| Hypoxic-ischemic brain damage (HIBD) often leads to the death of neonates or severe neurological sequelae. But the mechanism of HIBD has not yet been recognized and there are not efficacious means of prevention and treatment. With the advance of study about HIBD,there is increasing evidence that neuronal nitric oxide synthase (nNOS) mediates early neuronal injury . In our experiment HIBD model was established, 7-nitroindazole (7-NI) was injected intraperitoneally 30 min before hypoxia. NOS, NO, SOD and MDA were measured , neuronal apoptosis was examined by TUNEL method,then we study the protective effect of 7-NI on neonatal rat models with HIBD. MethodsNeonatal 7-day-old Wistar rats were under a middle anterior neck incision. The left common carotid artery was isolated and ligated,then the pups were exposed to hypoxic environment (8%O2) for 2 hours.Eighty-four animals were randomly assigned to the sham-operation group, HIBD or 7-NI treated group. Twelve were used to histological study of the sham-operation and HIBD group by henmatoxylin-eosin (HE) . Fifty-four rats were used to examined NOS, NO, SOD and MDA.Animals were killed at Ih (during hypoxia, HH,), 2h (end of hypoxia, H2h), 6h (4h after the end of hypoxia, H6h) and 8h (6h after the end of hypoxia , Hgh) after the start of hypoxia. Eighteen rats were killed at 24h after HIBD and used to examined neuronal apoptosis by TUNEL method.Results1. Histological study(1) Sham-operation group: There was no obvious sign of neuronal damage and with cells of apparently normal appearance in the brain tissue.(2) H1h: There was no different histological appearance compared to the sham-operation group.(3) Han: Degenerated neurons were scattered in the cortex and hippocampus, defined as those with mildly shrunken somata, eosinophilic cytoplasm and intensely staining nuclei.(4) H6h and Hgi,: Laminal and patchy distribution of neuronal necrosis and edema were apparent in the cortex and hippocampus. Morphological alterations were cellular shrinkage, cytoplasmic homogeneous eosinophilia, nuclear pyknosis and widened pericellular spaces.(5) 24h after HIBD: Neuronal necrosis is severer. Pyramidal cells showed disorders in the hippocampus and proliferation of glial cells appeared.2. The results of NOS, NO, SOD and MDA examination(1) Comparison between the HIBD and sham-operation group:Compared to the sham-operation group, NOS and NO both increased significantly (P<0.01) , SOD droped but MDA increased in each time point (P<0.05) .(2) HIBD group: NOS, NO were significantly different in the time points of HIBD group(NOS: F=24.357,P<0.05; NO: F=14.293, P<0.05). The levels of NOS and NO in H1h were higher than H2h, H6h and H8h were higher than HIH and H2h , H8h were higher than HSH. SOD and MDA were different significantly in each time point (SOD: F=18.809, PO.05; MDA: F=41.562, P<0.05) . SOD gradually decreased but MDA improved.(3) Comparison between the 7-NI treated and HIBD group: NOS and NO were both lower in 7-NI treated group than HIBDgroup (P<0.05) . SOD increasedand MDA decreased (P<0.05 )(4) Comparison between the 7-NI treated and sham-operation group: NOS, NO, SOD and MDA showed no differences significantly in Hih(P>0.05). But there were significant differences in H2h , H$h and Hgh (P<0.05) .3. Neuronal apoptosisThere were no apoptosis neurons in the sham-operation group, but neuronal apoptosis increased significantly in the cortex and hippocampus in the HIBD group. Neuronal apoptosis decreased significantly in the 7-NI treated group than in the HIBD group(P<0.001).Conclusions1. We induced HIBD in neonatal seven-day-old Wistar rats that consisted of unilateral carotid ligation followed by exposure to a hypoxic environment(8%O2) for 2 hours. Histopathologic examination of the ligated side of cerebral cortex and hippocampus showed edema and neuronal degeneration and necrosis. This confirmed that the establishment of neonatal rats model of HIBD was successful.2. 7-NI inhibited activity of nNOS,... |
