Effects of acute hypoxia on neonatal rat brain: Regionally selective, long-term alterations in catecholamine levels and turnover

Abstract

Neonatal rats were exposed to 2 hr of hypoxia (7% O 2) on the day after birth and examined for effects on development of noradrenergic and dopaminergic systems. Measurements were made of transmitter levels and turnover, the latter a biochemical index of neuronal activity. Hypoxia had a regionally selective effect, characterized by a long-lasting increase in turnover of norepinephrine and dopamine in midbrain and brainstem, with little or no effect in cerebral cortex or cerebellum. The effects of hypoxia were exacerbated when peripheral α-adrenergic receptors were blocked with phenoxybenzamine during the hypoxic exposure; in this case, the same abnormalities were then seen in the cerebral cortex as well. Thus, the release of peripheral catecholamines during the hypoxic insult, and their actions at α-adrenergic receptors, may play a role in protecting the neonatal nervous system from hypoxia-induced alterations.