ARCHITECTURAL ALTERATIONS IN RAT CEREBRAL MICROVESSELS AFTER HYPOBARIC HYPOXIA

We performed 3-dimensional studies of vascular casts of the micro vasc ulature of the cerebral cortex of rats that were exposed to three week s of hypobaric hypoxia and of control rats. Scanning electron microsco py of the casts gave the qualitative impression of increased vasculari ty of the cerebral cortex, particularly the deeper layers, in hypoxic rats. Quantitative analysis of capillary segment lengths revealed a si gnificant shift in the frequency distribution to longer lengths (from 77 +/- 8 to 90 +/- 14 mu m) in the deep, but not in the superficial, l ayers of the cerebral cortex of hypoxic rats. These findings agree wit h previous results reporting increased capillary density in the brain after exposure to prolonged hypobaric hypoxia and suggest that capilla ry segment elongation plays a role in the increased capillary density in the deeper layers of the cerebral cortex.