Alpha-adrenergic-mediated reflex responses to induced muscular contraction are changed with age in dogs

1993 ◽  
Vol 265 (6) ◽  
pp. H1899-H1908 ◽  
Author(s):  
G. C. Haidet
Keyword(s):  
Blood Flow ◽  
Regional Blood Flow ◽  
Muscular Contraction ◽  
Related Difference ◽  
Abdominal Organs ◽  
Age Related ◽  
Before And After ◽  
Alpha Blockade ◽  
Anesthetized Dogs ◽  
Age Related Changes

Aging significantly affects reflex cardiovascular (CV) responses to induced muscular contraction in anesthetized dogs. To further investigate whether age-related changes in alpha-adrenergic-mediated responses to muscular contraction contribute to these previously reported age-related changes in CV responses associated with advanced age, hemodynamic and regional blood flow (BF) responses at baseline and during hindlimb contraction (HLC) were evaluated both before and after alpha-blockade (alpha-AB) in older (8-14 yr old) and in younger (2-3 yr old) beagles during alpha-chloralose anesthesia. alpha-AB with phentolamine resulted in significant (P < 0.05) reductions in mean arterial pressure before and during HLC, regardless of age. However, age-related differences in the systemic vascular resistance, cardiac output, and stroke volume responses to HLC, observed before alpha-AB, were eliminated after phentolamine as the result of an age-related difference in each of these responses to alpha-AB. Baseline BF (microspheres) was unchanged after alpha-AB in seven of eight abdominal organs, regardless of age. However, reductions in BF during HLC were attenuated in seven of eight abdominal organs in the younger dogs after alpha-AB, but in none of these organs in the older dogs, indicative of diminished alpha-mediated vasoconstriction in these organs in the older dogs during HLC. Furthermore, the age-related difference in the combined BF reduction to all eight abdominal organs before alpha-AB was eliminated after alpha-AB. Finally, BF increases to two of four contracting muscles, as well as the combined increase in blood flow to all four contracting muscles, were attenuated after alpha-AB, regardless of age. These results demonstrate that alpha-blockade eliminates many of the age-related differences in CV responses to HLC observed before alpha-AB and suggest that alpha-adrenergic-mediated responses to HLC change with age in beagles.

Effect of age on cardiovascular responses to static muscular contraction in beagles

1992 ◽  
Vol 73 (6) ◽  
pp. 2320-2327 ◽  
Author(s):  
G. C. Haidet
Keyword(s):  
Skeletal Muscle ◽  
Heart Rate ◽  
Vascular Resistance ◽  
Regional Blood Flow ◽  
Cardiovascular Responses ◽  
Muscular Contraction ◽  
Abdominal Organs ◽  
Age Related ◽  
Muscle Groups ◽  
Alpha Chloralose

Induced muscular contraction in anesthetized animals results in significant hemodynamic and regional blood flow (RBF) changes. Although reflex cardiovascular responses initiated in contracting muscle have been firmly established, little is known about the effects of age on these responses. Because other reflex responses that involve sympathetic activation appear to be attenuated with age, it was hypothesized that reflex efferent cardiovascular responses that normally occur during muscular contraction would be impaired in senescent dogs. Therefore, hemodynamic and RBF responses to induced static hindlimb contraction (HLC) were evaluated in 8- to 14- and 2- to 3-yr-old beagles during alpha-chloralose anesthesia. Most baseline hemodynamic parameters were similar in both groups, but heart rate was significantly (P < 0.05) higher in old dogs. During HLC, heart rate and blood pressure increased in the young and old dogs. However, increases in stroke volume and cardiac output were greater in old dogs, combined with a reduction in systemic vascular resistance not observed in young dogs. No age-related difference in baseline RBF (microspheres) was observed in six of eight abdominal regional circulations and in each of four skeletal muscle groups. During HLC, RBF reductions occurred in six of eight abdominal organs in young and old dogs. However, the reduction in RBF and concomitant increase in vascular resistance in all eight abdominal regions combined was almost twice as great in young vs. old dogs. In noncontracting skeletal muscle, RBF decreased and vascular resistance increased four times more in young vs. old dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide as a regulator of adrenal blood flow

1993 ◽  
Vol 264 (2) ◽  
pp. H464-H469 ◽  
Author(s):  
M. J. Breslow ◽  
J. R. Tobin ◽  
D. S. Bredt ◽  
C. D. Ferris ◽  
S. H. Snyder ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Neural Control ◽  
Splanchnic Nerve ◽  
No Synthase ◽  
Catecholamine Secretion ◽  
Before And After ◽  
Anesthetized Dogs ◽  
Synthase Inhibitor ◽  
Splanchnic Nerve Stimulation

