Dorsal Aortic Blood Pressure Research Articles

Coronary blood flow in vivo in the coho salmon (Oncorhynchus kisutch).

The effects of adrenergic agonists on dorsal aortic blood pressure, cardiac output, and coronary blood flow were studied in unrestrained coho salmon, Oncorhynchus kisutch. Resting coronary blood flow was 0.43 ml.min-1.kg body mass-1, which represented 1.1% of cardiac output or approximately 0.5 ml.min-1.g-1 compact ventricular mass calculated on 40% of total ventricle mass. Coronary blood flow was phasic and continuous throughout the cardiac cycle; flow seems to be affected by the ventricular contraction, with a peak flow occurring during diastole and a nadir in early systole. Epinephrine injections into the dorsal aorta resulted in a rapid increase in coronary blood flow in association with a rapid increase in dorsal aortic blood pressure. Subsequently there was also a slower increase in coronary vascular resistance, which could be blocked by phentolamine, indicating an alpha-adrenergic vasoconstriction. Isoprenaline injection produced an increase in coronary blood flow and a large reduction in coronary vascular resistance. The coronary vasodilatation was blocked by propranolol, indicating that it may be partly due to a beta-adrenergic vasodilatation. Preliminary results showed a marked increase in coronary blood flow associated with exposure to environmental hypoxia.

The Effect of Catecholamines, Substance P and Vasoactive Intestinal Polypeptide on Blood Flow to the Gut In the Dogfish Squalus Acanthias

ABSTRACT The effects of adrenaline, noradrenaline, substance P and vasoactive intestinal polypeptide (VIP) on dorsal aortic blood pressure, coeliac artery blood flow and heart rate were studied in unrestrained dogfish, Squalus acanthias. Changes in the coeliac vascular bed were calculated from these variables. Perfused tail preparations were used to study the effects of the various drugs on the somatic vascular bed. Corrosion casts were made to study the gross architecture of the coeliac vascular bed. Adrenaline and noradrenaline increased dorsal aortic pressure and reduced the coeliac artery blood flow. Adrenaline caused a small increase in heart rate while noradrenaline caused a small decrease. Both drugs increased the resistance in the coeliac vascular bed. VIP increased dorsal aortic pressure, heart rate and resistance in the coeliac vascular bed. Substance P caused an increase in heart rate, cardiac output and, in particular, in coeliac artery blood flow; dorsal aortic pressure was simultaneously reduced. Voluntary swimming or fright immediately caused a pronounced reduction in blood flow in the coeliac artery, even though cardiac output and dorsal aortic pressure increased. It is concluded that adrenergic mechanisms and possibly VIP are involved in reducing the blood flow to the gut, while substance P increases the flow to the gut.

Effects of Exercise, Hypoxia and Feeding on the Gastrointestinal Blood flow in the Atlantic Cod Gadus Morhua

Cardiac output, ventral and dorsal aortic blood pressure, heart rate, and coeliac and mesenteric artery blood flow were recorded simultaneously in the Atlantic cod, Gadus morhua L., at rest, during exercise, during hypoxia and after feeding. In the resting unfed animals, coeliac artery blood flow was 4.1 +/- 0.8 ml min-1 kg-1 and mesenteric artery blood flow was 3.5 +/- 1.1 ml min-1 kg-1 (mean +/- S.E.M., N = 10); together, these flows represent approximately 40% of the cardiac output. Exercise or exposure to hypoxia resulted in increased visceral vascular resistance, leading to reductions in the coeliac and mesenteric artery blood flows. Coeliac and mesenteric blood flows were increased 24 h after feeding and the coeliac and systemic vascular resistances decreased in comparison with the prefeeding values. Phentolamine did not affect the gastrointestinal artery blood flow, but produced a significant decrease in the mesenteric and systemic vascular resistance. Treatment with bretylium and phentolamine revealed differences between the coeliac and the mesenteric vasculature regarding the control mechanisms during hypoxia and during exercise and feeding. During hypoxia, an adrenergic control of the gastrointestinal vasculature with both nervous and humoral components was found, whereas during exercise and after feeding an additional non-adrenergic mechanism controlling gut blood flow was demonstrated.

