Homer 1a RNA干扰后大鼠脑组织突触超微结构变化

Changes of Ultrastructure of Synapses in Brain Tissue of Rats after RNA Interference of Homer 1a

目的观察Homer 1a RNA干扰(RNAi)后SD大鼠脑组织突触数目及突触超微结构的变化,探讨其变化在注意缺陷多动障碍(ADHD)发病机制中的作用。方法将24只SD大鼠随机分为2组:Homer 1a RNAi组(RNAi组,n=12)和对照组(n=12)。运用侧脑室注射技术,分别向2组大鼠的侧脑室注射针对Homer 1a的RNA干扰病毒和无义病毒,等待病毒起效时间为7 d,7 d后从每组大鼠中随机抽取3只,应用8 g·L-1多聚甲醛灌注固定脑组织,利用电镜技术观察大鼠纹状体及前额叶皮质突触超微结构的变化。结果电镜结果显示,RNAi组与对照组相比,纹状体突触间隙显著减小(t=2.85,P=0.01);突触活性区长度有增大趋势,但差异无统计学意义(t=1.80,P=0.08);突触数目(t=0.59,P=0.57)及突触后致密物厚度(t=0.30,P=0.77)无明显差异。RNAi组前额叶皮质较对照组突触活性区长度显著增大(t=2.40,P=0.02);突触后致密物厚度(t=1.72,P=0.09)有增大趋势,但差异无统计学意义;突触数目(t=0.13,P=0.89)及突触间隙(t=0.25,P=0.81)无明显差异。结论 Homer 1a RNAi大鼠在表现类似ADHD行为的同时,脑组织突触超微结构发生改变,提示Homer 1a参与的突触超微结构改变可能与ADHD的病因和发病机制相关。

Objective To observe the changes of ultrastructure and number of synapses in brain tissue of Sprague Dawley （SD） rats af- ter Homer 1 a RNA interference （ RNAi）, and to investigate the roles of changes of ultrastructure and number of synapses in the etiology and pathogenesis of attention deficit hyperactivity disorder （ADHD）. Methods Twenty - four SD rats were randomly divided into the Homer la RNAi group （RNAi group,n = 12）and the control group （n = 12）, and they were injected with Homer 1 a RNAi lentivirus or nonsense lentivirus by using intracerebroventricular injection technology, respectively. After 7 days of intracerebroventricular injection ,3 rats were taken from each group randomly, brain tissue was perfused and fixed with paraformaldehyde, then the ultrastructure and number of synapses in corpus striatum and prefrontal cortex were observed using electron microscopy. Results Synaptic clefts width in the corpus striatum in the Homer 1 a RNAi group were dramatically reduced compared with that in the control group （ t = 2.85, P = 0.01 ） ; the synaptic active zone length was increased in Homer 1 a RNAi group, however, this change was not statistically significant （ t = 1.80, P = 0.08 ）. There were no significant differences in synapse number （ t = 0.59,P = 0.57 ） and postsynaptic density （ t = 0.30, P = 0.77 ） between the 2 groups. Synaptic active zone length of pre- frontal cortex in the Homer 1 a RNAi group was significantly augmented compared with that in the control group （t = 2.40,P = 0.02 ）, and the thickness of postsynaptic density slightly increased, but the difference was not statistically significant （ t = 1.72, P = 0.09 ）, as neither the num- ber of synapse（t =0.13 ,P =0.89） nor synaptic clefts （ t = 0.25 ,P = 0.81 ） had significant difference between control group and Homer la RNAi group. Conclusions After Homer 1 a RNAi,rats＇ performance is similar to the ADHD behavior accompanied with ultrastructure change of synapse both in corpus striatum and prefrontal cortex. It can implicate that ultrastructure change of synapse may be involved in the etiology and pathogenesis of ADHD.