消退训练对大鼠条件性恐惧行为及海马CA1区突触超微结构的影响

目的研究消退训练对大鼠条件性恐惧行为和海马CA1区突触超微结构的影响。方法成年雄性SD大鼠40只,简单随机抽样分为正常组(n=8)、消退对照组(n=16)和消退组(n=16)。在训练后不同时间(消退后7、21 d,恐惧建立后8、22 d)进行恐惧行为测试。采用透射电镜观察各组大鼠海马CA1区突触超微结构。结果①在消退后7 d和21 d,消退组的消退保持成绩显著高于消退对照组(P<0.05,P<0.01),而与正常组无显著差异(P>0.05)。②消退训练后7 d,消退组海马突触数密度显著高于消退对照组(P<0.05),与正常组之间无显著差异(P>0.05);消退训练后21 d,3组之间均无显著差异(P>0.05)。③消退训练后7 d和21 d,消退组海马突触间隙宽度显著低于正常组(P<0.05,P<0.01),并且在消退训练后21 d,消退组突触间隙宽度显著低于消退对照组(P<0.05)。④与正常组相比,消退训练后7 d和21 d,消退组PSD厚度均显著升高(P<0.01);且在消退训练后21 d,消退组PSD厚度显著高于消退对照组(P<0.05)。⑤各组之间活性区长度均无显著差异(P>0.05)。结论恐惧建立后24 h进行消退训练能够部分改变条件性恐惧引起的海马CA1区突触超微结构的变化,减轻条件性恐惧大鼠的僵立行为。

Effects of extinction training on conditioned fear behaviour and synaptic structure in hippocampal CA1 area in fear conditioned rats

Objective To determine the effect of fear extinction training on the behaviours and the ultrastructure of hippocampal CA1 area in fear conditioned rats.Methods Forty male adult SD rats were randomly divided into native group(n=8),extinction control group(n=16) and extinction group(n=16).In 24 h after fear condition was established by reference instruction in the later 2 groups,extinction training was carried out in the extinction group and extinction retention test was performed in 7 and 21 d after fear extinction.The test was performed in 8 and 22 d in extinction control group.The changes of synaptic structure in CA1 of hippocampus were observed at 7 and 21 d after fear extinction.Results Compared with the extinction control group,the scores of extinction retention was significantly increased(P<0.01) at 7 and 21 d after extinction in the extinction group.There was no significant difference between extinction group and native group at 7 and 21 d.At 7 d after extinction training,the synaptic density was significantly higher in extinction group than that in the extinction control group(P<0.05),and there was no difference among groups at 21 d.Compared with native group,the width of synaptic gap was significantly lower at 7 and 21 d after extinction training in extinction group(P<0.01,0.05).At 21 d,the width of synaptic gap was significantly lower in the extinction group than that in the control group(P<0.05).But there was no significant difference between the extinction control group and native group at 7 and 21 d after extinction.Compared with native group,at 7 and 21 d after extinction training,postsynaptic density(PSD) was significantly thicker in extinction group(P<0.01).And at 21 d,the density was significantly thicker in extinction group than that in the extinction control group(P<0.05).There was no significant difference among the groups in active zone length.Conclusion Fear extinction training changes synaptic structure caused by fear conditioning and decreases the fear behavior.