Metabolic and cardiac scope of high energy demand teleosts, the tunas

The maximum aerobic metabolic rates of tunas are far above those of other fishes. In this review we attempt to define features of the cardiovascular system that may account for this extreme performance. Tuna hearts are much larger than those of most other fishes and are half the mass of those of similarly sized mammals; however, the ratio of compact to spongy myocardium is not (except for one tuna species) higher than in other active teleosts. Myocardial aerobic enzyme activity levels are not significantly elevated. The cardiac outputs of spinally blocked skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) are roughly 4 times those of other active teleosts. Ventral aortic blood pressures are the highest among all fishes (more than twice those of rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri)), and appear to be due to a high resistance to blood flow in the gills, since dorsal aortic blood pressures are not exceptional. Heart rates, cardiac output, and ventilation volume are high, but gill ventilation and perfusion appear to be well matched (i.e., gill ventilation: perfusion conductance ratios of ≈1). Blood hemoglobin concentrations of tunas are elevated, essentially identical with those of humans and twice those seen in other fishes. Because their blood oxygen carrying capacity is high and because skipjack and yellowfin tunas appear to be able to increase the minimum observed arterial to venous oxygen content differences approximately 3 times, we predict that they need to increase cardiac output only about 2 times during maximum rates of oxygen uptake. This ratio is not very different from those of other teleosts.

Hypotensive effect of atrial natriuretic factor (ANF) in the atlantic cod, Gadus morhua

1. The effect of two ANP/CDD-like peptides (rat ANF 8–33 and human cardiodilatin 1–16) on the cardiovascular system in vivo of the Atlantic cod was investigated. 2. Rat ANF (10 −12–10 −8mol.kg −1) produced tachycardia and a decrease in both ventral and dorsal aortic blood pressure. Human cardiodilatin (10 −12–10 −8mol.kg −1) had no visible effect on any of the recorded parameters. 3. Bilateral vagotomy or injection of atropine abolished the tachycardia, while the hypotensive effect remained. 4. It is concluded that while the effect of ANF on the vasculature may be direct, the cardiac effect is due to modulation of the cholinergic vagal inhibitory tonus to the heart.

Autonomic nervous control of blood pressure and heart rate during hypoxia in the cod, Gadus morhua

The autonomic nervous and possible adrenergic humoral control of blood pressure and heart rate during hypoxia was investigated in Atlantic cod. The oxygen tension in the water was reduced to 4.0–5.3 kPa (i.e.. PwO2=30–40 mmHg), and the fish responded with an immediate increase in ventral and dorsal aortic blood pressure (PvaPda), as well as a slowly developing bradycardia. The plasma concentrations of circulating catecholamines increased during hypoxia with a peak in the plasma level of noradrenaline occurring before the peak for adrenaline. Bretylium was used as a chemical tool to differentiate between neuronal and humoral adrenergic control of blood pressure and heart rate (fH) during hypoxia. The increase in Pva and Pda in response to hypoxia was strongly reduced in bretylium-treated cod, which suggests that adrenergic nerves are responsible for hypoxic hypertension. In addition, a small contribution by circulating catecholamines to the adrenergic tonus affecting Pva during hypoxia was suggested by the decrease in Pva induced by injection of the α-adrenoceptor antagonist phentolamine. The cholinergic and the adrenergic tonus affecting heart rate were estimated by injections of atropine and the β-adrenoceptor antagonist sotalol. The experiments demonstrate an increased cholicholinergic as well as adrenergic tonus on the heart during hypoxia.

