EXCITABILITY OF DEGENERATING NEURONS IN EPILEPSY

人们普遍认为，海马区的超兴奋性和细胞 变性常与颞叶癫痫并存。树突棘 丧失和肿胀通常表现在癫痫组织中，并且 在一些实验模型中也产生了癫痫。最近 对人类癫痫海马片的研究表明，癫痫的发病率很高 致痫突触传递在其树突为 病理性的改变。这一证据表明，树突 变性，癫痫病理的特征，并不一定 伴随着对突触输入的低反应性。发送到 相反，在它们的病理发展过程中，这样 形态变化可能会创造一种加速细胞生长的环境 原位癫痫发作背后的神经元兴奋性。 我计划用匹罗卡品治疗颞叶癫痫的模型来测试 上述假设。初步研究表明，齿状颗粒 匹罗卡品处理大鼠的细胞(DGC)具有相似的形态 它们的树突与人类癫痫患者报告的树突变化相同 海马体，即脊柱形状的变化，脊柱的丢失和不规则的骨干 由于肿胀。这些神经元的神经生理记录 在穿通径突触传递中显示出高兴奋性。 利用细胞内记录技术，细胞内细胞 染色、全细胞膜片钳记录和微应用 海马片中的神经递质激动剂，我将1)测定 树突状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 还有药理上的。不同突触电流的作用将是 在产生增强的突触反应方面进行了评估 匹罗卡品处理的DGC。3)NMDA-EPSCs对细胞的影响 随后的GABA-A IPSCs将被研究。正常大鼠海马区 切片，细胞内钙离子浓度升高可下调 GABA-A受体的功能。我将测试这种可能性在 树突状退行性变的DGC，其中NMDA反应增强 观察到的。增加的NMDA反应可能会提升细胞内 钙水平异常，可能促进钙的调节 毛果芸香碱对DGCs GABA-A受体功能的影响在……里面 匹罗卡品DGC、GABA-A电流在增加时可能暂时丧失 产生NMDA电流。4)枝晶变形将被量化 通过计算定义节段内的脊椎数量并通过测量 树枝状结构域。这些发现将与上述情况相关联 生理上的发现。这决定了突触的敏感性 树突状变性神经元的可塑性。加在一起，这些 实验将为更全面地理解 癫痫树突状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.