Regulation of arterial blood pressure in Australian tiger snakes

1978 ◽  
Vol 75 (1) ◽  
pp. 65-79 ◽  
Author(s):  
H. B. Lillywhite ◽  
R. S. Seymour
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Complete Recovery ◽  
Pressure Control ◽  
Pressure Regulation ◽  
Body Temperatures ◽  
Heating And Cooling ◽  
Arterial Blood ◽  
Preferred Temperatures ◽  
Head Up Tilt

1. Blood pressure was measured in the dorsal aorta of restrained, unanaesthetized tiger snakes (Notechis scutatus) at different body temperatures during graded, passive tilt. Aortic blood pressure in horizontal snakes showed no significant change over a range of body temperatures between 18 and 33 degrees C (mean of measurements on 16 snakes = 42.2 +/− I.98 mmHg), while heart rate increased logarithmically (Q10 approximately 2.5). Blood pressure was stable during heating and cooling between body temperatures of 15 and 30 degrees C, but the pressure was 10--50% higher during heating than during cooling. 2. Head-up tilt usually caused a brief fall in pressure at heart level followed by partial or complete recovery and tachycardia. At the cessation of tilt, there was a characteristic overshoot of the blood pressure followed by readjustment to control (pretilt) levels. Head-down tilt typically increased pressure which then either stabilized or returned toward pretilt levels. Heart rate changes during head-down tilt were not consistent in direction or magnitude. Stabilized pressures at mid-body usually increased following head-up tilt and decreased following head-down tilt, indicating physiological adjustment to posture change. Blood pressure control was evident at body temperatures ranging from 10 to 38 degrees C, but was most effective at the higher and behaviourally preferred temperatures. 3. Propranolol lowered heart rate but did not influence pressure in horizontal snakes. During head-up tilt propranolol eliminated or reduced tachycardia and sometimes reduced the efficacy of pressure compensation for tilt. Phentolamine increased heart rate, lowered blood pressure, and eliminated pressure regulation during tilt. The results suggest that sympathetically mediated reflexes assist central blood pressure regulation in the tiger snake, with vasomotor adjustments having greater importance than changes in heart rate.

Compression Stocking Length Effects on Arterial Blood Pressure and Heart Rate Following Head-Up Tilt in Healthy Volunteers

2014 ◽  
Vol 63 (6) ◽  
pp. 435-438 ◽  
Author(s):  
Kunihiko Tanaka ◽  
Shiori Tokumiya ◽  
Yumiko Ishihara ◽  
Yumiko Kohira ◽  
Tetsuro Katafuchi
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Healthy Volunteers ◽  
Arterial Blood Pressure ◽  
Compression Stocking ◽  
Arterial Blood ◽  
Head Up Tilt ◽  
Length Effects

Reduced parasympathetic control of heart rate in obese dogs

1995 ◽  
Vol 269 (2) ◽  
pp. H629-H637 ◽  
Author(s):  
B. N. Van Vliet ◽  
J. E. Hall ◽  
H. L. Mizelle ◽  
J. P. Montani ◽  
M. J. Smith
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Rate Control ◽  
Saturated Fat ◽  
Pressure Control ◽  
Resting Heart Rate ◽  
Arterial Blood ◽  
Parasympathetic Control ◽  
The Mean ◽  
Affect Heart Rate

We investigated why resting heart rate is elevated in dogs fed a high saturated fat diet for 12.7 +/- 1.8 wk. Obese dogs exhibited elevated body weight (59%), blood pressure (14%), and heart rate (25%). Differences in resting heart rate (control, 58 +/- 5 beats/min; obese, 83 +/- 7 beats/min) were abolished after hexamethonium, indicating an autonomic mechanism. Hexamethonium also reduced blood pressure in obese (20 +/- 4 mmHg) but not control (9 +/- 6 mmHg) animals. Propranolol did not affect heart rate in either group, excluding a beta-adrenergic mechanism. Subsequent administration of atropine increased heart rate more in control than in obese dogs (110 +/- 9 vs. 57 +/- 11 beats/min). The sensitivity of the cardiac limb of the baroreflex (Oxford method) was reduced by 46% in the obese group, confirming impairment of the parasympathetic control of heart rate. The standard deviation of blood pressure measurements was normal when expressed as a percentage of the mean arterial blood pressure (control, 11.2 +/- 0.4%; obese, 11.2 +/- 0.5%). Our results indicate that the development of obesity in dogs fed a high saturated fat diet is accompanied by an attenuated resting and reflex parasympathetic control of heart rate.

