Pérez-Gómez Anabel, Tasker R Andrew
Department of Biomedical Sciences, University of Prince Edward Island, 550 University Avenue, Charlottetown, PE, C1A 4P3, Canada.
Neurotox Res. 2014 May;25(4):402-10. doi: 10.1007/s12640-013-9450-z. Epub 2013 Dec 18.
We have previously reported evidence of BDNF upregulation and increased neurogenesis in rat organotypic hippocampal slice cultures (OHSC) after a transient excitotoxic injury to the hippocampal CA1 area induced by low concentrations of the AMPA/kainate receptor agonist domoic acid (DOM). The changes observed in OHSC were consistent with observations in vivo, where low concentrations of DOM administered to rats during perinatal development caused increased BDNF and TrkB expression in the resulting adult animals. The in vivo low dose-DOM treatment also results in permanent alterations in hippocampal structure and function, including abnormal formation of dentate granule cell axons projecting to area CA3 (mossy fiber sprouting). Our objective in the current study is to determine if low concentrations of DOM induce mossy fiber sprouting and/or synaptogenesis in OHSC in order to facilitate future studies on the mechanisms of structural hippocampal plasticity induced by DOM. We report herein that application of a low concentration of DOM (2 μM) for 24 h followed by recovery induced a significant increase in the expression of the mossy fiber marker ZnT3 that progressed over time in culture. The DOM insult (2 μM, 24 h) also resulted in a significant upregulation of both the presynaptic marker synaptophysin and the postsynaptic marker PSD-95. All of the observed effects were fully antagonized by co-administration of the AMPA/kainate antagonists CNQX or NBQX but only partly by the NMDA antagonist CPP and not by the calcium channel blocker nifedipine. We conclude that exposure of OHSC to concentrations of DOM below those required to induce permanent neurotoxicity can induce a progressive change in hippocampal structure that can effectively model DOM effects in vivo.
我们之前曾报道，在低浓度的AMPA/海人酸受体激动剂软骨藻酸（DOM）诱导海马CA1区发生短暂兴奋性毒性损伤后，大鼠脑片培养海马体（OHSC）中脑源性神经营养因子（BDNF）上调且神经发生增加。在OHSC中观察到的这些变化与体内观察结果一致，即在围产期发育期间给大鼠施用低浓度的DOM，会导致成年动物体内BDNF和酪氨酸激酶受体B（TrkB）表达增加。体内低剂量DOM处理还会导致海马结构和功能的永久性改变，包括投射到CA3区的齿状颗粒细胞轴突形成异常（苔藓纤维出芽）。我们在当前研究中的目的是确定低浓度的DOM是否会在OHSC中诱导苔藓纤维出芽和/或突触形成，以便为未来研究DOM诱导海马结构可塑性的机制提供便利。我们在此报告，施用低浓度的DOM（2 μM）24小时后再进行恢复培养，会导致苔藓纤维标志物锌转运体3（ZnT3）的表达随培养时间显著增加。DOM损伤（2 μM，24小时）还导致突触前标志物突触素和突触后标志物突触后密度蛋白95（PSD - 95）均显著上调。所有观察到的效应均可被共同施用AMPA/海人酸拮抗剂CNQX或NBQX完全拮抗，但仅被NMDA拮抗剂氯胺酮部分拮抗，而钙通道阻滞剂硝苯地平则无此作用。我们得出结论，将OHSC暴露于低于诱导永久性神经毒性所需浓度的DOM下，可诱导海马结构的渐进性变化，这能够有效地模拟DOM在体内的作用。
