出生后铅暴露对大鼠海马突触结构可塑性的影响

Effect of lead exprosure on synaptic structural plasticity in the hippocampus of postnatal Wistar rat

目的通过观察断乳后染毒Wistar大鼠海马神经元数目、突触数目以及突触结构参数:突触间隙宽度、突触后致密物厚度、突触活性带长度、突触界面曲率的变化情况,探讨出生后铅暴露对海马突触结构可塑性的影响。方法断乳后雌性大鼠16只,随机分成染铅组和对照组各8只。染铅组经水给予400μmol/L PbCl2,对照组饮用去离子水,直至观察终点(2月龄),T迷宫学习训练后灌注取脑,应用免疫组化法检测神经元数目,利用透射电镜测定突触数目及突触结构参数。结果与对照组相比,染铅组血铅显著增高(P<0.05);染铅组大鼠脑海马CA3区神经元数目与对照组神经元细胞数目无显著差异(P>0.05);染铅组与对照组相比,大鼠脑海马CA1区突触数目显著减少(P<0.05),突触结构参数中:间隙宽度显著增大(P<0.05),突触后致密物厚度、突触界面曲率及突触活性带长度显著减小(P<0.05)。结论断乳后低剂量的铅染毒并不对大鼠海马神经元的数目产生影响,而是主要引起突触连接数目的减少以及突触间隙、突触后致密物厚度等突触结构参数的改变,从而对学习记忆造成影响。

Objective To study the effect of lead exposure on synaptic structural plasticity in the hippocampus of postnatal Wistar rats by observing the change of neurons number, the number of synapses and synaptic structural parameters including synaptic cleft, the thinkness of postsynaptic density, synaptic curvature and the width of synaptic active zone. Methods Wistar rats, after lactation, 16 pub rats were divided into test group and control group. The test group was given lead dichloride 400μmol/L by drinking water while the control group with distill water till 2 month old. The hippocampus was taken out after T maze test which was employed to excise their spatial learning and memory ability. Immunohistochemistry method was used to determine the amount of neurons. The number of synapses and the features of synaptic strutural parameters were measured by transmission electron microscope. Results The blood lead level of the test group was significantly higher than that of the control group （P 〈 0.05）. There was no significantdifference between the two groups in the amount of neurons in the CA3 region of hippoeampus （P 〉 0.05）. Compared with the control group, the number of synapses in the test group was reduced （P 〈 0.05）. Among the synaptic strutural parameters, the results revealed a significant increase in the synaptic cleft（P 〈 0.05 ） , while the thinkness of postsynaptic density, synaptic curvature and the width of synaptic active zone were significantly reduced （P 〈 0.05 ） comparing the normal control group respectively. Conclusion Lead exposure of low dose affect spatial learning and memory ability in postnatal life not on the amount of hippocampus neurons, but reducing the number of synapses and changing the synaptic parameters, such as the thinkness of postsynaptic density, synaptic curvature and the width of synaptic active zone.