Objective To investigate the pathological changes in neonatal rats after hypoxic-ischemic insults. Methods 70 normal 7-day-old Wistar rats were divided into two groups randomly: hypoxic-ischemic and control group. The left carotid arteries were permanently ligated and cut in hypoxic-ischemic group. All the animals were exposed hypoxia (92% N2, 8% O2) for 2 h in a constant thermal environment. All the brain tissues were observed with electronmicroscopy, HE and immunohistochemistry stain 7 d, 14 d and 30 d after injury. Results HE stain showed that neurocytes arranged disorder in the side of the carotid ligation 7 d after injury. Some degenerated neurocytes, swelled cells and inflammatory cell infiltration also visualized. Many capsular spaces were observed in the side of the carotid ligation 30 d after injury. Immunohistochemistry staining showed Myelin basic protein (MBP) positive neurocytes gradually decreased, and glia fibrillary acidic protein (GFAP) positive neurocytes gradually inreased in the periventricular zone with the time lapsed. It was observed that the neurocytes were edema, many mitochondrias were vacuolus, caryotins were condensed under transmission electron microscope 7 d after operation. The morphocytology of the neurocytes were irregulated obviously, part of nuclear membranes were broken down with the content leakaged 30 d after operation. Conclusion The characteristics of periventricular leukomalacia can be developed after hypoxic-ischemic insults in the rats.

Objective To establish a new rat model of perinatal brain damage. Methods Wistar rats were randomized into 3 groups: lipopolysaccharide （LPS） plus hypoxia (H) group: 17 d pregnant rats exposure in utero to LPS followed by hypoxia; hypoxia (H)/ ischemia (I) group: postnatal day 7 (P7) pups ligated the right common carotid artery followed by exposure to hypoxia (8% O2 ) for 2 h; control group: P7 pups incised the anteriorl cervical skin only. The footprint analysis, compound muscle action potential (CMAP) and pathological observation were performed after 4 weeks. Results The left limb footprint repeatability of rat in HI and LPS plus H groups was poorer than that in control group （P<0.05）. The hindlimb quadriceps CMAP of rats in HI and LPS plus H groups showed that the wave amplitude was lower than that in control group （P<0.05）. The periventricular cells were irregular, and the periventricular leukomalacia was seen. The morphous of the neurocytes was irregular obviously, part of the nuclear membranes was broken down with the content leakage under transmission electron microscope. Conclusion The animal model for cerebral palsy has established, that mimics more the occurrence of this disease in human.