EFFECTS OF CONTROL OF CARDIAC WORK UPON CORONARY FLOW AND O₂ CONSUMPTION AFTER SYMPATHETIC NERVE STIMULATION

Changes in cardiac transcapillary exchange with metabolic coronary vasodilation in the intact dog.

“…It seems unlikely that any previous coronary dilution studies in the working heart have been carried out at comparably low levels of sympathetic activity (which correspond to what is normally seen at rest). Since sympathetic activation increases the myocardial oxygen consumption and elevates coronary blood flow (Eckstein et al, 1950), the low sympathetic tone observed in control animals in the present study could explain our low baseline values for coronary flow, and especially their approach to the levels of flow observed in the sedated conscious dog. The delineation of the exchange characteristics of the coronary circulation in this more normal state is therefore of great interest, since any knowledge gained is new.…”

“…At the rime of these studies, aortic and coronary sinus norepinephrine values were comparable, indicating that interstitial values were of a similar magnitude (Cousineau et al, 1981). The increased norepinephrine levels will be expected to be associated, in the animals with a raised fixed rate, with a secondary potent inotropic effect (Eckstein et al, 1950, Yamaguchi et al, 1975 and further increase in metabolic demand and coronary flow due to this. Figure 3 illustrates the increase in <f> with increase in plasma norepinephrine.…”

“…Openchest dog protocols are associated with high plasma catecholamine values, even under apparently basal conditions (Yamaguchi et al, 1975), indicating an activation of the sympathetic system. Since an elevation in sympathetic tone increases myocardial metabolism (Eckstein et al, 1950), diminished degrees of capillary heterogeneity will be expected to be present in autoperfused open-chest dogs. The behavior of the microvascular bed under these circumstances will thus be expected to be more uniform than that in a baseline low metabolic activity state.…”

Effect of Cervico-Thoracic Ganglionectomy on the Adrenaline and Noradren Aline Content in the Mammalian Heart1

“…Adrenaline on the other hand apparently serves the purpose of enhancing the myocardial metabolism (24)(25)(26)(27) and increasing the cardiac rate (28)(29)(30). Both of these catechols dilate the coronary arteries (31,32).…”

“…action of noradrenaline and adrenaline (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37), and in view of the lack of evidence regarding cardiac sympathetic innervation, the experiments herein described were carried out with the express purpose of trying to establish and clarify the relationship of the various cardiac ganglia to the noradrenaline (norepinephrine) and adrenaline (epinephrine) content of mammalian heart, and further, to determine whether or not the sympathetic nerves to the heart regenerate after cardiac sympatho-ganglionectomy, and if so, how soon.…”