摘要目的 探讨不同消退训练方式对成年大鼠恐惧记忆、DNA甲基化蛋白及海马新生神经元的影响.方法 雄性SD大鼠随机分成4组:正常对照组、消退对照组、传统消退组和提取消退组.大鼠给予“声音-电击”刺激建立条件性恐惧记忆模型,再进行传统消退或提取消退训练,在第1天、第4天和第7天检测不僵直时间百分比(即消退保持成绩),利用免疫印迹、免疫组织化学检测海马DNA甲基化蛋白表达和新生神经元情况.结果 消退训练后第4天,不僵直时间百分比传统消退组[(28.06±11.33)％]和提取消退组[(30.28±11.48)％]高于消退对照组[(21.35±9.45)％],但低于正常对照组[(75.65±8.69)％](t=2.204,2.517,7.955,7.023,P＜0.05).消退训练后第7天,不僵直时间百分比提取消退组[(69.72±13.62)％]高于消退对照组[(24.27±11.67)％,t=7.052,P＜0.01]和传统消退组[(50.64±12.51)％,t=2.451,P＜0.05],但与正常对照组[(72.03±9.36)％]差异无统计学意义(t=0.251,P＞0.05).消退训练后第4天,传统消退组和提取消退组大鼠海马Dnmt-1、MBD-2表达低于消退对照组,但高于正常对照组(P＜0.05).消退训练后第7天,提取消退组的海马Dnmt-1、MBD-2表达明显低于消退对照组和传统消退组(P＜0.05),但与正常对照组差异无统计学意义.消退训练后第4天,传统消退组和提取消退组大鼠海马Brdu阳性细胞表达高于消退对照组,但低于正常对照组(P＜0.05).消退训练后第7天,提取消退组的海马Brdu阳性细胞表达明显高于消退对照组和传统消退组(P＜0.05),但与正常对照组差异无统计学意义.结论 消退训练可以降低大鼠的条件性恐惧记忆,并且提取消退范式优于传统消退范式,该作用可能是通过降低海马DNA甲基化和增加新生神经元来实现.

abstractsObjective To investigate the effect of different extinction training on fear memory,DNA methylation protein and hippocampal newborn neurons in adult rats.Methods Male SD rats were randomly divided into four groups:naive group,conditioned fear group,traditional-extinction group and retrieval-extinction group.Conditioned fear models were established by tone paired foot shock,and retrieval-extinction training or traditional-extinction training were performed in adult rats.Retention test,Western blot and immunnohischemistry were used to detect the no-freezing time percentage,the DNA methylation protein level,the newborn neurons respectively at 1d,4d and 7d after different extinction training.Results The traditional-extinction group((28.06± 11.33) ％) or retrieval-extinction group((30.28± 11.48) ％) had higher percentage of no-freezing time than that of conditioned fear group((21.35±9.45) ％),and lower percentage of no-freezing time than that of naive group ((75.65±8.69)％) (t=2.204,2.517,7.955,7.023,all P＜0.05) at the fourth day after extinction training.At the seventh day after extinotion training,the retrieval-extinction group ((69.72±13.62)％) had higher percentage of no-freezing time than traditional-extinction group((24.27± 11.67)％,t=7.052,P＜0.01) or conditioned fear group((50.64± 12.51)％,t=2.451,P＜0.05),and showed no significant difference compared with naive group((72.03±9.36) ％,t=0.251,P＞0.05).The expressions of Dnmt-1 and MBD-2 in traditional-extinction group or retrieval-extinction group were lower than those in conditioned fear group,and higher than those in naive group (P＜0.05) at 4 d after extinction.training.At 7 d after extinction training,the expressions of Dnmt-1 and MBD-2 in retrieval-extinction group were lower than those in traditional-extinction group or conditioned fear group (P＜0.05),and there was no significant difference between retrieval-extinction group and naive group.The Brdu-positive cells of traditional-extinction group or retrieval-extinction training were higher than conditioned fear group,and less than naive group (P＜0.05) at the fourth day after extinction training.At the seventh day after extinction training,the Brdu-positive cells in retrieval-extinction group were higher than those in traditional-extinction group or conditioned fear group (P＜0.05),and there was no significant difference between retrieval-extinction group and naive group.Conclusion The extinction training can decrease fear memory of rats with conditioned fear memory,and the effect of retrieval-extinction training were better than traditional-extinction training,which may be associated with the increases of hippocampus newborn neurons and the decline of DNA methylation.