A COMPARISON OF THE CARDIOVASCULAR EFFECTS OF BIOGENIC AMINES AND THEIR PRECURSORS IN NEWBORN AND ADULT DOGS

¹ Departments of Pharmacology, Internal Medicine and Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio

There is relatively little information regarding the cardiovascular effects of the biogenic amines in newborn animals. In the present study the pressor and chronotropic responses to i. v. injections of norepinephrine, histamine, 5-hydroxytryptamine, their respective precursors and tyramine were compared in vagotomised, 1- to 2-week-old puppies and adult dogs. Norepinephrine and its precursors produced increases in mean arterial pressure and heart rate in the newborns which were proportionately the same as those observed in the adults. Similarly the potency ratios of norepinephrine/dopamine/dopa, as reflected in the above parameters, were the same in both age groups. In addition, the time courses of the cardiovascular responses to dopamine, dopa and tyramine were generally equivalent in the newborn and adult dogs. Histamine produced a depressor response, whereas 5-hydroxytryptamine generally elicited a biphasic effect on mean arterial pressure in both groups of dogs. It is concluded that the circulatory alpha and beta adrenergic receptor systems in the newborn dog are quantitatively similar to the adult. The data also indicate that the cardiovascular system of the newborn dog is as sensitive as that of the adult to the effects of the other biogenic amines and their precursors.