Effects of Hypoxia and Drugs on the Cardiovascular Dynamics of the Atlantic HagfishMyxine Glutinosa

ABSTRACTCardiac output, ventral and dorsal aortic blood pressure and heart rate were recorded simultaneously in unanaesthetized hagfish, Myxine glutinosa L. Mean cardiac output was 8.7 ml min−1 kg−1 and mean heart rate 22.3 beats min−1. The absence of beat-to-beat oscillations in heart rate was consistent with the lack of an extrinsic cardiac innervation in hagfish. Mean blood pressures were 1.04 kPa (ventral aorta) and 0.77kPa (dorsal aorta).Injection of adrenaline into the caudal vein significantly increased cardiac output, stroke volume, heart rate and blood pressures of both aortas. Peak cardiac output was close to 25 ml min−1 kg−1. Injection of the β-adrenoreceptor antagonist sotalol decreased resting heart rate significantly. We conclude that endogenous catecholamines from chromaffin cells of the heart are instrumental in the regulation of cardiac function in Myxine.Injection of acetylcholine had little direct effect on the recorded cardiac variables, but caused marked branchial vasoconstriction. Heart rate increased as the pressor response subsided. The cholinergic antagonist atropine had no effect on any of the resting parameters.Injection of adenosine had no direct cardiac effects but reduced the systemic vascular resistance.Severe hypoxia (kPa for 15–35 min) had very little effect on the cardiovascular variables recorded. The remarkable ability of the hagfish heart to maintain normal cardiac output during severe hypoxia is discussed with respect to the anaerobic pumping capacity of the heart.Pump-perfused, in situ gill preparations were used to examine branchial vasoactivity. Acetylcholine and adrenaline produced dose-dependent vasoconstriction, whereas isoprenaline, noradrenaline and adenosine dilated the branchial vasculature.

Regulation of cardiac output and gut blood flow in the sea raven,Hemitripterus americanus

Coeliac artery blood flow (Fca) before and after feeding was recorded in the sea raven. To obtain basic information about the scope of cardiovascular adjustment in the sea raven, a separate series of experiments was performed, in which ventral (Pva), and dorsal (Pda) aortic blood pressure, heart rate (HR) and cardiac output (jaz) were monitored during rest and encouraged exercise.Measurements of coeliac artery flow showed that visceral blood flow is substantial, particularly after feeding, and variations in the visceral vascular conductance affect Pda directly. Simultaneous recordings of intestinal and dorsal aortic blood pressures showed no measurable difference in the two arterial pressures, refuting the idea of a vascular control at the level of the main coeliac artery. Thus, in the sea raven, the adrenergic tonus affecting the visceral vasculature presumably acts at the arteriolar level.Sea ravens encouraged to exercise increased theirjaz by 64%; 32% through HR and 25% through stroke volume. The increase injaz during encouraged exercise was sufficient to produce an elevation of both Pva and Pda, despite an increase of systemic vascular conductance, β-adrenoceptor blockade with sotalol, however, severely impaired the increase injaz during exercise, and the change in Pda was reversed.During rest there were both an adrenergic and a cholinergic tonus affecting the HR, as revealed by the effects of injected pharmacological antagonists. Swimming activity decreased the cholinergic tonus, while the adrenergic tonus increased.

The effect of decerebration and anesthesia on the reflex responses to hypoxia in catfish

The ventilatory and cardiovascular responses of conscious, decerebrate, and anesthetized spontaneously breathing (ASB) catfish (Ictalurus punctatus) were measured at three different water O2 tensions [Formula: see text] to determine the advantages and limitations associated with each experimental preparation. Ventilation of the decerebrate and ASB catfish was assisted to maintain arterial [Formula: see text] levels and acid–base balance at values similar to those of conscious fish. All groups exhibited decreased heart rate (fh) and increased dorsal aortic blood pressure (PDA), and increased either ventilatory rate (fg), opercular pressure (POP), or both during hypoxia. Conscious catfish were extremely sensitive to outside disturbances and responded with transient bradycardia and apnea. The fg of decerebrate fish was consistently high and was little affected by changes in [Formula: see text]. Altered ventilation after decerebration may be due to interference with suprapontine structures involved in the control of ventilation. Unlike conscious fish, both decerebrate and anesthetized fish had maximal heart rates in normoxia and responded to hyperoxia by reducing fh. Anesthesia produced a relative tachycardia and attenuated the hypoxic bradycardia of ASB catfish, but had little effect on ventilatory reflex responses to hypoxia.

Hormone studies in Myxine glutinosa: effects of the eicosanoids arachidonic acid, prostaglandin E1, E2, A2, F2 alpha, thromboxane B2 and of indomethacin on plasma cortisol, blood pressure, urine flow and electrolyte balance.

