Effect of prostaglandins on bradykinin-induced visceral-cardiac reflexes.

We examined the effect of prostaglandins on the reflex cardiovascular response to bradykinin applied to the abdominal organs of anesthetized cats. Bradykinin (10 micrograms/ml) was applied to the serosal surface of the stomach, gallbladder, or jejunum before and after injection of indomethacin (2-10 micrograms/ml iv) and after application of 1 microgram/ml of prostaglandins E1, E2, or F2 alpha (PGE1, PGE2, PGF2 alpha) or prostacyclin (PGI2). In six cats, stimulation of the stomach with bradykinin significantly increased mean arterial pressure (MAP) by 37 +/- 5 (SE) mmHg and maximal dP/dt by 633 +/- 101 mmHg/s.

Bradykinin-induced chemoreflexes from skeletal muscle: implications for the exercise reflex.

We examined the cardiovascular response to bradykinin stimulation of skeletal muscle afferents and the effect of prostaglandins on this response. Intra-arterial injection of 1 microgram bradykinin into the gracilis muscle of cats reflexly increased mean arterial pressure by 16 +/- 2 mmHg, left ventricular end-diastolic pressure by 1.6 +/- 0.

Extracardiac and coronary vascular effects of digitalis.

The administration of digitalis glycosides causes a variety of extracardiac effects. In both normal human subjects and in other species, digitalis increases smooth muscle tone of resistance and capacitance vessels. The vasoconstriction is mediated, in part, by a direct action of these glycosides on smooth muscle and, in part, by an increase in alpha-adrenergic tone.

Cardiovascular effects of haemorrhagic shock in spleen intact and in splenectomized dogs.

Cardiac performance was evaluated during haemorrhagic shock in 27 dogs with spleens intact, 24 splenectomized, and 23 splenectomized transfused dogs that were given a volume of packed red blood cells simulating splenic contraction. Contractile changes were evaluated by calculating dP/dt at 20 mmHg developed pressure (dP/dt DP20), and by relating stroke work to left ventricular end-diastolic volume measured by biplane cinefluorography. Although heart rate increased comparably during early shock, cardiac output, stroke volume, maximal dP/dt, dP/dt DP20, and arterial blood pressure decreased more in splenectomized and splenectomized transfused dogs than in those with spleens intact.

Cardiac receptors: their function in health and disease.

Cardiac receptors include both mechanically and chemically sensitive receptors located in atria and in ventricles. Atrial receptors innervated by myelinated vagal afferent fibers reflexly regulate heart rate and intravascular volume. On the other hand, stimulation of ventricular receptors can cause either reflex bradycardia and hypotension or, alternatively, excitation of the cardiovascular system.

Effects of bradykinin and capsaicin on endings of afferent fibers from abdominal visceral organs.

Stimulation of sensory endings in abdominal visceral organs with capsaicin or bradykinin reflexly increases heart rate, blood pressure, and myocardial contractility through afferent pathways in splanchnic nerves. To determine the afferent fiber types stimulated, we recorded impulses in the right splanchnic nerve in 12 anesthetized cats after either injecting capsaicin (50-200 micrograms) or bradykinin (6.5-20 micrograms) into the descending thoracic aorta or applying pledgets soaked with these chemicals to a visceral organ.

Chemically induced cardiovascular reflexes arising from the stomach of the cat.

We examined the potential for cardiovascular reflexes caused by the application of either bradykinin or capsaicin to the serosal or mucosal surface of the stomach. After application to the serosa, bradykinin (10 micrograms/ml) evoked increases in mean arterial pressure of 12 +/- 2 mmHg, heart rate of 5 +/- 1 beats/min, left ventricular dP/dt (at 40 mmHg developed pressure) of 305 +/- 54 mmHg/s and systemic vascular resistance of 0.04 +/- 0.

Oxygen consumption and hemodynamic responses during graded treadmill exercise in the dog.

A description is given of a technique that provides a relatively simple means by which O2 consumption and hemodynamic variables can be measured in exercising dogs. We used a multistage submaximal treadmill test to study the responses of 10 foxhounds to dynamic exercise. They were also studied during maximal treadmill exercise.

