Effects of asphyxia on telencephalic microvessels of premature beagle pups

The authors identified alterations in the brain microvasculature of the premature Beagle pup that could be attributed to asphyxia and potentially associated with the etiology of intraventricular hemorrhage (IVH). Beagle pups were delivered by cesarean section six days before their predicted whelping date and exposed to an alternating protocol of asphyxial episodes known to produce IVH. Data from the telencephalic microvasculature at both the germinal matrix (an area susceptible to IVH) and the borderzone cerebral cortex (an area rarely involved in hemorrhage) were analyzed. The germinal matrix microvessels responded differently to asphyxia than the cortical vessels. The germinal matrix microvessels maintained junctional complexes and intraluminal microvilli, and increased in cross-sectional luminal area following asphyxia; however, total vessel cross-sectional area did not change. After the asphyxial insult, cortical microvessels no longer exhibited intraluminal microvilli and increased in both total cross-sectional area and luminal area. The number of junctional complexes in cross-sections of cortical vessels was significantly reduced due at least in part to the narrowing of the endothelial cell lateral borders. The data provide indirect evidence to substantiate vasodilation speculated to be due to an increased cerebral blood flow to telencephalic vessels (both the germinal matrix and cerebral cortex) following asphyxia. The data also suggest differential rates of maturation between germinal matrix and cortical microvessels.