[Impact of hypoxic-ischemic injury on brain development in neonatal rats of different sexes].

Objective: To investigate the impact of hypoxic-ischemic brain injury (HIBI) on brain development in neonatal rats of different sexes. Methods: From January 1 to December 31, 2018, 60 7-day-old SD rats were randomly divided into HIBI-F group (20 rats), HIBI-M group (20 rats), and control group (20 rats, 10 females and 10 males). The animal model of HIBI was established with Rice-Vannucci method, with the rats' left common carotid artery double-ligated and severed. The rats were then placed in an incubator and exposed to a hypoxic gas mixture (8% O(2), 92% N(2)) for 90 minutes. No intervention was given to the control group. Two weeks after HIBI, the motor development was evaluated by footprint analysis, the residual brain volume was measured by brain magnetic resonance imaging (MRI), and the damage of synaptic ultra structure was analyzed by transmission electron microscope. One-way ANOVA or χ(2) test was used for inter-group statistical analysis, and paired sample t test was used to compare the bilateral step length and toe distance of rats in the same group. Results: The mortality rate of HIBI-F was significantly higher than that of HIBI-M (20%(4/20) vs. 10%(2/20), χ(2)=40.000, P=0.001). The right step length and toe distance in HIBI-M group and HIBI-F group were significantly shorter than those in control group ((7.5±0.3) cm and (7.9±0.5) cm vs. (8.2±0.5) cm, F=9.605, P<0.01, (0.9±0.1) cm and (1.0±0.0) cm vs. (1.1±0.1) cm, F=71.437, P<0.01). Besides, according to above data, the right step length and toe distance in HIBI-M group were significantly shorter than those in the HIBI-F group (both P<0.01). Furthermore, the right step length was significantly shorter than the left step length ((8.3±0.4) and (8.3±0.5) cm, t=5.289 and 10.580, P=0.001 and 0.010, respectively) and toe distance ((1.1±0.1) and (1.1±0.1) cm, t=7.953 and 6.435, respectively, both P<0.01) in both HIBI-M group and HIBI-F group. Similarly, the synaptic gap of the left precentral gyrus neurons was longer in HIBI-M group and HIBI-F group than that in control group ((23.4±1.3) and (19.7±1.6) nm vs. (18.9±0.6) nm, F=71.719, P<0.01), and also longer in HIBI-M group than that in HIBI-F group (t=7.645, P<0.01). Likewise, the residual brain volume in HIBI-M group and HIBI-F group was significantly less than that in control group ((67±4)% and (75±5)% vs. 100%, F=406.122, P<0.01), and the residual brain volume in HIBI-M group was significantly less than that in HIBI-F group (t=-5.281, P<0.01). Conclusions: Male neonatal rats are more vulnerable to HIBI and have severer subsequent brain injury and hemiplegia. Different treatment strategies for HIBI patients of different sexes should be developed.目的： 探讨不同性别缺氧缺血性脑损伤（HIBI）新生大鼠脑发育的差异。 方法： 2018年1月1日至12月31日，新生7日龄SD大鼠60只（雌性30只、雄性30只），按随机数字表法将大鼠分为HIBI组40只（雄性20只、雌性20只），对照组20只（雌性10只、雄性10只）。HIBI组大鼠采用Rice-Vannucci方法制作缺氧缺血性脑损伤模型，分离左侧颈总动脉，双重结扎后切断，再置于8%O(2)和92%N(2)的混合气体的缺氧箱中90 min；对照组不进行任何处理。缺氧缺血处理后2周，应用步迹分析评价各组大鼠21日龄运动发育功能，头颅磁共振成像（MRI）测量大鼠脑组织的残存脑容量，透射电镜下分析运动区域神经元突触结构的破坏程度。采用方差分析和χ(2)检验进行组间统计学比较，同组步长及趾间距比较采用配对t检验。 结果： HIBI-雄性组大鼠的病死率明显高于HIBI-雌性组[20%（4/20）比10%（2/20），χ(2)=40.000，P=0.001]；HIBI-雄性组和HIBI-雌性组大鼠脑损伤对侧（右侧）步长及趾间距均明显小于对照组[（7.5±0.3）和（7.9±0.5）比（8.2±0.5）cm，（0.9±0.1）和（1.0±0.0）比（1.1±0.1）cm，F=9.605、71.437，P均<0.01]；且HIBI-雄性组均明显小于雌性组（P均<0.01）。HIBI-雄性组和HIBI-雌性组大鼠右侧步长及趾间距均明显小于同组左侧步长[（8.3±0.4）和（8.3±0.5）cm，t=5.289、10.580，P=0.001、0.010]及趾间距[（1.1±0.1）和（1.1±0.1）cm，t=7.953、6.435，P均<0.01]。HIBI-雄性组与HIBI-雌性组的残存脑容量明显小于对照组[（67±4）%和（75±5）%比100%，F=406.122，P<0.01]，其中HIBI-雄性组小于HIBI-雌性组（t=-5.281，P<0.01）。HIBI-雄性组和HIBI-雌性组左侧中央前回神经元突触间隙均明显大于对照组[（23.4±1.3）和（19.7±1.6）比（18.9±0.6）nm，F=71.719，P<0.01]，其中HIBI-雄性组大于HIBI-雌性组（t=7.645，P<0.01）。 结论： 雄性新生大鼠更易受到HIBI的危害，具有更严重的脑损伤程度及偏瘫症状，对不同性别HIBI患儿应采用不同的更合适的治疗策略。.