Static contraction of hindlimb muscles in cats reflexly relaxes tracheal smooth muscle.

Static contraction of skeletal muscle is associated with increased ventilation. Although chemical stimulation of afferents from skeletal muscle causes relaxation of tracheal smooth muscle, it is not known if skeletal muscle contraction also causes tracheal relaxation. Therefore, in 10 chloralose-anesthetized cats, I examined the hemodynamic and tracheal smooth muscle responses to hindlimb skeletal muscle contraction induced by stimulating the L7 and S1 ventral roots.

Reflex regional vascular responses during passive gastric distension in cats.

The increase in systemic vascular resistance during gastric distension in cats may result from variable vasomotor responses in several parallel regional vascular beds. Accordingly, in 23 anesthetized cats the stomach was passively distended with a balloon while systemic hemo-dynamics were monitored. Regional vascular responses were determined during control periods and during gastric distension either by injection of radioactive microspheres (15 cats) or by constant perfusion of vascularly isolated organs (8 cats).

Localization of the cells of origin for primary afferent fibers supplying the gallbladder of the cat.

Horseradish peroxidase was utilized to study the distribution of afferent fibers from the gallbladder in cats. The afferent cell bodies were found in the nodose ganglion and T4 to L1 dorsal root ganglia.

Stimulation of pancreatic afferents reflexly activates the cardiovascular system in cats.

Chemical stimulation of afferents from the stomach and gallbladder has been shown reflexly to activate the cardiovascular system. It is not known, however, whether stimulating afferents from the pancreas evoke similar reflex activity. Therefore we recorded the cardiovascular responses in cats anesthetized with methoxyflurane, while we applied capsaicin (200 micrograms/ml) and bradykinin (0.

Stimulation of splanchnic afferents reflexly relaxes tracheal smooth muscle in dogs.

Although chemical stimulation of abdominal visceral afferents has been shown to reflexly increase cardiovascular and ventilatory function, the effect of stimulating these afferents on airway smooth muscle is unknown. Therefore, we recorded transverse smooth muscle tension from an innervated segment of trachea in chloralose-anesthetized dogs while we topically applied capsaicin (200 micrograms/ml) and bradykinin (0.01-10 micrograms/ml) to the serosal surfaces of the stomach, small intestine, and gallbladder.

Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats.

Static contraction of the hindlimb muscles, induced by electrical stimulation of the ventral roots, reflexly increases arterial blood pressure and heart rate. Although stimulation of groups III and IV muscle afferents is believed to cause these reflex increases, the responses of these afferents to a level of static contraction that increases arterial pressure have not yet been determined. Therefore, in barbiturate-anesthetized cats, afferent impulses arising from endings in the gastrocnemius muscle were recorded from the L7 or S1 dorsal roots, while the cut peripheral end of the L7 ventral root was stimulated.

Bradykinin-induced cardiovascular reflexes from the gallbladder in cats.

To determine whether bradykinin, an algesic substance produced in certain inflammatory states, can stimulate gallbladder receptors to cause significant cardiovascular reflexes, we applied this agent to the serosal surface of the gallbladder in cats anesthetized with methoxyflurane. As a control, bradykinin was also applied to the serosal surface of the liver surrounding the gallbladder. Significant cardiovascular reflexes were obtained from the gallbladder in an increasing, dose related fashion over a range of concentrations from 50 pg/ml to 100 micrograms/ml of bradykinin.

Cardiovascular reflexes arising from the gallbladder of the cat. Effects of capsaicin, bradykinin, and distension.

We have studied the cardiovascular responses which can be evoked when the gallbladder is stimulated pharmacologically or mechanically. To determine the potential for reflex cardiovascular activation, we applied capsaicin, a selective thin-fiber agonist, to the serosal surface of the gallbladder. This algesic substance evoked cardiovascular responses which included increases in mean arterial pressure (MAP) by 14%, heart rate (HR) by 3%, left ventricular dP/dt at 40 mm Hg developed pressure (dP/dt DP40) by 14%, and systemic vascular resistance (SVR) by 19%.

Sympathoadrenal mechanisms in hemodynamic responses to gastric distension in cats.

