幼龄大鼠深低温低流量脑损伤模型的建立和评估

Establishment and evaluation of the model of deep hypothermic low flow in young rats

目的建矿幼龄大鼠深低温低流量（deep hypothennia low flow，DHLF）脑损伤模型，研究DHLF期间大鼠脑血流龟的变化及脑损伤程度。方法3周龄健康sD大鼠12只，雌雄不限，体重45～50g，按随机数字表法分为假手术组和模型组。建立DHLF模型后，利用激光多普勒血流监测仪于DHLF期间连续监测腑血流量变化，并在降温前、降温至（21．0±0．5）℃、DHLF0～5min、DHLF25～30min、DHLF55～60min、DHLF115～120min和DHLF术后0～5min这7个时间段记录局部脑血流量（rI=BF）变化，降温前rCBF作为基线水平。另取3周龄健康SD大鼠60只，按随机数字表法分为假手术组和模型组，每组设5个时相点：DHLF术后1h、6h、24h、72h和7d，每个时相点6只，采用HE染色和TUNEL法分别观察不同时相点脑组织病理改变及细胞凋亡变化，并于术后24h、72h和7d进行神经功能缺陷评分（NDS）。结果假手术组和模型组在降温至（21．0±0．5）oC时rCBF分别降至基线水平的（41．1±4．2）％和（40．7±3．4）％，且模型组rCBF在DHLF0～5min内进一步降低至（15．7±3．5）％（P〈0．01），而在DHLF期间无明显改变。与假手术组比较，模型组在术后24h和72h时NDS评分显著降低（P〈0．05或0．01），且脑组织病理改变明显，TUNEL阳性细胞在术后6h、24h、72h和7d均显著增高（P〈0．01）。结论DHLF模型可以造成脑损伤，与细胞凋亡有关，且操作简单，是一种较为理想、可靠的DHLF脑损伤模型，可近似于临床心脏直视手术DHLF过程。

Objective To investigate the changes of cerebral blood flow and the level of brain injury in a rat model of deep hypothermia low flow （DHLF）. Methods Twelve SD rats aged 3 weeks were randomly divided into sham group and model group. Regional cerebral blood flow （rCBF） of all rats was measured continuously during the operation by laser Doppler flowmetry, and the changes of rCBF were measured before temperature decreased, when the temperature decreased to （21.0 ± 0.5 ）℃ , 0-5 minutes, 25-30 minutes, 55-60 minutes, 115-120 minutes during DHLF and 0-5 minutes after DHLF operation. Another 60 SD rats aged 3 weeks were randomly divided into sham group and model group. Six rats of each group were sacrificed at 1, 6, 24, 72 hours and 7 days after DHLF operation to detect the pathological changes of the brain and the neuronal apoptosis by HE staining and TUNEL assay. The neurological deficit score （NDS） was recorded at 24, 72 hours and 7 days after operation for evaluating the neurologic functional outcome. Results When the temperature was decreased to （21.0 ± 0.5） ℃, the levels of rCBF of sham group and model group were significantly decreased to （41.1 ± 4.2）% and （40.7 ± 3.4）% of the baseline value, and the rCBF level of model group was further decreased to （ 15.7 ± 3.5 ）% of the baseline value 0-15 minutes during DHLF （P 〈0.01 ） , with no obvious changes in all the time intervals during DHLF. Compared with the sham group, the scores of NDS of model group were significant lower at 24 and 72 hours after operation （P 〈0.05 or 0. 01 ）. Besides, a significant pathological change of the brain tissue and a increased percentage of TUNEL-positive staining cells were observed in model group at 6, 24, 72 hours and 7 days after operation （P 〈 0.01 ）. Conclusions Rat model of DHLF is an ideal and reliable model of brain injury, for it is similar to DHLF procedure of clinical cardiac operation.