Endogenous Opioids Modulate Central Nervous System Blood Pressure Control in Man

1982 ◽  
Vol 63 (s8) ◽  
pp. 331s-333s ◽  
Author(s):  
P. C. Rubin ◽  
Kathleen McLean ◽  
J. L. Reid
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Pressure Control ◽  
Normal Subjects ◽  
Pressure Control ◽  
Endogenous Opioids ◽  
Plasma Noradrenaline ◽  
Head Up Tilt ◽  
Blind Manner

1. Two studies were performed to elucidate the role of opioids in blood pressure control in man. 2. Study 1: nine normal subjects, 18–32 years, received in a randomized single blind manner, volume matched infusions of a Met-enkephalin analogue (DAMME) 0.5 mg, naloxone 0.2 mg/kg or saline. Blood pressure, heart rate and plasma noradrenaline were determined supine and after a 5 min, 70° head-up tilt at 0, 3/4, 2, 3, 4, 5 and 6 h. 3. Study 2: seven subjects, after baseline recordings of blood pressure and heart rate received six incremental infusions of sodium nitroprusside, 1.5–7.5 μg min−1 kg−1. They then received DAMME or naloxone and the nitroprusside infusions were repeated between 3 and 4 h. There was a significant linear relationship between fall in mean arterial pressure and rise in heart rate in each case and the slope was used as an index of baroreflex sensitivity. 4. Neither naloxone nor DAMME influenced supine blood pressure or heart rate. Blood pressure after head-up tilt was significantly (analysis of variance) decreased by DAMME for up to 5 h but not by naloxone, the effect being most marked at 3 h: systolic (mean ± sd), placebo 110 ± 6, naloxone 106 ± 10, DAMME 96 ± 16 (P< 0.02); diastolic (mean ± sd), placebo 78 ± 7, naloxone 79 ± 5, DAMME 67 ± 8 (P < 0.01). The increases in heart rate and plasma noradrenaline on tilting after DAMME were not significantly different from values with placebo or naloxone. The 3 h values for heart rate were: placebo 87 ± 16, naloxone 88 ± 19, DAMME 89 ± 23 (P > 0.1); for plasma noradrenaline (nmol/l): placebo 6.0 ± 2.2, naloxone 5.8 ± 1.9, DAMME 6.0 ± 1.9 (P > 0.1). 5. Naloxone significantly increased the slope (beats per min/mmHg) of the regression relationship from a mean of 1.8 ± 0.07 to 3.0 ± 1.3 (P < 0.05), and DAMME reduced the slope from 2.7 ± 1.7 to 1.2 ± 0.5 (P < 0.05). 6. We conclude that endogenous opioids modulate baroreflex function in man.

Is baroreflex control of sympathetic activity and heart rate active in the preterm fetal sheep?

2009 ◽  
Vol 296 (3) ◽  
pp. R603-R609 ◽  
Author(s):  
Lindsea C. Booth ◽  
Simon C. Malpas ◽  
Carolyn J. Barrett ◽  
Sarah-Jane Guild ◽  
Alistair J. Gunn ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Pressure Control ◽  
Autonomic Response ◽  
Nerve Activity ◽  
Baroreflex Control ◽  
Fetal Sheep ◽  
Arterial Blood

The arterial baroreflex is a fundamental reflex that buffers rapid changes in arterial blood pressure (BP) via regulation of the heart rate and sympathetic nerve activity to the vasculature. In adults a sigmoidal relationship between BP and both heart rate and sympathetic nerve activity is well documented. Its role in blood pressure control before birth is unclear. Preterm babies have a high incidence of low BP, especially in the first few days of life, which could be related, in part, to immaturity of the baroreflex. In the present study, we investigated the baroreflex control of fetal heart rate and renal sympathetic nerve activity (RSNA) in preterm fetal sheep in utero (102 ± 1 days of gestation; term 140 days). Phenylephrine was associated with a significant increase in BP from 38 ± 2 to 58 ± 3 mmHg and a decrease in heart rate (HR) from 177 ± 4 to 116 ± 8 beats per minute (bpm). Sodium nitroprusside was associated with a significant fall in BP from 38 ± 2 to 26 ± 1 mmHg and an increase in HR from 182 ± 4 to 274 ± 8 bpm. However, the time between the 50% changes in BP and HR was significantly greater after hypotension than hypertension (31 ± 8 s vs. 14 ± 5 s, P < 0.05). No significant changes in RSNA occurred with either stimulus. This suggests that there are different maturational tempos for the components of the central autonomic response to altered blood pressure.

scholarly journals Distinct neurohumoral biomarker profiles in children with hemodynamically defined orthostatic intolerance may predict treatment options