To determine whether nitric oxide (NO) is involved in adrenal medullary vasodilation during splanchnic nerve stimulation (NS)-induced catecholamine secretion, blood flow (Q) and secretory responses were measured in pentobarbital-anesthetized dogs before and after administration of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME). L-NAME (40 mg/kg iv over 5 min, followed by 40 mg.kg-1.h-1) reduced NO synthase activity of medullary and cortical homogenates from 5.2 +/- 0.3 to 0.7 +/- 0.1 pmol.min-1.mg protein-1 and from 1.2 +/- 0.2 pmol.min-1.mg protein-1 to undetectable levels, respectively. L-NAME reduced resting medullary and cortical Q by 42 and 60%, respectively. NS before L-NAME increased medullary Q from 181 +/- 16 to 937 +/- 159 ml.min-1.100 g-1 and epinephrine secretion from 1.9 +/- 0.8 to 781 +/- 331 ng/min. NS after L-NAME had no effect on medullary Q (103 +/- 14 vs. 188 +/- 34 ml.min-1.100 g-1), while epinephrine secretion increased to the same extent as in control animals (1.9 +/- 0.7 vs. 576 +/- 250 ng/min). L-NAME also unmasked NS-induced cortical vasoconstriction; cortical Q decreased from 96 +/- 8 to 50 +/- 5 ml.min-1.100 g-1. Administration of hexamethonium (30 mg/kg iv), a nicotinic receptor antagonist, reduced NS-induced epinephrine secretion by 90%. These data suggest independent neural control of medullary Q and catecholamine secretion, the former by NO and the latter by acetylcholine.

scholarly journals Steep head-down tilt has persisting effects on the distribution of pulmonary blood flow

2006 ◽  
Vol 101 (2) ◽  
pp. 583-589 ◽  
Author(s):  
A. Cortney Henderson ◽  
David L. Levin ◽  
Susan R. Hopkins ◽  
I. Mark Olfert ◽  
Richard B. Buxton ◽  
...  
Keyword(s):  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Regional Blood Flow ◽  
Flow Distribution ◽  
Normal Subjects ◽  
Relative Dispersion ◽  
Lung Water ◽  
Before And After ◽  
Capillary Pressures ◽  
The Right

Head-down tilt has been shown to increase lung water content in animals and alter the distribution of ventilation in humans; however, its effects on the distribution of pulmonary blood flow in humans are unknown. We hypothesized that head-down tilt would increase the heterogeneity of pulmonary blood flow in humans, an effect analogous to the changes seen in the distribution of ventilation, by increasing capillary hydrostatic pressure and fluid efflux in the lung. To test this, we evaluated changes in the distribution of pulmonary blood flow in seven normal subjects before and after 1 h of 30° head-down tilt using the magnetic resonance imaging technique of arterial spin labeling. Data were acquired in triplicate before tilt and at 10-min intervals for 1 h after tilt. Pulmonary blood flow heterogeneity was quantified by the relative dispersion (standard deviation/mean) of signal intensity for all voxels within the right lung. Relative dispersion was significantly increased by 29% after tilt and remained elevated during the 1 h of measurements after tilt (0.84 ± 0.06 pretilt, 1.09 ± 0.09 calculated for all time points posttilt, P < 0.05). We speculate that the mechanism most likely responsible for our findings is that increased pulmonary capillary pressures and fluid efflux in the lung resulting from head-down tilt alters regional blood flow distribution.

Regional blood flow and cardiac output during acute hypoxia in the anesthetized dog

1963 ◽  
Vol 204 (6) ◽  
pp. 963-968 ◽  
Author(s):  
John F. Murray ◽  
I. Maureen Young
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Regional Blood Flow ◽  
Acute Hypoxia ◽  
Arterial Oxygen Saturation ◽  
Head Kidney ◽  
Arterial Oxygen ◽  
Circulatory Effects ◽  
Low Concentrations ◽  
Anesthetized Dogs

The circulatory effects of breathing low concentrations of oxygen were studied in ten anesthetized dogs. Simultaneous measurements were made of cardiac output (indicator dilution technique) and blood flow to the head, kidney, and hind limb (electromagnetic flowmeters). Four experiments were performed with the addition of succinylcholine to inhibit the ventilatory response to hypoxia and maintain pCO2 constant. A rise in cardiac output and mean arterial pressure occurred which was significantly correlated to the decrease in arterial oxygen saturation. No threshold for these responses was found. Blood flow tended to increase during hypoxia in the regions studied but the responses were variable and only the change in renal blood flow had a significant correlation to arterial oxygen unsaturation. Systemic and regional vascular resistances during hypoxia varied both in direction and magnitude of change. The preponderant effects of hypoxia influence cardiac output more than peripheral vascular resistance.