Hagfish, Myxine glutinosa, were used in an investigation of the possible effects of various eicosanoids and the prostaglandin synthetase inhibitor indomethacin, on cortisol production, blood pressure control, urine flow and electrolyte balance. Cortisol levels in plasma of untreated control animals and plasma from animals 1 h following injection of 50 micrograms kg-1 prostaglandin E1, E2, A2, F2 alpha TXB2 and indomethacin were not detectable. However, plasma cortisol levels rose to between 10 and 26 pg ml-1 1 h following injection of either 50 micrograms kg-1 arachidonic acid or prostaglandin E2. This rise was similar in magnitude to that produced 1 h following administration of 50 micrograms kg-1 porcine ACTH. The resting dorsal aortic blood pressure of between 3.50 and 3.75 mmHg was reduced on average by 50% for 12-15 min when animals received 10 micrograms kg-1 arachidonic acid, prostaglandin E1, E2, A2, and TXB2 and was effectively reduced to zero for 20 min or more following 50 micrograms kg-1 of these eicosanoids. Similar doses of prostaglandin F2 alpha, however, evoked an increase in blood pressure (19-33%) whilst indomethacin was without effect. Control measurements of urine flow in Myxine were estimated to be between 540 and 660 microliters h-1 kg-1. There was a marked reduction in urine output following the arterial vasodepression induced by arachidonic acid, prostaglandin E1, E2, A2 and TXB2 in doses of 10 micrograms kg-1, an effect which became even more pronounced following injection of 50 micrograms kg-1 quantities, leading in some cases to complete anuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of adrenergic control of dorsal aortic blood pressure in the resting eel, Anguilla australis

AbstractDorsal aortic and cardinal venous blood pressures, dorsal aortic blood flow, and heart rate were measured in different combinations in conscious unrestrained eels (Anguilla australis). One group of animals was treated with either bretylium (10 mg.kg−1) or saline vehicle and dorsal aortic blood pressure and heart rate were monitored for the next 6 days. Two other groups were treated with phentolamine (5 mg.kg−1) and either dorsal aortic blood pressure and heart rate, or dorsal aortic blood flow and venous pressure monitored for 6 hr. In vivo treatment with either bretylium of phentolamine produced effective blockade of the α‐adrenoceptor‐mediated vasoconstriction of stimulated saline‐perfused trunk preparations; however, neither drug had no lasting effects on arterial blood pressure. In addition, phentolamine had no lasting effects on venous blood pressures or dorsal aortic blood flow. It is concluded that, in the resting eel, systemic vascular resistance is not normally under adrenergic control.

Hemodynamic, renal, and steroidogenic actions of prostaglandins E 1, E 2, A 2, and F 2α in European eels

Seawater-adapted eels were implanted with both venous and arterial cannulae and catheterised. Prostaglandin in 0.9% glucose saline was given either by 10 μl injection or by infusion (40 ng/min) while blood pressure recordings and blood samples were taken from the dorsal aorta. Glomerular filtration rates were calculated from the clearance of [ 3H]inulin, renal plasma flow from the clearance of PAH, and functional tubular mass from measurements of glucose reabsorption maxima (TmG). Cortisol levels were measured by radioimmunoassay. Injections of prostaglandin E 1, E 2, and A 2 (0.01–10 ng/kg body wt) induced transient reductions in dorsal aortic blood pressure whilst concentrations of between 10 and 100 ng/kg body wt caused both prolonged vasodepression and glomerular antidiuresis, with decreased TmG and CPAH. Fractional excretion of electrolytes remained unchanged. Doses of 10–50 μg/kg body wt caused an initial glomerular diuresis, increased TmG and CPAH but were without effect on the fractional excretion of the filtered load. This diuretic action was followed by a longer period of antidiuresis. The vasodepression during 24 hr prostaglandin infusion became less severe after an initial 2-hr period, indicating a degree of tachyphylaxis. Prostaglandin F 2α in doses of 10–50 μ/kg body wt was slightly vasopressor but with no obvious effect on kidney function. All prostaglandins so far used, given either by infusion or injection caused a significant increase in cortisol production. These results suggest that prostaglandins may play similar roles throughout a range of vertebrates.

