Asymmetry in the control of cardiac performance by dorsomedial hypothalamus

2013 ◽  
Vol 304 (8) ◽  
pp. R664-R674 ◽  
Author(s):  
Carlos Henrique Xavier ◽  
Mirza Irfan Beig ◽  
Danielle Ianzer ◽  
Marco Antônio Peliky Fontes ◽  
Eugene Nalivaiko
Keyword(s):  
Heart Rate ◽  
Cardiac Contractility ◽  
Left Ventricular Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Inotropic Effects ◽  
Dorsomedial Hypothalamus ◽  
Anesthetized Rats ◽  
Ectopic Beats

Dorsomedial hypothalamus (DMH) plays a key role in integrating cardiovascular responses to stress. We have recently reported greater heart rate responses following disinhibition of the right side of the DMH (R-DMH) in anesthetized rats and greater suppression of stress-induced tachycardia following inhibition of the R-DMH in conscious rats [both compared with similar intervention in the left DMH (L-DMH)], suggesting existence of right/left side asymmetry in controlling cardiac chronotropic responses by the DMH. The aim of the present study was to determine whether similar asymmetry is present for controlling cardiac contractility. In anesthetized rats, microinjections of the GABAA antagonist bicuculline methiodide (BMI; 40 pmol/100 nl) into the DMH-evoked increases in heart rate (HR), left ventricular pressure (LVP), myocardial contractility (LVdP/d t), arterial pressure, and respiratory rate. DMH disinhibition also precipitated multiple ventricular and supraventricular ectopic beats. DMH-induced increases in HR, LVP, LVdP/d t, and in the number of ectopic beats dependent on the side of stimulation, with R-DMH provoking larger responses. In contrast, pressor and respiratory responses did not depend on the side of stimulation. Newly described DMH-induced inotropic responses were rate-, preload- and (largely) afterload-independent; they were mediated by sympathetic cardiac pathway, as revealed by their sensitivity to β-adrenergic blockade. We conclude that recruitment of DMH neurons causes sympathetically mediated positive chronotropic and inotropic effects, and that there is an asymmetry, at the level of the DMH, in the potency to elicit these effects, with R-DMH > L-DMH.

Reflex cardiac effects of local cutaneous cold exposure in dogs

1980 ◽  
Vol 239 (1) ◽  
pp. H114-H120
Author(s):  
J. F. Borgia ◽  
S. M. Horvath
Keyword(s):  
Heart Rate ◽  
Cardiac Contractility ◽  
Oxygen Demand ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Myocardial Oxygen Demand ◽  
Adrenergic Blockade ◽  
Stroke Index ◽  
Ventricular Contractility ◽  
Cold Stimulation

Cardiovascular responses initiated by local cutaneous cooling were evaluated in 16 anesthetized dogs of which 8 were pretreated with propranolol. Heart rate, cardiac index (CI), and indices of ventricular contractility were significantly elevated in untreated animals during cold stimulation. Myocardial oxygen uptake (MVo2) and left ventricular work (LVW) were also increased, and cardiac mechanical efficiency was significantly reduced. Total peripheral vascular resistance remained unchanged. In the propranolol group, heart rate decreased by 12 beats/min, but CI was maintained constant during cold by a rise in stroke index. Left ventricular dP/dtmax was reduced and ventricular preload elevated, but LVW, MVo2, and cardiac efficiency were unchanged. These data indicate that local cutaneous cooling increases myocardial oxygen demand by reflexly elevating heart rate and cardiac contractility rather than by increasing cardiac afterload. The response is completely eliminated by beta-adrenergic blockade. The significance of these observations in regard to the cold-intolerant individual with coronary disease is discussed.

Effects of alpha-adrenergic blockade on cardiovascular responses to static exercise in cats

1986 ◽  
Vol 250 (1) ◽  
pp. R1-R4
Author(s):  
T. G. Waldrop ◽  
M. Bielecki ◽  
W. J. Gonyea ◽  
J. H. Mitchell
Keyword(s):  
Systolic Pressure ◽  
Left Ventricular Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Static Exercise ◽  
Ventricular Systolic Pressure ◽  
Pressure Transducers ◽  
Adrenergic Mechanism ◽  
Alpha Blockade

Static exercise performed by conscious cats elicits increases in heart rate (HR), left ventricular systolic pressure (LVSP), and the maximal rate of left ventricular pressure development [LV(dP/dt)max]. The increased HR is mediated primarily by withdrawal of parasympathetic tone, whereas a beta-adrenergic mechanism is responsible for the LV(dP/dt)max increase. In the present study the cardiovascular responses to static exercise in awake cats was recorded before and after alpha-adrenergic blockade. Pressure transducers were implanted into the left ventricle of cats who had been trained operantly to perform static exercise. Significant increases in LVSP, LV(dP/dt)max and HR occurred in all cats during static exercise before blockade. In contrast, alpha-adrenergic blockade (phentolamine, 2.5 mg/kg iv) abolished the exercise-induced increase in LVSP but did not prevent increases in HR and LV(dP/dt)max. The cats performed fewer exercise bouts per day during alpha-blockade than when unblocked. We conclude that an alpha-adrenergic mechanism mediates the increase in LVSP in response to static exercise in conscious cats.

