Adrenal catecholamines during and following hypoxia in neonatal rats.

The synthesis and content of adrenal catecholamines during hypoxia (6% O2) and the following recovery period were investigated in 4-day old rats. Adrenal catecholamine synthesis, as indicated by the dopamine content of the glands, increased significantly during hypoxia. During hypoxia a significant decrease in the adrenal noradrenaline but not adrenaline content was noted. In the recovery period following 30 min of hypoxia the noradrenaline level was rapidly restored to the control value. The results show that hypoxia causes increased catecholamine synthesis in the immature rat adrenal gland, presumably mediated by an increased tyrosine hydroxylase activity induced via the splanchnic nerves. In the neonate rat hypoxia seems to stimulate the release of a larger proportion of noradrenaline than adrenaline from the adrenal glands when compared to the adult animal.