There is presently little information on the efferent mechanisms responsible for the reflex cardiovascular activation during passive gastric distension. Therefore, 40 cats anesthetized with alpha-chloralose were studied with passive gastric balloon distention before and during 1) two repeated gastric distensions, 2) beta-adrenergic blockade with propranolol, 3) alpha-adrenergic blockade with phentolamine, or 4) bilateral adrenalectomy. Before and during each distension mean arterial pressure, heart rate, cardiac output, rate of rise of left ventricular pressure (dP/dt) at 40 mmHg developed pressure and calculated systemic vascular resistance were determined.

Reflex relaxation of tracheal smooth muscle by thin-fiber muscle afferents in dogs.

Although the reflex cardiovascular and ventilatory responses evoked by stimulation of groups III and IV muscle afferents have been extensively investigated, less is known about the effects of stimulation of these afferents on airway caliber. Therefore, in 11 chloralose-anesthetized dogs, we recorded transverse smooth muscle tension from an innervated segment of the trachea, while we stimulated groups III and IV muscle afferents with capsaicin and bradykinin. Injection of both substances into the arterial supply of the skinned hindlimb evoked dose-dependent decreases in tracheal tension, whereas injection into the femoral vein either increased tension or had no effect on it.

Reflex cardiovascular depression induced by capsaicin injection into canine liver.

Capsaicin was injected into the portal circulation of 29 dogs after a blood delay pathway was constructed between the liver and right heart, through which capsaicin-contaminated blood could be replaced while systemic hemodynamics were maintained constant. Capsaicin (500 micrograms) rapidly decreased left ventricular systolic pressure (-10%), mean arterial pressure (-12%), heart rate (-4%), renal vascular resistance (-7%), maximal rate of left ventricular pressure rise (dP/dtmax) (-12%), and dP/dt at 25 mmHg developed left ventricular pressure (-15%) in animals with paced hearts. Left ventricular end-diastolic pressure did not change.

Effects of capsaicin and bradykinin on afferent fibers with ending in skeletal muscle.

Capsaicin, injected into the arterial supply of the skinned hindlimb of dogs, evokes reflex increases in cardiovascular function. Moreover, the cardiovascular reflexes evoked by capsaicin are very similar to those evoked by static exercise. The afferent fibers initiating these reflex increases have not been identified electrophysiologically, although their endings are believed to be located in skeletal muscle.

Total plasma creatinine: an accurate measure of total striated muscle mass.

Creatinine is a metabolite unique to striated muscle. Measurement of 24-h urinary creatinine excretion is an established method for estimating striated muscle mass. However, accurate assessment of urinary creatinine excretion is often impractical.

Static exercise in anesthetized dogs, a cause of reflex alpha-adrenergic coronary vasoconstriction.

The coronary blood flow and vascular resistance responses to static hindlimb exercise were studied in 11 anesthetized dogs after beta- and combined alpha- and beta-adrenergic blockade to determine if this stress causes coronary vasoconstriction. After beta-blockade static exercise increased the blood pressure and double product, but decreased the right and left ventricular (LV) coronary blood flow and increased the coronary vascular resistance. These vascular changes primarily occurred in the epicardial and mid-myocardial but not the endocardial layers of the LV.

Chronic training with static and dynamic exercise: cardiovascular adaptation, and response to exercise.

To determine the acute and chronic effects of static and dynamic exercise upon the cardiovascular system, two groups of athletes were studied and compared to untrained control individuals. Thus, 12 long distance runners (LDR) and 17 competitive weight lifters (CWL) were compared to 10 light controls (LC) and 14 heavy controls (HC). The echocardiographically measured left ventricular mass (LVM) was shown to be increased in both groups of athletes.

Cardiovascular reflexes elicited by passive gastric distension in anesthetized cats.

Hemodynamic responses to passive gastric distension were examined in alpha-chloralose anesthetized cats. Gastric balloons were distended with 37 degrees C fluid at slow (50 ml/min) and rapid (250 ml/min) infusion rates before and after laparotomy. Passive gastric distension at the slow infusion rate significantly (P less than 0.