Cardiovascular Reactivity of Neonatal and Adult Sheep to Autonomic Stimuli during Adrenergic Depletion

Abstract

The cardiovascular responses of the neonatal and adult sheep to autonomic agonists and antagonists were studied in the resting state and following adrenergic neuronal depletion with reserpine. Both the neonates and adults showed similar supersensitivity of the effector system of the peripheral circulation to alpha adrenergic stimulation with catecholamines. In addition, the neonates exhibited supersensitivity of the myocardial effector system to β-adrenergic stimulation. Unusual finding was a marked supersensitivity of the heart and peripheral circulation to cholinergic receptor blockade with atropine, the mechanisms of which are as yet unclear.