LONG-TERM IMPAIRMENT IN THE NEUROCHEMICAL ACTIVITY OF THE SYMPATHOADRENAL SYSTEM AFTER NEONATAL HYPOXIA IN THE RAT

The study evaluates the long-term effect of neonatal hypoxia on the ne urochemical activity of the sympathoadrenal system in the rat. One-day -old male pups were exposed to hypoxia (10% O-2) for 6 d and thereafte r reared under normoxia. Neonatal hypoxia reduced the body weight of 3 - and 8-wk-old rats and did not change the blood pressure at 6 wk of a ge. In sympathetic ganglia, the content and/or turnover rates of norep inephrine were reduced in neonatal-hypoxic rats of 3 and 8 wk of age, but the content and turnover rates of dopamine were unaltered. The eff ect was not dependent on the type of ganglion. In the superior cervica l ganglion, neonatal hypoxia had a selective effect on the type of cat echolamine (dopamine versus norepinephrine), thus suggesting a selecti ve-altered maturation of noradrenergic neurons, but presumably not of the dopaminergic small, intensely fluorescent cells. A long-term defic iency in adrenal activity was the consequence of neonatal hypoxia, as shown by the decrease in the content and turnover rate of dopamine. Ne onatal hypoxia elicited a long-term decrease in the content and turnov er rates of norepinephrine in heart and lungs but failed to induce a s ignificant effect in kidneys. However, this effect was not tissue-spec ific. Data provide evidence that a hypoxic episode occurring during a critical period of development in the rat induces a long lasting decre ase in the neurochemical activity of the sympathoadrenal system. These results are discussed in terms of their implications for human pathol ogy.