| The Effects of Unilateral Brain Hypoxia-ischemia on the Contralateral Cerebral Hemisphere in the Neonatal Rat. |
| Sang Kook Lee, Seung Won Park, Young Baeg Kim, Eun Sup Park, Byung Kook Min, Sung Nam Hwang, Duck Young Choi, Jong Sik Suk |
1Department of Neurosurgery, College of Medicine, Chung-Ang University, Seoul, Korea.
2Department of Pathology, College of Medicine, Chung-Ang University, Seoul, Korea. |
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| ABSTRACT |
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Injury to specific areas of the immature brain, in both the human and animals, can result in compensatory reorganization in undamaged adjacent or contralateral areas. The functional plasticity of such compensatory hypertrophy is not well known, but in some cases may be responsible for recovery of function. In order to investigate the effect of unilateral ischemic injury on the contralateral cerebral hemisphere in neonatal rats, early and late changes in various areas of both cerebral hemispheres were assessed. Seventy-seven seven-day-old Sprague-Dawley rats underwent unilateral carotid artery ligation and were then exposed to hypoxia(8% oxygen) for 3 hours. The animals were killed one week(Group I, 58 rats) and three months(Group II, 19 rats) later.
Twelve rats, comprising Group III, were exposed to hypoxia for 3 hours without carotid artery ligation. The control group, consisting of 19 rats, did not undergo any of the above procedures. In each slice of brain tissue(4mm posterior to the bregma), the area of the whole brain, each hemisphere, and the frontoparietal, temporal and hippocampal regions in each hemisphere were measured, using the image analysis program(Optimas 5.2), and to assess which regions were affected, proportions of each hemisphere occupied by each region were compared. In Group II, the proportional areas of the frontoparietal(p<0.05) and temporal(p<0.01) regions in the contralateral hemisphere increased significantly, compared with the control group, but the hippocampal region showed no significant change. In Group I, there was no contralateral hypertrophy. The ipsilateral hemisphere showed significant atrophy and there was weight reduction in Groups I(p<0.001) and II(p<0.001). This study suggests that unilateral hypoxia-ischemia results in ipsilateral hemispheric atrophy and contralateral hypertrophy, especially in the frontoparietal and temporal areas, may contribute to some functional recovery and compensation in addition to uncrossed corticospinal or other descending motor systems. |
| Key Words:
Immature brain; Hypoxia-ischemia; Hypertrophy; Functional recovery; Compensation |
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