Similarity of cardiovascular responses to exercise and to diencephalic stimulation

1960 ◽  
Vol 198 (6) ◽  
pp. 1139-1142 ◽  
Author(s):  
Orville A. Smith ◽  
Robert F. Rushmer ◽  
Earl P. Lasher
Keyword(s):  
Heart Rate ◽  
Third Ventricle ◽  
Left Ventricular Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Ventricular Pressure ◽  
The Third ◽  
Stimulating Electrodes ◽  
Stimulation Of

Devices to measure left ventricular pressure, diameter and heart rate in animals with closed chests were placed on the hearts of dogs. After recovery from this operation the dogs were trained to exercise on a treadmill and the cardiovascular responses to this exercise were recorded. Stimulating electrodes were then stereotaxically placed in the diencephalon. In some dogs the electrodes were chronically implanted, and the stimulation was carried out after recovery from this second operation. In other animals stimulation was carried out immediately while they were under chloralose anesthesia. Stimulation of the H1 and H2 fields of Forel and the periventricular gray of the third ventricle resulted in cardiovascular responses similar to those which result from exercise.

Reflex sympathetic augmentation of left-ventricular inotropic state in the conscious dog

1981 ◽  
Vol 241 (6) ◽  
pp. H857-H863
Author(s):  
C. Yoran ◽  
L. Higginson ◽  
M. A. Romero ◽  
J. W. Covell ◽  
J. Ross
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Pressure Rise ◽  
Left Ventricular Pressure ◽  
Systemic Arterial Pressure ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Conscious Dog ◽  
Inotropic State ◽  
Simultaneous Decrease

Cardiac reflex responses to a series of partial inferior vena caval occlusions were studied in conscious previously instrumented dogs. Heart rate responses during the fall of systemic arterial pressure were mediated both by increased sympathetic tone and withdrawal of parasympathetic tone. Responses of the left-ventricular inotropic state, estimated from changes in left ventricular pressure rise (LV dP/dt), were studied early after release of a series of partial vena caval occlusions, and a positive linear relation between the prior fall in the systemic arterial pressure and the increase in LV dP/dt was demonstrated. Serial studies showed this effect of persist for at least 12 s beyond the reflex slowing of heart rate early after release of vena caval occlusion. The positive inotropic response was markedly attenuated by beta-adrenergic blockade and also occurred at a constant heart rate. It was present after adrenalectomy. These studies suggest that the integrated baroreceptor responses that are activated by a simultaneous decrease in the venous return and systemic arterial pressure play an important role in the regulation of left-ventricular inotropic state in the conscious dog.

The cardiovascular effect of chloroquine in anaesthetized dogs

1980 ◽  
Vol 58 (7) ◽  
pp. 836-841 ◽  
Author(s):  
O. A. Sofola
Keyword(s):  
Maximum Rate ◽  
Intact Animal ◽  
Direct Action ◽  
Cardiac Contractility ◽  
Left Ventricular Pressure ◽  
Cardiovascular Responses ◽  
Left Ventricular ◽  
Constant Flow ◽  
Sympathetic Block ◽  
Maximum Rate Of Rise

Dogs were anaesthetized with sodium pentobarbitone and the effects, on the cardiovascular system, of graded doses of chloroquine were investigated.Intravenous injection of chloroquine from 2 to 4 mg kg−1 produced significant reductions in cardiac contractility, as estimated by measuring the maximum rate of rise of left ventricular pressure, and also in vascular resistance, estimated by measuring the pressure in a femoral artery perfused at constant flow. Heart rate was reduced significantly only when a dose of 4 mg kg−1 was used.The cardiovascular responses observed in the intact animal were also present after cardiac sympathetic block with propranolol and denervation of the limb or after administration of histamine H1 and H2 receptor antagonists. This suggests that the responses were due to the direct action of chloroquine on the heart and blood vessels.

alpha-Adrenergic control of oxygen delivery to myocardium during exercise in conscious dogs