2016 ◽  
Vol 310 (3) ◽  
pp. H416-H425 ◽  
Author(s):  
Ashley L. Wagoner ◽  
Hossam A. Shaltout ◽  
John E. Fortunato ◽  
Debra I. Diz
Keyword(s):  
Blood Pressure ◽  
Orthostatic Intolerance ◽  
Treatment Options ◽  
Pressure Control ◽  
Hemodynamic Response ◽  
Postural Orthostatic Tachycardia Syndrome ◽  
Compensatory Mechanisms ◽  
Oh Groups ◽  
Arterial Blood ◽  
Head Up Tilt

Studies of adults with orthostatic intolerance (OI) have revealed altered neurohumoral responses to orthostasis, which provide mechanistic insights into the dysregulation of blood pressure control. Similar studies in children with OI providing a thorough neurohumoral profile are lacking. The objective of the present study was to determine the cardiovascular and neurohumoral profile in adolescent subjects presenting with OI. Subjects at 10–18 yr of age were prospectively recruited if they exhibited two or more traditional OI symptoms and were referred for head-up tilt (HUT) testing. Circulating catecholamines, vasopressin, aldosterone, renin, and angiotensins were measured in the supine position and after 15 min of 70° tilt. Heart rate and blood pressure were continuously measured. Of the 48 patients, 30 patients had an abnormal tilt. Subjects with an abnormal tilt had lower systolic, diastolic, and mean arterial blood pressures during tilt, significantly higher levels of vasopressin during HUT, and relatively higher catecholamines and ANG II during HUT than subjects with a normal tilt. Distinct neurohumoral profiles were observed when OI subjects were placed into the following groups defined by the hemodynamic response: postural orthostatic tachycardia syndrome (POTS), orthostatic hypotension (OH), syncope, and POTS/syncope. Key characteristics included higher HUT-induced norepinephrine in POTS subjects, higher vasopressin in OH and syncope subjects, and higher supine and HUT aldosterone in OH subjects. In conclusion, children with OI and an abnormal response to tilt exhibit distinct neurohumoral profiles associated with the type of the hemodynamic response during orthostatic challenge. Elevated arginine vasopressin levels in syncope and OH groups are likely an exaggerated response to decreased blood flow not compensated by higher norepinephrine levels, as observed in POTS subjects. These different compensatory mechanisms support the role of measuring neurohumoral profiles toward the goal of selecting more focused and mechanistic-based treatment options for pediatric patients with OI.

Heterogeneity of responses to orthostatic stress in homozygous twins

2007 ◽  
Vol 102 (1) ◽  
pp. 249-254 ◽  
Author(s):  
D. D. O'Leary ◽  
R. L. Hughson ◽  
J. K. Shoemaker ◽  
D. K. Greaves ◽  
D. E. Watenpaugh ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Environmental Factors ◽  
Cardiovascular Regulation ◽  
Identical Twins ◽  
Orthostatic Stress ◽  
Orthostatic Tolerance ◽  
Arterial Blood ◽  
Head Up Tilt

Early analysis into the role of genetics on cardiovascular regulation has been accomplished by comparing blood pressure and heart rate in homozygous twins during unstressed, resting physiological conditions. However, many variables, including cognitive and environmental factors, contribute to the regulation of cardiovascular hemodynamics. Therefore, the purpose of this study was to determine the hemodynamic response of identical twins to an orthostatic stress, ranging from supine rest to presyncope. Heart rate, arterial blood pressure, middle cerebral artery blood velocity, an index of cerebrovascular resistance, cardiac output, total peripheral resistance, and end-tidal carbon dioxide were measured in 16 healthy monozygotic twin pairs. Five minutes of supine resting baseline data were collected, followed by 5 min of 60° head-up tilt. After 5 min of head-up tilt, lower body negative pressure was applied in increments of 10 mmHg every 3 min until the onset of presyncope, at which time the subject was returned to the supine position for a 5-min recovery period. The data indicate that cardiovascular regulation under orthostatic stress demonstrates a significant degree of variance between identical twins, despite similar orthostatic tolerance. As the level of stress increases, so does the difference in the cardiovascular response within a twin pair. The elevated variance with increasing stress may be due to an increase in the role of environmental factors, as the influential role of genetics nears a functional limit. Therefore, although orthostatic tolerance times were very similar between identical twins, the mechanism involved in sustaining cardiovascular function during increasing stress was different.

