EXCITABILITY OF DEGENERATING NEURONS IN EPILEPSY

目前普遍认为海马过度兴奋和细胞凋亡可能与海马神经元的过度兴奋有关。 变性常同时存在于颞叶癫痫中。 树突棘 损失和肿胀通常显示在癫痫组织中， 在一些癫痫的实验模型中也会产生。 最近的一 在人类癫痫海马切片中的研究表明， 致痫性突触传递的神经元的树突是 病理性改变 这一证据表明， 癫痫病理学的特征性变性， 伴随着对突触输入的低反应性。 到 相反，在他们的病理进展过程中， 形态学的变化可能会创造一个细胞环境， 原位癫痫发作的神经元兴奋性。 我计划用匹鲁卡品颞叶癫痫模型来测试 上述假设。 初步研究表明，齿状颗粒 毛果芸香碱处理的大鼠中的DGC细胞（DGC）显示类似的形态学 在他们的树突的变化，以那些报告在人类癫痫 海马，即棘形状的改变、棘丢失和不规则的轴 因为肿胀 这些神经元的神经生理记录 显示在穿通通路突触传递中的过度兴奋。 利用细胞内记录技术， 染色，全细胞膜片钳记录，和微应用 神经递质激动剂在海马切片，我将1）确定 树突变形神经元的固有膜特性，以及 2)电隔离兴奋性和抑制性突触后反应 和。 不同突触电流的作用将是 评估在产生增加的突触反应， 毛果芸香碱处理的DGC。3)NMDA EPSCs对大鼠海马神经元的影响 将研究随后的GABA-A IPSC。 在正常大鼠海马 切片，细胞内钙浓度增加可以下调 GABA-A受体功能。 我将测试这种可能性， 树突退化的DGC，其中增加的NMDA反应是 观察 增加的NMDA反应可能会提高细胞内 钙水平异常，这可能有助于钙的调节 对毛果芸香碱处理的DGC中GABA-A受体功能的影响。 在 毛果芸香碱DGC，GABA-A电流增加时可能暂时丧失 产生NMDA电流。4)将量化树突状畸形 通过计算限定的节段内的棘的数量并通过测量 树突状结构域。 这些发现将与上述相关 生理发现。 这决定了突触的敏感性。 树突退化神经元的可塑性。 所有这些 实验将为更全面地了解 癫痫中树突变性神经元的兴奋性。

It is generally accepted that hippocampal hyperexcitability and cell degeneration often co-exist in temporal lobe epilepsy. Dendritic spine loss and swelling are commonly displayed in epileptic tissue, and are also generated in some of the experimental models of epilepsy. A recent study in human epileptic hippocampal slices demonstrated a high incidence of epileptogenic synaptic transmission in neurons whose dendrites were pathologically altered. This evidence suggests that dendritic degeneration, characteristic of epileptic pathology, may not necessarily be accompanied by hypo-responsiveness to synaptic inputs. To the contrary, in the course of their pathological progression, such morphological changes may create a cellular environment that accelerates the neuronal excitability underlying in situ epileptic seizures. I plan to use the pilocarpine model for temporal lobe epilepsy to test the above hypothesis. Preliminary Studies show that the dentate granule cells (DGCs) in pilocarpine-treated rats display similar morphological alterations in their dendrites to those reported in human epileptic hippocampus, i.e. changes of spine shape, spine loss and irregular shafts due to swelling. Neurophysiological recording from these neurons revealed hyperexcitability in perforant path synaptic transmission. Using the techniques of intracellular recording, intracellular cell staining, whole cell patch clamp recording, and microapplication of neurotransmitter agonists in hippocampal slices, I will 1) determine the intrinsic membrane properties of the dendritically-deformed neurons, and 2) isolate excitatory and inhibitory post synaptic responses electrically and pharmacologically. The role of different synaptic currents will be assessed in generating increased synaptic responses in the pilocarpine-treated DGCs. 3) The effect of the NMDA EPSCs on the subsequent GABA-A IPSCs will be studied. In normal rat hippocampal slices, increased intracellular calcium concentration can down-regulate GABA-A receptor function. I will test this possibility in dendritically-degenerating DGCs where an increased NMDA response is observed. The increased NMDA response likely elevates intracellular calcium level abnormally, which possibly facilitates calcium's modulatory effect on GABA-A receptor function in pilocarpine-treated DGCs. In pilocarpine DGCs, GABA-A current may be temporarily lost when increased NMDA currents are generated. 4) Dendritic deformities will be quantified by counting the number of spines within defined segments and by measuring dendritic domains. These findings will be correlated with the above physiological findings. This determines the sensitivity of synaptic plasticity in dendritically degenerating neurons. Together, these experiments will provide evidence for a fuller understanding of the excitability of dendritically degenerating neurons in epilepsy.