1982 ◽  
Vol 242 (5) ◽  
pp. H805-H809 ◽  
Author(s):  
G. R. Heyndrickx ◽  
P. Muylaert ◽  
J. L. Pannier
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Oxygen Delivery ◽  
Left Ventricular ◽  
Conscious Dogs ◽  
Adrenergic Blockade ◽  
Adrenergic Control

alpha-Adrenergic control of the oxygen delivery to the myocardium during exercise was investigated in eight conscious dogs instrumented for chronic measurements of coronary blood flow, left ventricular (LV) pressure, aortic blood pressure, and heart rate and sampling of arterial and coronary sinus blood. After alpha-adrenergic receptor blockade a standard exercise load elicited a significantly greater increase in heart rate, rate of change of LV pressure (LV dP/dt), LV dP/dt/P, and coronary blood flow than was elicited in the unblocked state. In contrast to the response pattern during control exercise, there was no significant change in coronary sinus oxygen tension (PO2), myocardial arteriovenous oxygen difference, and myocardial oxygen delivery-to-oxygen consumption ratio. It is concluded that the normal relationship between myocardial oxygen supply and oxygen demand is modified during exercise after alpha-adrenergic blockade, whereby oxygen delivery is better matched to oxygen consumption. These results indicate that the increase in coronary blood flow and oxygen delivery to the myocardium during normal exercise is limited by alpha-adrenergic vasoconstriction.

scholarly journals Electrophysiological effects of right and left vagal nerve stimulation on the ventricular myocardium

2014 ◽  
Vol 307 (5) ◽  
pp. H722-H731 ◽  
Author(s):  
Kentaro Yamakawa ◽  
Eileen L. So ◽  
Pradeep S. Rajendran ◽  
Jonathan D. Hoang ◽  
Nupur Makkar ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nerve Stimulation ◽  
Regional Differences ◽  
Left Ventricular Pressure ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Vagal Nerve ◽  
Vagal Nerve Stimulation ◽  
Ventricular Pressure ◽  
Electrophysiological Effects

Vagal nerve stimulation (VNS) has been proposed as a cardioprotective intervention. However, regional ventricular electrophysiological effects of VNS are not well characterized. The purpose of this study was to evaluate effects of right and left VNS on electrophysiological properties of the ventricles and hemodynamic parameters. In Yorkshire pigs, a 56-electrode sock was used for epicardial ( n = 12) activation recovery interval (ARI) recordings and a 64-electrode catheter for endocardial ( n = 9) ARI recordings at baseline and during VNS. Hemodynamic recordings were obtained using a conductance catheter. Right and left VNS decreased heart rate (84 ± 5 to 71 ± 5 beats/min and 84 ± 4 to 73 ± 5 beats/min), left ventricular pressure (89 ± 9 to 77 ± 9 mmHg and 91 ± 9 to 83 ± 9 mmHg), and dP/d tmax (1,660 ± 154 to 1,490 ± 160 mmHg/s and 1,595 ± 155 to 1,416 ± 134 mmHg/s) and prolonged ARI (327 ± 18 to 350 ± 23 ms and 327 ± 16 to 347 ± 21 ms, P < 0.05 vs. baseline for all parameters and P = not significant for right VNS vs. left VNS). No anterior-posterior-lateral regional differences in the prolongation of ARI during right or left VNS were found. However, endocardial ARI prolonged more than epicardial ARI, and apical ARI prolonged more than basal ARI during both right and left VNS. Changes in dP/d tmax showed the strongest correlation with ventricular ARI effects ( R2 = 0.81, P < 0.0001) than either heart rate ( R2 = 0.58, P < 0.01) or left ventricular pressure ( R2 = 0.52, P < 0.05). Therefore, right and left VNS have similar effects on ventricular ARI, in contrast to sympathetic stimulation, which shows regional differences. The decrease in inotropy correlates best with ventricular electrophysiological effects.

Alteration in myocardial oxygen balance during exercise after beta-adrenergic blockade in dogs

1980 ◽  
Vol 49 (1) ◽  
pp. 28-33 ◽  
Author(s):  
G. R. Heyndrickx ◽  
J. L. Pannier ◽  
P. Muylaert ◽  
C. Mabilde ◽  
I. Leusen
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Myocardial Blood Flow ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Myocardial Oxygen Consumption ◽  
Left Ventricular ◽  
Adrenergic Blockade ◽  
Oxygen Balance

The effects of beta-adrenergic blockade upon myocardial blood flow and oxygen balance during exercise were evaluated in eight conscious dogs, instrumented for chronic measurements of coronary blood flow, left ventricular pressure, aortic blood pressure, heart rate, and sampling of arterial and coronary sinus venous blood. The administration of propranolol (1.5 mg/kg iv) produced a decrease in heart rate, peak left ventricular (LV) dP/dt, LV (dP/dt/P, and an increase in LV end-diastolic pressure during exercise. Mean coronary blood flow and myocardial oxygen consumption were lower after propranolol than at the same exercise intensity in control conditions. The oxygen delivery-to-oxygen consumption ratio and the coronary sinus oxygen content were also significantly lower. It is concluded that the relationship between myocardial oxygen supply and demand is modified during exercise after propranolol, so that a given level of myocardial oxygen consumption is achieved with a proportionally lower myocardial blood flow and a higher oxygen extraction.

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