474 AGE-RELATED CHANGES IN CEREBRAL BLOOD FLOW MAY EXPLAIN WORSE OUTCOME IN FEMALE HEAD TRAUMA PATIENTS

2005 ◽  
Vol 53 (1) ◽  
pp. S161.3-S161
Author(s):  
D. M. Lee ◽  
T. C. Glenn ◽  
W. J. Boscardin ◽  
J. F. Soustiel ◽  
N. A. Martin
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Head Trauma ◽  
Trauma Patients ◽  
Female Head ◽  
Age Related ◽  
Age Related Changes

Plasma dopamine in regulation of canine renal blood flow

1988 ◽  
Vol 255 (3) ◽  
pp. R379-R387 ◽  
Author(s):  
D. R. Kapusta ◽  
N. W. Robie
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Sch 23390 ◽  
Renal Perfusion ◽  
Receptor Activation ◽  
Renal Autoregulation ◽  
Alpha Adrenoceptor ◽  
Before And After ◽  
Anesthetized Dogs ◽  
Control Infusion

Studies were performed in pentobarbital-anesthetized dogs to determine whether circulating plasma dopamine (DA) is involved in renal blood flow (RBF) regulation. During graded reductions in renal perfusion pressure (RPP), total renal venous (RV) DA content significantly increased at RPPs below the autoregulatory range. The RBF response to decrements in RPP was also examined during control, infusion of DA (1.2 micrograms.kg(-1).min(-1)ia), and after DA receptor blockade by SCH 23390 (30 micrograms/kg iv). During DA infusion, autoregulation was still evident over the same RPPs, although at higher flow rates. At pressures below the autoregulatory range, RBF decreased linearly and the autoregulatory curve merged with control at 50 mmHg. After SCH 23390, autoregulation ceased at a higher RPP than during control, and RBF was significantly less than control rates at pressures of 80 mmHg and below. To elucidate reasons for this latter response, reductions in RPP were repeated before and after administration of both prazosin (0.1 mg/kg iv) and SCH 23390. The results indicated that RBF rates were not different from control at any RPP. Further, prazosin alone did not alter renal autoregulation but significantly increased RBF at RPP below the autoregulatory range. Thus these results indicate that dopamine does not participate in RBF control at pressures above the inflection point for the lowest limit of RBF autoregulation but may be released at lower RPP to act as a vasodilator agent to oppose alpha-adrenoceptor-mediated reductions in RBF. Moreover, tonic DA receptor activation may influence the setting of the lower limit of canine RBF autoregulation.

Hemodynimic effects of systemic and central administration of clonidine in the monkey

1975 ◽  
Vol 228 (4) ◽  
pp. 1276-1279 ◽  
Author(s):  
P Bolme ◽  
RP Forsyth ◽  
T Ishizaki ◽  
KL Melmon
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Regional Blood Flow ◽  
Systemic Arterial Pressure ◽  
Intraventricular Injection ◽  
Central Administration ◽  
New Information ◽  
Before And After ◽  
Microsphere Method ◽  
Radioactive Microsphere Method

Systemic and regional hemodynamic changes were measured in restrained, conscious rhesus monkeys with indwelling arterial and venous catheters before and after clonidine (5 and 15 mug/kg) was slowly infused intravenously or smaller doses (2 mug/kg) were injected into a lateral cerebral ventricle. Dye-dilution cardiac outputs and the complete distribution of cardiac output were obtained intermittently with the use of the radioactive microsphere method. After the higher intravenous dose and the intraventricular injection, systemic arterial pressure was significantly lowered for 30-45 min. Both of these groups had similar changes in the redistribution of cardiac output and blood flow that outlasted the hypotensive period. Blood flow was maintained or increased in the hepatic and renal arteries at the expense of skin; flow to skeletal muscle and brain also decreased during the first hour. These data support previous studies that indicate that the primary action of clonidine is in the central nervous system and, in addition, add new information about the regional blood flow changes evoked by clonidine.

scholarly journals Age-related changes in retrobulbar circulation: a literature review

2019 ◽  
Vol 40 (2) ◽  
pp. 493-501 ◽  
Author(s):  
Marta P. Wiącek ◽  
Monika Modrzejewska ◽  
Daniel Zaborski
Keyword(s):  
Blood Flow ◽  
Doppler Imaging ◽  
Colour Doppler ◽  
Colour Doppler Imaging ◽  
Age Related ◽  
Pubmed Database ◽  
Retrobulbar Blood Flow ◽  
Circulation Parameters ◽  
And Function ◽  
Age Related Changes

Abstract Introduction The advances in research methods used in ophthalmology allow for an increasingly accurate examination of the eyes, as well as the morphology and function of the vessels. Colour Doppler imaging is still the first-line method for the analysis of parameters of retrobulbar circulation. Therefore, the aim of this work was to present the current state of knowledge about anatomical and functional age-related changes in retrobulbar arteries. Methods A literature search was performed mainly based on the PubMed database. Results The anatomy of retrobulbar arteries, histological background of age-related vascular changes, age-related changes in retrobulbar blood flow in the ophthalmic artery, central retinal artery, short posterior ciliary arteries, and the reference values for the age-dependent retrobulbar circulation parameters measured by colour Doppler imaging are discussed in this review. Conclusion The age of the subject should always be taken into account when interpreting the parameters of retrobulbar blood flow measured by colour Doppler imaging.

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