  
D. N. Darlington ◽  
K. Kaship ◽  
L. C. Keil ◽  
M. F. Dallman
Keyword(s):  
Blood Pressure ◽  
Body Weight ◽  
Arterial Blood Pressure ◽  
Body Weight Gain ◽  
Arterial Blood ◽  
Thymus Weight ◽  
Vascular Responsiveness ◽  
Vascular Sensitivity ◽  
Four Levels ◽  
Adrenalectomized Rats

To determine under resting, unstressed conditions the circulating glucocorticoid concentrations that best maintain sensitivity of the vascular smooth muscle and baroreceptor responses to vasoactive agents, rats with vascular cannulas were sham-adrenalectomized (sham) or adrenalectomized (ADRX) and provided with four levels of corticosterone replacement (approximately 100 mg fused pellets of corticosterone: cholesterol 0, 20, 40, and 80% implanted subcutaneously at the time of adrenal surgery). Changes in vascular and baroreflex responses were determined after intravenous injection of varying doses of phenylephrine and nitroglycerin with measurement of arterial blood pressure and heart rate in the conscious, chronically cannulated rats. Vascular sensitivity was decreased, and resting arterial blood pressure tended to be decreased in the adrenalectomized rats; both were restored to normal with levels of corticosterone (40%), which also maintained body weight gain, thymus weight, and plasma corticosteroid binding globulin concentrations at normal values. The baroreflex curve generated from the sham group was different from the curves generated from the ADRX+0, 20, and 40% groups, but not different from that of the ADRX+80% group, suggesting that the baroreflex is maintained by higher levels of corticosterone than are necessary for the maintenance of the other variables. These data demonstrate that physiological levels of corticosterone (40% pellet) restore vascular responsiveness, body weight, thymus weight, and transcortin levels to normal in ADRX rats, whereas higher levels (80% pellet) are necessary for restoration of the baroreflex.

Seizure-related modulation of systemic arterial blood pressure in focal epilepsy

Epilepsia ◽  
2016 ◽  
Vol 57 (10) ◽  
pp. 1709-1718 ◽  
Author(s):  
Kevin G. Hampel ◽  
Amirhossein Jahanbekam ◽  
Christian E. Elger ◽  
Rainer Surges
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Focal Epilepsy ◽  
Systemic Arterial Blood Pressure ◽  
Arterial Blood

Baroreflex control of muscle sympathetic nerve activity during skin surface cooling

2007 ◽  
Vol 103 (4) ◽  
pp. 1284-1289 ◽  
Author(s):  
Jian Cui ◽  
Sylvain Durand ◽  
Craig G. Crandall
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Arterial Blood Pressure ◽  
Sympathetic Nerve Activity ◽  
Muscle Sympathetic Nerve Activity ◽  
Skin Surface ◽  
Surface Cooling ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Arterial Blood

Skin surface cooling improves orthostatic tolerance through a yet to be identified mechanism. One possibility is that skin surface cooling increases the gain of baroreflex control of efferent responses contributing to the maintenance of blood pressure. To test this hypothesis, muscle sympathetic nerve activity (MSNA), arterial blood pressure, and heart rate were recorded in nine healthy subjects during both normothermic and skin surface cooling conditions, while baroreflex control of MSNA and heart rate were assessed during rapid pharmacologically induced changes in arterial blood pressure. Skin surface cooling decreased mean skin temperature (34.9 ± 0.2 to 29.8 ± 0.6°C; P < 0.001) and increased mean arterial blood pressure (85 ± 2 to 93 ± 3 mmHg; P < 0.001) without changing MSNA ( P = 0.47) or heart rate ( P = 0.21). The slope of the relationship between MSNA and diastolic blood pressure during skin surface cooling (−3.54 ± 0.29 units·beat−1·mmHg−1) was not significantly different from normothermic conditions (−2.94 ± 0.21 units·beat−1·mmHg−1; P = 0.19). The slope depicting baroreflex control of heart rate was also not altered by skin surface cooling. However, skin surface cooling shifted the “operating point” of both baroreflex curves to high arterial blood pressures (i.e., rightward shift). Resetting baroreflex curves to higher pressure might contribute to the elevations in orthostatic tolerance associated with skin surface cooling.

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