中文摘要：

目的观察边缘型维生素A缺乏幼鼠早期维生素A（VA）干预后，其学习记忆的恢复情况，并对其机制进行初步探讨。方法实验分为正常对照组、边缘型维生素A缺乏组（MVAD组）、胚胎干预组（VAI1组）和新生干预组（VAI2组）。正常对照组（幼鼠10只）母鼠和幼鼠均给予VA充足饲料；MVAD组（幼鼠19只）母鼠和幼鼠均给予边缘型维生素A缺乏饲料；VAI1组（幼鼠10只）母鼠给予边缘型维生素A缺乏饲料至孕14d，后改饲VA充足饲料，幼鼠饲VA充足饲料。VA12组（幼鼠13只）母鼠给予边缘型维生素A缺乏饲料至分娩，后改饲VA充足饲料，幼鼠饲VA充足饲料。待各组幼鼠长至7周龄，用穿梭箱主动回避反应实验测试学习记忆功能，离体脑片检测海马长时程增强（LTP），半定量RT-PCR技术检测RAR-α、RAR-β、RXR-β、RXR-γ、RC3和tTG mRNA的表达。结果（1）穿梭箱主动回避反应实验达到学会标准的训练次数：MVAD组[（45．6±12．1）次]，多于正常对照组[（17．1±4．4）次]（P〈0．01），VAI1组[（20．8±3．1）次]和VA12组[（22．1±4．0）次]均少于MVAD组（P〈0．01），VAI1组和VA12组比较及分别与正常对照组比较，差异均无统计学意义（P〉0．05）；（2）海马脑片诱发LTP的场兴奋性突触后电位（fEPSP）斜率增加的百分比：MVAD组[（22．9±9．4）％]和VAI2组[（39．1±4．3）％]均小于正常对照组[（57．5±27．3）％]（P〈0．05），VAI1组[（51．6±9．4）％]与正常对照组差异无统计学意义；（3）半定量RT-PCR结果：MVAD组的RAR-[3mRNA和RXR-β mRNA表达与对照组比较，分别下降48．72％和37．84％（P均〈0．05），VAI1组RAR-BmRNA表达与MVAD组比较，有增高的趋势（P=0．065）；MVAD组的RC3mRNA表达与对照组比较有降低趋势（P=0．061），MVAD组的RAR-α mRNA表达与对照组比较，有增高趋势（P=0．061）；各组的RXR-γ mRNA和tTG mRNA表?

英文摘要：

Objective In recent years, some experiments on vitamin A-deprived animals reveal a progressive and ultimately profound impairment of hippocampal CA1 area＇s long-term potentiation and these losses are fully reversible by dietary vitamin A replenishment in vivo. Our previous study revealed that marginal vitamin A deficiency （MVAD） beginning from embryonic period impairs learning, memory and long-term potentiation （LTP） in young rats. But the losses might not be reversible if the vitamin A supplementation is late, especially when the critical period of hippocampus development is missed. The present study aimed to observe the recovery of learning and memory in vitamin A marginally deficient young rats after early intervention with vitamin A supplementation and begin to study the mechanism.Methods Rats were divided into control, MVAD, vitamin A intervention 1 （ VAI1 ） and VAI2 groups in this study. In control group （10 young rats） the dams and pups were fed with normal diet（VA 6500 U/kg）. In MVAD group （19 young rats） the dams and pups were fed with MVAD diet（VA 400 U/kg）. In VAIl group （ 10 young rats） the dams were fed with MVAD diet till day 14 of pregnancy, then were fed with normal diet and the pups were fed with normal diet. In VAI2 group （ 13 young rats） the dams were fed with MVAD diet till delivery, then were fed with normal diet and the pups were fed with normal diet too. All the young rats were killed at the age of 7 weeks. During the last week of the experiment, the shuttle box active avoidance reaction tests were carried out. At week 7, the hippocampal CA1 LTP was detected by eleetrophysiological technique. The expression of RAR-α, RAR-β, RXR-β, RXR-γ, RC3 and tTG mRNA was detected by using semi-quantified RT-PCR in hippocampus. Results （1） The times to reach the learning standard in MVAD group （45. 6 ± 12. 1 ） were more than those in control group （ 17.1 ± 4. 4 ） （ P 〈 0. 01 ）, in both VAIl group （20. 8 ± 3. 1 ） and VAI2 group （ 22. 1 ?