氯胺酮对老年大鼠空间学习记忆功能和海马胆碱乙酰转移酶的影响

目的:观察临床剂量的氯胺酮麻醉对老年大鼠1周和3周时空间学习记忆功能和海马胆碱乙酰转移酶(ChAT)的影响。方法:♂老年SD大鼠48只,随机分为4组(n=12)。对照1周组(C1)、氯胺酮1周组(K1)、对照3周组(C3)、氯胺酮3周组(K3)。K1、K3组腹腔首次注射氯胺酮80mg/kg,随后每隔15min追加1/2首剂量,共追加3次;C1、C3组腹腔注射等量生理盐水。处理后第1周,C1、K1组大鼠进行Morris水迷宫试验,测试各组大鼠寻找隐匿台的逃避潜伏期和空间搜索能力,每日4次,连续6d;处理后第3周,C3、K3组大鼠进行同样的测试。水迷宫测试结束后,将大鼠麻醉后灌注取脑,分别应用HE染色观察组织细胞及免疫组化方法检测ChAT阳性细胞数的改变。结果:①水迷宫结果,K1组第1~4d,大鼠寻找隐匿台的潜伏期明显长于C1组(P<0.05或0.01),但第5、6d时,二者之间无明显区别(P>0.05);对隐匿台空间位置的记忆能力K1组低于C1组(P<0.05)。K3组与C3组之间水迷宫结果比较,无明显统计学意义(P>0.05)。②免疫组化结果,K1组大鼠海马部位ChAT阳性细胞数小于C1组,差异有统计学意义(P<0.05);但K3组与C3组相比,差异无统计学意义(P>0.05)。③HE染色结果:电镜下各组大鼠海马神经元结构未见明显异常。结论:临床相关剂量的氯胺酮麻醉可导致老年大鼠短期空间学习记忆功能障碍,随时间推移,功能渐恢复,其机制可能与中枢胆碱能系统功能损害有关。

Effects of ketamine on spatial learning and memory behaviour and expression of ChAT in hippocampus of aged rats

Objective:To study the effects of administering anesthetic ketamine on the spatial learning and memory behavior and the expression of ChAT in hippocampus of aged rats. Methods: 48 aged male SD rats were randomly divided into 4 groups(n=12): 1 week control group(C1), 1 week ketamine group(K1), 3 week control group(C3), 3 week ketamine group(K3). Ketamine groups(K1 and K3) received the anesthetic with an initial dose of 80 mg/kg by intraperitoneal injection. Half of the initial dose were administered in every other 15min with 3 times in all. The control groups(C1 and C3)were given equal volume of 0.9% saline intraperitoneally. After testing the ability of learning and spatial localization for C1 and K1 groups by Morris water maze(MWM), the rats were anesthetized for removing the hippocampus while being infused. HE staining and immunocytochemistry were used to examine hippocampus neurons and ChAT positive cells. Results: ①MWM: At day 1 to day 4, the escape latency in K1 group was observed significantly longer compared with C1 group(P<0.05 or P<0.01), but at day 5 and 6, there was no difference(P>0.05), and the time consumption across the original platform in the spatial probe test in K1 group was less than C1 group (P<0.05). ②Immunocytochemistry: In K1 group, ChAT positive cells was less than that of C1 group(P<0.05), but there was no significantly difference between group K3 and group C3 (P>0.05).③HE assay: Electronic microscopy showed no abnormal changes of hippocampal neurons in two groups. Conclusion: When ketamine is administered in aged rats to the clinical dosage, it can affect the spatial learning and memory behavior. The impairment may be reversed with advance of time, which suggests that the mechanism of this damage might be related to the change of ChAT positive cells.