脑发育不同阶段慢性铅暴露对大鼠在体海马齿状回LTP的影响

目的和方法：探讨脑发育不同阶段慢性铅暴露对在体海马ＬＴＰ的影响。应用细胞外微电极记录单脉冲刺激穿通路纤维在海马齿状回诱发的群体锋电位（ＰＳ），观察母体期、断乳后及出生前后持续性慢性铅暴露大鼠于高频刺激（ＨＦＳ）前后的ＰＳ幅值变化，并与对照组相比较。结果：ＨＦＳ前，基线记录的各铅暴露组ＰＳ平均幅值及峰潜伏期与对照组无显著差异；ＨＦＳ后，各铅暴露组ＬＴＰ发生率虽与对照组无显著差异，但铅暴露组的ＬＴＰ增幅减小，并出现了短时增强转为抑制及ＬＴＤ型反应。统计显示各铅暴露组ＨＦＳ后ＰＳ振幅的平均增强率显著低于对照组：对照组平均增强至基线值的１３８．２％，母体期铅暴露组为基线值的１０８．８％，断乳后铅暴露组为基线值的１０７．８％，持续铅暴露组为基线值的１０４．４％。结论：脑发育任一阶段的慢性铅暴露均可损害海马ＬＴＰ的在体诱导和维持，且以维持过程受损为主；与发育成熟海马相比，未成熟期海马对铅的神经毒性更为敏感，突触可塑性更易受损。

EFFECT OF CHRONIC LEAD EXPOSURE AT BRAIN DIFFERENT DEVELOPMENTAL STAGES ON LONG TERM POTENTIATION IN RAT HIPPOCAMPAL DENTATE GYRUS IN VIVO

Aim and Methods: To investigate the effects of chronic lead exposure at brain different developmental stages on long term potentiation (LTP) in rat hippocampal dentate gyrus (DG) in vivo. Population spikes (PS) were recorded in the DG in response to single pulse stimulation applied to perforant path (PP) with extracellular microelectrode technique. We observed the changes of PS amplitude before and after the application of high frequency stimulation (HFS) of maternally, postweaningly, permanently (i.e. pre and postnatally) lead exposed male Wistar offspring and controls, respectively. Results: The baseline recordings of PS evoked by single pulse stimulation revealed no differences between the control and the three Pb exposed groups with respect to the mean PS amplitude and peak latency. After HFS, the difference in incidence of LTP induction in control and all three Pb exposed groups was also statistically non significant. However, the increase in relation to the baseline values (100%) of mean PS amplitude after HFS in each Pb exposed group was markedly smaller than in the control group: in the control group, the mean PS amplitude increased to 138.2% from the baseline values; in the maternally exposed group, to 108.8%; in the postweaningly exposed group, to 107.8%; in permanently group, to 104.4%. Conclusion: Chronic lead exposure during brain any developmental stage may impair LTP in vivo and the immature hippocampus might be higher vulnerable as compared with the mature one to lead neurotoxicity.