Hyperoxia: effects on the vascularization of the developing central nervous system.

Litters of experimental and control hamsters were killed on postnatal days 3, 4, 7, 14, 21, and 28 following 7 days of exposure to 85% oxygen at normabaric pressure. Using analysis of variance (ANOVA), light microscopy quantitation of the number of blood vessel profiles per unit area in the region of the frontal cerebral cortex demonstrated that the combined effect of treatment and age on the animals produced a highly statistically significant difference (p less than 0.001) in the numbers of blood vessel profiles. The statistically separated treatment effect was also found to be significant (P less than 0.05). The data are summarized in Table 1. Ultrastructural analysis of animals exposed to oxygen only, i.e., killed without being returned to the normal air environment, demonstrated severe signs of vaso-obliteration. Animals which were returned to a normal atmosphere following 7 days in oxygen showed a progressive decrease in the signs of vaso-obliteration. This present study demonstrated the marked similarity between the effects of hyperoxia on he CNS and on the neuro-retina.