Sex differences in learning and memory ability in hypoxic-ischemic brain injury in newborn mice
LIN Aijin;WANG Jieqiong;YI Shasha;AO Lijuan;CHEN Moxian;College of Rehabilitation, Kunming Medical University;
Objective To investigate the effect of sex on learning and memory ability of newborn mice with hypoxic-ischemic brain injury. Methods Fifty C57 BL/6 mice aged 10 days were divided into hypoxia-ischemia group and sham group according to the random number table method, and there were 28 in the hypoxic-ischemic group and 22 in the sham group with half female and half male respectively. In the ischemia-hypoxia group, the left common carotid artery was ligated and then the mice were placed in 34℃ hypoxia chambers with 8% oxygen and 92% nitrogen mixture for45 minutes. In the sham group, only the skin of the left neck was cut and sutured. After 2 months, Y maze test and Morris water maze test were used to evaluate the learning and memory ability of mice. Results The success rate of the hypoxicischemic group was 71.4%(20/28), and that of the sham group was 100.0%(22/22), a total of 42 mice were enrolled in the experiment. In Y maze test, there were differences in entries and total distance of new arms between the two groups(entries: F=16.068, P0.001; total distance: F=8.532, P=0.007); compared between different groups in the same gender, the entries and total distance of new arms in the hypoxic-ischemic group were lower than those in the sham group with statistically significant differences(entries in males: P=0.001, entries in females: P=0.012; total distance in males: P=0.010,total distance in females: P=0.046). Compared between males and females in the same group, the entries and total distance of new arms of females were higher than those of males in the hypoxic-ischemic group, with statistically significant differences(P=0.039, 0.043). In Morris water maze test, the escape latency of positioning navigation in the hypoxicischemic group was higher than that in the sham group, and males showed more obviously poor performance(P0.001);in the experiment of space exploration, differences were found in the duration of stay and the target quadrant entries between the two groups(duration of stay: F=8.297, P0.001; entries: F=4.042, P=0.014), and there were statistically significant differences in the same gender males and females in the hypoxic-ischemic group and the sham group(duration of stay in males: P=0.003, duration of stay in females: P=0.038; entries in males: P=0.006, entries in females: P=0.041).Compared between males and females in the same group, the duration of stay and the target quadrant entries of females were higher than those of males in the hypoxic-ischemic group, with statistically significant differences(duration of stay:P=0.018; entries: P=0.032). Conclusions The learning and memory ability of newborn mice may be slightly impaired after hypoxic ischemic brain injury. There is significant difference in the effect on learning and memory ability between different genders, and the effect on males is higher than that on females.