Antidiuretic and cardiovascular actions of prostaglandin E 2 in the rainbow trout Salmo gairdneri

The renal and cardiovascular actions of intravenous injection or infusion of prostaglandin E 2 (PGE 2) have been investigated in the anaesthetised rainbow trout, Salmo gairdneri. Amounts of 1–2500 ng PGE 2/kg body wt had a potent vasodilatory action and caused rapid dose-related decreases in dorsal aortic blood pressure. Intravenous infusion of PGE 2 was associated with a secondary tachycardia and vasoconstriction. Injection of PGE 2 resulted in transient dose-related decreases of urine production. Infusion of PGE 2 at 200 ng/min/kg rapidly decreased glomerular filtration rates by reducing the populations of filtering nephrons and later by increasing the renal tubular water reabsorption. The possible endocrine systems which may be involved in the renal responses to PGE 2 are discussed.

Blood oxygenation in shortfin eels during swimming and hypoxia: Influence of the root effect

Abstract Blood samples were withdrawn from dorsal aortic cannulae in shortfin eels before, during, and after acute exposure to hypoxia and to forced swimming. Both hypoxia (PIO2 < 40 mm Hg) and forced swimming at 24 cm s‐1 abolished apnoeic periods and increased ventilation. The fall in PaCO2with hyperventilation, raised pH and thus increased the oxygen carrying capacity of arterial blood. The Root effect influences shortfin eel blood up to pH 8.0, at 17°C and has an effect on arterial oxygen content. It cannot be responsible for all of the increased oxygen content during swimming and in recovery from swimming and hypoxia; ventilatory and/or circulatory changes must account for the rest. Hypoxia, but not swimming, produced a rise in dorsal aortic blood pressure. The bradycardia of hypoxia was deeper than that which accompanies apnoeic periods in air‐saturated water.

Evidence for biorhythmicity from the preoptic nucleus of the rainbow trout Salmo gairdnerii under freely swimming conditions—An electrophysiological study

1. 1. This study describes a technique which allows continuous recording of MUA (Multiple Unit Activity), from the NPO (Preoptic Nucleus), DAP (Dorsal Aortic blood Pressure) and ECG (Electrocardiogram) in freely swimming rainbow trout. 2. 2. From the 21 trout tested, six trout (29%) clearly showed rhythmic patterns of MUA during the five post-operative days (D 2–D 6). 3. 3. The mean length of rhythmic MUA was about 18hr (range 6–33 hr) among the six trout during the recording days. Periodic MUA occurred approximately eight times/hr and lasted about 2 min. The maximal frequency of discharges was 20–30 spikes per sec. 4. 4. No change occurred in the mean level of blood pressure from the first operative day to the following post-operative days, where rhythmic MUA appeared or reappeared. 5. 5. These results demonstrate the existence of biorhythmicity within the NPO of freely swimming trout and suggest parallel oscillations in neurohormones secretion.

D- And l-isoprenaline have different effects on adrenoceptors in the systemic vasculature of the cod, Gadus moruha

1. The effects of d- and l-isoprenaline on systemic vascular adrenoceptors of the cod was studied using blood pressure recording from conscious cod in vivo and isolated coeliac artery strip preparations in vitro. 2. Experiments with isolated artery preparations demonstrated that the d-, but not the l-isomer of isoprenaline acts as an α-adrenoceptor antagonist. 3. A dose-dependent reduction of ventral and dorsal aortic blood pressures together with a dosedependent increase in the heart rate could be produced by injection of l-isoprenaline. d-Isoprenaline, on the other hand, had no effect on the blood pressures or heart rate except in the highest dose injected. 4. The results show an α-adrenoceptor blocking capacity of d-isoprenaline in the cod. The effect of l-isoprenaline on the blood pressure supports the idea that the hypotensive effect of dl-isoprenaline seen in previous studies of the cod may be attributed to an effect of the l-isomer on β -adrenoceptors mediating vasodilation of the cod systemic vasculature.

