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14 d,后改饲VA充足饲料,幼鼠饲VA充足饲料。VAI2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VAI2组[(22.1±4.0)次]均少于MVAD组(P<0.01),VAI1组和VAI2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-βmRNA和RXR-βmRNA表达与对照组比较,分别下降48.72%和37.84%(P均<0.05),VAI1组RAR-βmRNA表达与MVAD组比较,有增高的趋势(P=0.065);MVAD组的RC3 mRNA表达与对照组比较有降低趋势(P=0.061),MVAD组的RAR-αmRNA表达与对照组比较,有增高趋势(P=0.061);各组的RXR-γmRNA和tTG mRNA表达无明显差异(P>0.05)。结论早期VA干预可以使MVAD所致的学习记忆障碍行为基本恢复至正常水平,而新生干预不能使LTP恢复正常;VA可能主要通过受体RARα-、RAR-β和RXR-β调控RC3的表达,影响海马长时程增强,最终表现为学习记忆的改变。
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 ± 4. 0 ） were more than those in group MVAD （ P 〈 0. 01 ） , and there were no significant differences among groups VAIl, VAI2 and control （ P 〉 0. 05 ） in active avoidance reaction tests. （2） The changes of field excitatory postsynaptic potentials （fEPSP） slope for MVAD group [ （22. 9 ±9. 4）% ] and VAL2 group [ （39. 1 ±4. 33）% ] were less than that of control group [ （57. 5 ± 27.3 ） % ], respectively （ P 〈 0. 05 ）. No significant difference was found between VAIl and control group （P 〉0. 05）. （3） The expression of RAR-β and RXR-β mRNA decreased by 48. 72% and 37.84% respectively （P 〈 0.05 ） compared with control, but the expression of RAR-I3 mRNA in group VAIl was higher than that in group MVAD（P =0. 065）. The expression of RC3 mRNA in MVAD group was lower than that in control （P =0.061 ） and RAR-α mRNA in MVAD group was higher than that in control （P =0. 061 ）. The expression of RXR-γ and tTG mRNA had no significant difference among different groups as determined with semi-quantified RT-PCR in hippocampus. Conclusion Early vitamin A intervention may make the impaired learning and memory behavior due to marginal vitamin A deficiency recover to the normal level in young rats, but lip losses in group VAI2 might not be reversible. Vitamin A may modulate the expression of RC3 mRNA by affecting RAR-α, RAR-β and RXR-β to influence the LTP, learning and memory.
出处
《中华儿科杂志》
CAS
CSCD
北大核心
2006年第1期15-20,共6页
Chinese Journal of Pediatrics
基金
国家自然科学基金资助项目(30471462)
关键词
大鼠
维生素A缺乏
学习
记忆
Rats
Vitamin A deficiency
Learning
Memory
