| Objective: By establishing HIBD models, giving them a specific Caspase-3 inhibitor, AC-DEVD-CHO, observing the histopathologic changes and Caspase-3 activity in rat brain tissue, The immediate and long-term effects of AC-DEVD-CHO, and its optimal therapeutic dosage were evaluated for searching out a new way in treatment of neonatal HIE. Methods: according to modified Levine method, HIBD model was established, and then carrying out the study designed as follows. (1) The activities of Caspase-3 at 1h, 12h, 24h, 48h after HI insult were measured in rats' brain tissue extracts by cleavage of Ac-DEVD-AMC, a fluorescent substrate. Active Caspase-3 protein levels were detected in rat-brain tissues at 24h, 48h after HI insult with immunohistochemical method. The number of apoptotic cells in rat brains at 1h, 12h, 24h, 48h, 1W after HI insult were detected with terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling (TUNEL) method. (2) Activities of Caspase-3 in brain-tissues were measured at 24h after HI insult to neonatal rats, which were divided into several groups and treated with AC-DEVD-CHO ICV. in different dosage respectively. (3) The effects of AC-DEVD-CHO were observed by means of counting TUNEL-positive cells and Shuttle box trial, tiredness and activity trials when rats were reared to 1m old. Results:(1) Activity of Caspase-3 in the hemisphere ipsilateral to carotid artery ligation has significantly increased at 1h after HI insult and peaked at 24h before returning to near baseline level at 48 h. (2) The active caspase-3 positive cells detected by immunohistochemical method were significantly increased after HI. The percentage of positive cells in normal brain tissue was 0.65±0.67％. In the hemisphere ipsilateral brain tissue at 24h and 48h after HI insult were 52.9±7.9% and 41.5±5.7％. (3) The number of TUNEL-positive cells increased in a time-dependent manner in the hemisphere ipsilateral after HIBD. The percentages of TUNEL-positive cell in normal brain, 1h, 12h, 24h, 48h,1W after HI insult were 0.6±0.77 ％,5.2±1.93 ％,18.5±6.23 ％,44.13±8.41 ％,30.8±9.58 ％,14.0±7.1 ％. (4) The activity of Caspase-3 at 24h after HI insultdeclined corresponsively with the increasing dose of Ac-DEVD-CHO.ICV. (5) The percentage of TUNEL-positive cell in HIBD rats' brain-tissue administrated with Ac-DEVD-CHO.ICV. significantly decreased when compared with those administrated with N.S.ICV. (30.2±11.2% vs 44.6±12.4%,P<0.01). (6) The stimulating time of Ac-DEVD-CHO.ICV group in shuttle box trial is significantly less than control N.S.ICV. group (p<0.05). However,there is no significantly difference between the Ac-DEVD-CHO ICV. group and N.S. ICV. group in stimulation counts of shuttle box trail and in motor ability trials. Conclusions: 1. Caspase-3 in the hemisphere ipsilateral to carotid artery ligation of HIBD neonatal rats was significantly activated. 2. The counts of apoptotic cells increased in a time-dependent manner in hemisphere ipsilateral to carotid artery ligation after HIBD before declining. 3. Ac-DEVD-CHO.ICV. is helpful to decrease apoptotic neuronal death in HIBD rats. 4. Ac-DEVD-CHO.ICV. can improve the learning and memory abilities of HIBD neonatal rats. However, it's no use for improving the motor ability of the animals.
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