Reduction of the Cardiac Response to Postganglionic Sympathetic Nerve Stimulation in Experimental Heart Failure

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Abstract
The functional significance of the reduction of the heart's norepinephrine stores which occurs in experimental heart failure was studied. The responses to right and left cardio-accelerator nerve stimulation were studied in normal dogs and in dogs with chronic congestive failure and reduced myocardial norepinephrine stores. Both the chronotropic and inotropic responses to nerve stimulation were found to be markedly reduced in the animals with congestive failure. Since the myocardium of the dogs with heart failure responded normally to exogenously administered norepinephrine, it was concluded that the norepinephrine depletion reduces the quantity of neurotransmitter released per nerve impulse. Thus, norepinephrine depletion interferes with the ability of the adrenergic nervous system to support the failing myocardium and in this manner it may intensify the congestive heart failure state.