Vascular And Renal Actions Of Salmon Calcitonin In Freshwater- and Seawater-Adapted European Eels (Anguilla Anguilla)

ABSTRACT When freshwater eels were given either 5 or 15 i.u. calcitonin kg−1 body weight, there was an increase in dorsal aortic blood pressure as well as a rise in urine volume, glomerular filtration rate and electrolyte excretion rate, 1 h after injection. None of these changes was shown by seawater-adapted eels. When freshwater-adapted eels received 15 i.u. calcitonin kg−1 body weight there were significant changes in plasma electrolyte levels, again a response not shown by seawater-adapted fish. These changes occurred in 1 h after the injection of hormone, during which time plasma levels of sodium, chloride and calcium fell whilst plasma potassium levels increased. At no time within the first hour were there changes in the relative handling of electrolytes. However, seawater-adapted eels showed hypercalcaemia and a reduced relative calcium clearance 3 h after receiving 15 i.u. calcitonin kg−1 body weight.

Cardiovascular events associated with spontaneous apnea in the Australian short‐finned eel, Anguilla australis

AbstractHeart output, arterial pressures, and buccal pressure were measured in conscious, unrestrained eels (Anguilla australis). The branchial ventilatory pattern comprised alternating periods of eupnea and apnea. The transition from eupnea to apnea was always associated with significant decreases in ventral aortic blood pressure (−20%), dorsal aortic blood pressure (−16%), ventral aortic blood flow (−39%) and heart rate (−27%), and a significant increase in systemic vascular resistance (+39%). Although there were, significant decreases in cardiac stroke volume in some animals, heart output was primarily determined by heart rate. The rapidity of the transition to apnea and the occasional occurrence of Mayer waves in the circulation of A. australis is considered as evidence in favour of the neural regulation of systemic vascular resistance.

Developmental hemodynamic changes in the chick embryo from stage 18 to 27.

We report the hemodynamic parameters of stage 18, 21, 24, and 27 chick embryos (from 3 to 5 days of incubation). Dorsal aortic blood velocity and mean vitelline artery blood pressure are measured with a 20 MHz pulsed-Doppler meter and servo-null pressure system respectively. We also measure heart rate, dorsal aortic diameter and embryo weight of each developmental stage. From these data, we calculate mean dorsal aortic blood flow, mean dorsal aortic blood flow per cardiac cycle, mean dorsal aortic blood flow per milligram embryo weight, vascular resistance and cardiac work. Blood flow increases geometrically with each embryo stage but remains constant when normalized for embryo weight. Mean arterial pressure increases linearly and vascular resistance decreases geometrically. Cardiac work increases in proportion to embryo weight. These results define the parameters of normal hemodynamic function during early embryonic development.

Respiratory, Ventilatory, Acid-Base And Ionoregulatory Physiology Of The White Sucker Catostomus Commersoni: The Influence Of Hyperoxia

ABSTRACT Blood gases, acid-base status, plasma ions, respiration, ventilation and cardiovascular function were measured in white suckers, using standard cannulation methods. Basic respiratory parameters under normoxia were compared to those in the active, pelagic rainbow trout and in other benthic teleosts. Sustained environmental hyperoxia (350-550 torr) increased arterial O2 (102-392 torr) and venous O2 (17-80 torr) tensions so that blood O2 transport occurred entirely via physical solution. Dorsal aortic blood pressure and heart rate fell, the latter due to an increase in vagal tone. Ventilation volume declined markedly (by 50%) due to a decrease in ventilatory stroke volume, but absolute O2 extraction rose so that O2 consumption was unaffected. While the preceding effects were stable with time, arterial and venous CO2 tensions approximately doubled within 4 h, and continued to increase gradually thereafter. This CO2 retention caused an acidosis (7·993-7·814) which was gradually compensated by an accumulation of plasma [HCO3–]. However, even after 72 h, arterial pH remained significantly depressed by 0·10 units. The gradual rise in plasma [HCO3–] was accompanied by a progressive fall in both [Na+] and [Cl–] ; [K+] and [Ca2+] remained unchanged. The responses of the sucker to hyperoxia are compared to those of the rainbow trout.