雷帕霉素对婴儿期遗忘作用的研究

Effect of rapamycin on infantile amnesia

目的验证婴儿期遗忘现象并研究雷帕霉素对17日龄（P17）大鼠被动回避反应训练的记忆保留及海马新生神经元增殖的影响。方法（1）P17和60日龄（P60）SD雄性大鼠。备42只，按随机数字表法分为电击组和非电击组．各组分别进行被动回避反应训练（非电击组在训练时不予电击），测试所有大鼠训练后0d、2d和7d的记忆保留；（2）84只P17SD雄性大鼠按随机数字表法分为溶媒组、雷帕霉素20mg／kg和40mg／kg组f每组又分电击组和非电击组2个亚组1，各组分别在被动回避反应训练后腹腔注射溶媒或雷帕霉素，测试所有大鼠训练后2a（P19）和7d（P24）的记忆保留；（3）48只P17SD雄性大鼠按随机数字表法分为正常组、溶媒组、雷帕霉素20mg／kg和40mg／kg组，利用BrdU标记海马齿状回细胞增殖，行BrdU／DCX免疫荧光染色观察雷帕霉素用药后2a（P19）和7d（P24）海马新生神经元的增殖情况。结果（1）电击训练后0dP17和P60大鼠被动回避反应测试的反应潜时比较差异无统计学意义（P〉0．051，训练后2d和7d2组比较差异均有统计学意义（P〈0．05），P17大鼠有更快的遗忘速度而P60大鼠能保持稳定的记忆水平。非电击训练各组各时间点反应潜时比较差异无统计学意义（P〈0．05）。（2）溶媒组与雷帕霉素20mg／kg和40mg／kg组电击训练后2d反应潜时比较差异无统计学意义（P〉0．051，训练后7d雷帕霉素20mg／kg、40mg／kg组与溶媒组反应潜时比较差异均有统计学意义（P〈0．051，雷帕霉素能增加P17大鼠的记忆保留。非电击训练各组各时间点反应潜时比较差异无统计学意义（p〈O．05）。（3）溶媒组在P19、P24双侧海马齿状回BrdU、BrdU／DCX阳性细胞计数与雷帕霉素20mg／kg、40mg／kg组比较差异均有统计学意义（P〈0．05），雷帕霉素能减少海马齿状回新生神经元的增殖。结论婴儿期遗忘现象存在，且雷帕霉素可能通过减少海马齿状回神经发生增加P17大鼠的记忆保留，减缓婴儿期遗忘。

Objective To verify the infantile amnesia phenomenon and discuss the effect of rapamycin injection on infantile amnesia and hippocampal neurogenesis. Methods （1） In experiment one, 17-day-old （P17） and 60-day-old （P60） male Sprague-Dawley rats （n=84） were trained in a passive-avoidance task （they were randomly sub-divided into the shocked group and non-shocked group）; all rats were tested immediately, 2 and 7 days after training for memory retention. （2） In experiment two, P17 rats （n=84） were randomly divided into three groups： vehicle group, 20 mg/kg rapamycin group and 40 mg/kg rapamycin group （they were sub-divided into the shocked group and non-shocked group）; P17 rats were immediately injected with either vehicle or rapamycin after passive-avoidance training, and memory retention was evaluated 2 and 7 days after training. （3） In experiment three, P17 rats （n=48） were randomly divided into four groups： normal group, vehicle group, 20 mg/kg rapamycin group and 40 mg/kg rapamycin group; immunofluorescence staining of BrdU/DCX was detected to observe the hippocampal neurogenesis at post-natal day 19 （P19） and post-natal day 24 （P24） after vehicle or rapamycin injection at P17 rats. Results In experiment one, P17 and P60 shocked rats exhibited comparable levels of crossing latencies when being tested immediately （P〉0.05）, when being tested after 2 days and 7 days, P17 rats forgot more rapidly than P60 rats （P〈0.05）; there were no age-related