染铝对断乳大鼠学习记忆及海马细胞内Ca2＋及磷脂酶和N-甲基-D-天冬氨酸受体α表达的影响

Effect of aluminum on Ca2＋ concentration and expression of phospholipase C and NMDA receptor α genes in hippocampus of weaning rats as well as their neural behavior through subchronic exposure

目的 研究亚慢性染铝对断乳大鼠学习记忆和海马细胞内Ca2＋及磷脂酶C（phospholipase C,PLC）、N-甲基-D-天冬氨酸受体α（NMDARα）表达的影响,以探讨铝损伤发育中大鼠学习记忆的可能机制.方法 刚断乳Wistar大鼠40只,随机分为4组：对照组、低剂量组（饮用含0.2%AlCl3的蒸馏水溶液）、中剂量组（饮用含0.4%AlCl3的蒸馏水溶液）、高剂量组（饮用含0.6%AlCl3的蒸馏水溶液）,每组10只.通过饮水亚慢性连续染毒90 d,跳台试验检测仔鼠学习记忆能力,荧光分光光度计法测定细胞内Ca2＋浓度,免疫印迹（Western blot）法测定PLC、NMDARα的表达.结果 随着染铝剂量的增加,大鼠跳台试验的潜伏期明显缩短,低、中、高剂量组分别为（232.20±57.45）、（35.00±9.37）、（16.10±5.57）s,而错误次数明显增加,低、中、高剂量组分别为（1.10±0.74）、（2.20±0.92）、（3.40±1.51）次,与对照组[分别为（300.00±0.00）s、（0.00±0.00）次]比较,差异均有统计学意义（P〈0.05）;而海马细胞内[Ca2＋]i浓度明显下降,差异亦有统计学意义（P〈0.05）;低、中、高剂量铝暴露组PLC、NMDARα的表达水平分别为0.30±0.06、0.18±0.04、0.16±0.03,0.38±0.03、0.32±0.02、0.25±0.02,较对照组（分别为0.47±0.07、0.48±0.04）明显降低,差异均有统计学意义（P〈0.01）.结论 亚慢性铝暴露可以引起发育中学习记忆能力的损害,抑制NMDARα及PLC的表达,降低海马细胞内Ca2＋水平,推测Ca2＋信号系统的紊乱可能是铝损害学习记忆能力的机制之一.

Objective To estimate the effect of aluminum on hippocampal intracellular Ca2＋ concentration and expression of phospholipase C （PLC） and NMDA receptor α （NMDARα） genes in hippocampus as well as the neural behaviors in weaning rats through subchronic exposure in order to explore the mechanism which aluminum impaired the ability of learning and memory of central nervous system development. Methods Weaning Wistar rats were randomly divided into four groups based on their body weight. Aluminium chloride was administered by water at the doses of 0.2%, 0.4% and 0.6% （m/v） for 90 days. Platform experiment was used to detect the activity of learning and memory. Fura-2/AM calcium ions fluorescence indicator was used to measure Ca2＋ concentration in hippocampal neurons. Western blot method was used to detect the expressions of PLC and NMDARα genes. Results The incubation of rats in platform experiment [（232.20±57.45）, （ 35.00±9.37 ）, （16.10±5.57） s] shortened while increase of mistake times （1.10±0.74, 2.20±0.92,3.40± 1.51 ） was significantly associated with the dose of aluminum （P〈0.01 ）. The Ca2＋ concentration decreased significantly in the rats of aluminum exposed groups （P〈0.01）. The expression of PLC and NMDARα in aluminum exposed groups （0.30±0.06, 0.18±0.04, 0.16±0.03 ; 0.38±0.03, 0.32±0.02, 0.25±0.02） decreased significantly compared with that in the control group （0.47±0.07,0.48±0.04） （P〈0.01 ） and there was a dose-effect relationship in the NMDARα expression. Conclusion Subchronic exposure of aluminium could impair the ability of learning and memory in rats during development, inhibit the expression of NMDARα and PLC and reduce Ca2＋ concentration, suggesting that the disorder of Ca2＋ signaling system might be one of mechanisms of aluminium damaging the ability of learning and memory.