RESUMO
Objective:To assess the severity of hypoxic-ischemic brain damage (HIBD) in neonatal rats and predict the occurrence of subsequent neurobehavioral abnormalities after brain injury by scoring and magnetic resonance imaging (MRI).Methods:7-day-old of 60 Sprague-Dawley (SD) rats were randomly divided into control group (14 rats), sham operation group (14 rats) and HIBD model group (32 rats). HIBD model was established by right common carotid artery dissection with Rice-Vannucci method and hypoxia. Within 24 h after modeling, the rats in the model group were evaluated by general condition score and Longa score, and the surviving rats with moderate and severe HIBD were selected for the experiment. 24 h after modeling, 5 rats of the model group were randomly selected for 2,3,5-triphenyltetrazole chloride staining to verify cerebral infarction. 1 week after modeling, 6 rats from each group were randomly selected for hematoxylin-eosin staining to observe HIBD brain injury. 4 weeks after modeling, 4 rats were randomly selected from the control group and the sham operation group, and 8 rats from the remaining model group were used to evaluate the volume of brain damage by MRI. 5-6 weeks after modeling, the remaining 8 rats from each group were subjected to the Cylinder test, and at 13 weeks, they underwent the Morris water maze test to evaluate their neurobehavior.Results:In HIBD model group, 19 rats with moderate to severe HIBD were selected from 32 rats. 24 h after modeling, cerebral infarction was verified in all rats, indicating moderate to severe HIBD. Brain tissue pathology observed 1 week after modeling revealed predominantly gray matter brain damage. MRI showed that 7 out of 8 rats had moderate to severe HIBD. Compared to the control and sham operation groups, the model group exhibited a significant decrease in the usage rate of the left forelimb in the Cylinder test at 5-6 weeks after modeling ( P<0.05), and the latency period in Morris water maze test was significantly prolonged at 13 weeks after modeling ( P<0.05), and the times of crossing platform quadrant were significantly reduced ( P<0.05). There was no significant difference in the right brain injury volume between 24 h and 4 weeks model group ( P>0.05). The brain injury volume in model group was negatively correlated with the usage rate of left forelimb in cylinder test at 5-6 weeks and the times of crossing platform quadrant in Morris water maze test at 13 weeks ( P<0.05), and positively correlated with latency period in Morris water maze test at 13 weeks ( P<0.05). Conclusions:Within 24 h of HIBD modeling, the severity of brain injury can be preliminarily predicted by general condition score and Longa score. 4 weeks after modeling, in the chronic phase of brain injury, MRI was proved to be an excellent predictor for mid-term and long-term neurobehavioral abnormalities in HIBD rats.