New model of hemorrhagic hypoxic-ischemic encephalopathy in newborn mice.

An easy and inexpensive method is reported for producing hemorrhagic brain damage in newborn mice, involving only exposure to hypoxia. One-day-old mice, Jcl:ICR strain, were subjected to a humidified 5% oxygen, 95% nitrogen mixture for 8 hours. After the hypoxic episode, 34% of newborn mice survived, 59% manifested cerebral parenchymal hemorrhage. Cortical hemorrhage could be detected in live mice; intracranial hemorrhage was observed through the thin skin and skull. Cortical hemorrhage usually affected the bilateral parietal regions symmetrically and neuronal destruction was observed in the deeper structures, as well as in the cerebral cortex. This pattern of damage was comparable to parasagittal cerebral injury in humans. The onset of cortical hemorrhage and neuropathology in these mice suggested that hemorrhage occurred when cerebral blood flow recovered after the hypoxic event.