Regulation of arterial blood pressure in the common green iguana

1975 ◽  
Vol 228 (2) ◽  
pp. 386-391 ◽  
Author(s):  
LA Hohnke
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Arterial Pressure ◽  
Arterial Blood Pressure ◽  
Venous Pressure ◽  
Arterial Blood Flow ◽  
Arterial Blood ◽  
Head Up Tilt ◽  
Carotid Arterial

Arterial blood pressure (ABP) responses to graded hemorrhage and passive head-up tilt were studied in restrained, anesthetized, and unanesthetized iguanas. The ABP fell slowly in response to hemorrhage up to a critical deficit of 35 plus or minus 19% of the estimated blood volume; the rate of ABP fall then increased nearly 40-fold to continued hemorrhage. Increased heart rate and decreased femoral arterial blood flow accompanied progressive hemorrhage. Propranolol (2-3 mug/kg) did not appreciably alter arterial pressure-hemorrhage curves but hemorrhage-induced increases in heart rate were diminished nearly 50%. Atropine had little effect on either the blood pressure or heart rate changes induced by hemorrhage. During passive tilts of 0-90 degrees carotid arterial pressure fell 33% before returning to control levels (2 min). Heart rate increased and femoral arterial blood flow and central venous pressure fell in response to head-up tilts. It is concluded that hemorrhage and passive head-up tilting can induce reflex cardiovascular changes that assist ABP regulation in iguanas.

Effects of Enkephalins on Arterial Blood Pressure are Reduced by Propranolol

1978 ◽  
Vol 55 (s4) ◽  
pp. 237s-241s ◽  
Author(s):  
W. Simon ◽  
K. Schaz ◽  
U. Ganten ◽  
G. Stock ◽  
K. H. Schlör ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Cardiovascular Effects ◽  
Pressure Control ◽  
Methionine Enkephalin ◽  
Leucine Enkephalin ◽  
Arterial Blood ◽  
Wistar Kyoto ◽  
Blood Pressure Responses ◽  
The Brain

1. The cardiovascular effects of enkephalins have been tested in normotensive Wistar—Kyoto rats. Methionine—enkephalin and leucine—enkephalin increased blood pressure and heart rate after infusion into the brain ventricles. 2. After intravenous injection, blood pressure was increased by methionine—enkephalin and leucine—enkephalin, but heart rate was increased by methionine—enkephalin only. 3. Propranolol treatment reduced the increases in blood pressure following intraventricular methionine—enkephalin and leucine—enkephalin, while only the methionine—enkephalin-induced increases in heart rate were reduced by propranolol. 4. Heart rate and blood pressure responses after intravenous administration of methionine— enkephalins and leucine—enkephalin were not affected by propranolol. 5. Since opioid peptides occur in the blood and in regions of the brain involved in blood pressure regulation, the demonstrated cardiovascular effects to intraventricular and intravenous enkephalins support a role of these peptides in central and peripheral mechanisms of blood pressure control.

Arterial blood pressure control during hindlimb and forelimb contraction in the dog

1985 ◽  
Vol 248 (5) ◽  
pp. H678-H687
Author(s):  
O. Beaty
Keyword(s):  
Blood Pressure ◽  
Skeletal Muscle ◽  
Heart Rate ◽  
Muscle Contraction ◽  
Arterial Blood Pressure ◽  
Cardiovascular Responses ◽  
Pressure Control ◽  
Arterial Blood ◽  
Vascular Bed ◽  
Skeletal Muscle Contraction

This study examined the differential reflex cardiovascular responses evoked by separate contractions of the right hindlimb and forelimb and established the mechanism of a regional reflex vasodilation associated with hindlimb skeletal muscle contraction. The two groups of skeletal muscle were contracted separately by electrical stimulation (2-48 Hz) of the peripheral motor nerves. The left nonexercising hindlimb was perfused at constant flow. All blood pressure-regulating mechanisms were intact. Arterial blood pressure (ABP), left nonexercising hindlimb perfusion pressure (HLPP), and heart rate (HR) were recorded. HR was increased by skeletal muscle contraction. This response was independent of muscle group and contraction frequency. Increases in both ABP and HLPP were produced by high-frequency contractions (greater than 16 Hz) of either the hindlimb or forelimb. Decreases were evoked only by hindlimb contractions (greater than 8 Hz). The nonexercising skeletal muscle vascular bed contributed to this systemic depressor response by vasodilating. The mechanism involved a contraction-induced withdrawal of sympathetic nerve activity to that vascular bed. Concomitant with this response was an increase in heart rate that was blocked with propranolol. Similar heart rate changes evoked by forelimb contractions also were blocked with propranolol. These data indicate that sympathetic outflow to resting skeletal muscle depends on the origin and magnitude of the afferent signal from the contracting skeletal muscle.

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