手术对异氟醚麻醉下老龄大鼠术后认知功能的影响

目的 探讨手术对老龄大鼠异氟醚麻醉下术后认知功能的影响.方法 健康雄性老龄SD大鼠72只,年龄20月,体重500～600 g,随机分为3组(n=24):对照组(C组)、异氟醚麻醉组(I组)和手术组(O组).C组吸入30%氧气2 h,I组吸入1.5%异氟醚和30%氧气的混合气体2 h,O组吸入1.5%异氟醚和30%氧气的混合气体2 h,并实施腹部手术.于麻醉结束后或术后24 h时随机取8只大鼠,取海马组织,采用免疫组织化学法和RT-PCR法分别测定神经元胆碱乙酰转移酶(ChAT)及ChAT mRNA的表达水平,其余大鼠进行Morris水迷宫实验,测定认知功能.结果 与C组比较,I组和O组逃避潜伏期延长,原平台象限停留时间缩短,穿越原平台次数减少,海马神经元ChAT mRNA及其蛋白表达水平降低(P<0.05);与I组比较,O组术后第4、5天逃避潜伏期延长,原平台象限停留时间缩短,海马神经元ChAT mRNA及其蛋白表达水平降低(P<0.05);与麻醉结束后或术后第3天比较,C组第4、5天逃避潜伏期差异无统计学意义(P>0.05),I组和O组逃避潜伏期延长(P<0.05);I组和O组麻醉结束后或术后第4、5天逃避潜伏期差异无统计学意义(P>0.05).结论 手术操作可加重异氟醚引起的老龄大鼠术后认知功能障碍,其机制可能与海马胆碱能神经元受损有关.

Effects of surgical operation on cognitive function in aged rats after isoflurane anesthesia

Objective To investigate the effects of surgical operation on the cognitive function in aged rats after isoflurane anesthesia. Methods Seventy-two aged male SD rats (20 months) weighing 500-600 g were randomly divided into 3 groups (n = 24 each): group C inhaled 30% O_2 for 2 h (control); group I was anesthetized with 1.5% isoflurane in 30% O_2 for 2 h (anesthesia) and group O underwent abdominal operation under 1.5% isoflurane (in 30% O_2) for 2 h (operation). Arterial blood samples were obtained at 0.5, 1 and 2 h of operation for blood gas analysis. Eight animals were killed at 24 h after anesthesia in each group. Their brains were immediately removed for detection of the expression of gene and protein of choline acetyltransferase (CHAT) in hippocampas by RT-PCR and immuno-histochemistry. Cognitive function were assessed by Morris water maze test the day before experiment, and once a day for 6 consecutive days starting from the 1 st postoperative day. Results The ChAT gene and protein expression in hippocampus was significantly decreased, and the the escape latency was significantly prolonged, and the frequency of crossing the original platform and the time of staying at the original platform quadrant were decreased in group 1 and O compaired with group C. Cognitive function became stable at day 4 in group B and C but at day 3 in group A. The ChAT gene and protein expression was significantly lower, and the escape latency was longer and the time of staying at the original platform quadrant was significantly shorter after anesthesia in group O than in group I. Conclusion Surgical operation can aggravate the cognitive dysfunction induced by isoflurane and the mechanism may be related to the injury of cholinergic neurons in hippoeampus.