Postnatal development of catecholamines and response to hypoxia in adrenals and paraganglia of rabbits

The postnatal development of catecholamine levels in adrenals and paraganglia in newborn rabbits has been analyzed. At birth, the dominant catecholamine was noradrenaline, contributing 66% of the total catecholamine pool at day 1, 55% of which came from the paraganglia. There was a rapid postnatal increase of adrenaline, which constituted 67% of the total catecholamines at day 6 and 97% in the adult. After hypoxia at day 1, the noradrenaline levels decreased in paraganglia but not in adrenals, while adrenaline levels did not significantly change in either organ.