Abstract：
OBJECTIVE: Pathological forms of neural activity, such as epileptic seizures, modify the expression pattern of multiple proteins, leading to persistent changes in brain function. One such protein is activity-regulated cytoskeleton-associated protein (Arc), which is critically involved in protein-synthesis-dependent synaptic plasticity underlying learning and memory. In the present study, we have investigated how the expression of ArcKR, a form of Arc in which the ubiquitination sites have been mutated, resulting in slowed Arc degradation, modifies group I metabotropic glutamate receptor-mediated long-term depression (G1-mGluR-LTD) following seizures.
METHODS: We used a knock-in mice line that express ArcKR and two hyperexcitation models: an in vitro model, where hippocampal slices were exposed to zero Mg2+, 6 mM K+; and an in vivo model, where kainic acid was injected unilaterally into the hippocampus. In both models, field excitatory postsynaptic potentials (fEPSPs) were recorded from the CA1 region of hippocampal slices in response to Schaffer collateral stimulation and G1-mGluR-LTD was induced chemically with the group 1 mGluR agonist DHPG.
RESULTS: In the in vitro model, ArcKR expression enhanced the effects of seizure activity and increased the magnitude of G1-mGluR LTD, an effect that could be blocked with the mGluR5 antagonist MTEP. In the in vivo model, fEPSPs were significantly smaller in slices from ArcKR mice and were less contaminated by population spikes. In this model, the amount of G1-mGluR-LTD was significantly less in epileptic slices from ArcKR mice as compared to wildtype (WT) mice.
CONCLUSIONS: We have shown that expression of ArcKR, a form of Arc in which degradation is reduced, significantly modulates the magnitude of G1-mGluR-LTD following epileptic seizures. However, the effect of ArcKR on LTD depends on the epileptic model used, with enhancement of LTD in an in vitro model and a reduction in the kainate mouse model.
METHODS: We used a knock-in mice line that express ArcKR and two hyperexcitation models: an in vitro model, where hippocampal slices were exposed to zero Mg2+, 6 mM K+; and an in vivo model, where kainic acid was injected unilaterally into the hippocampus. In both models, field excitatory postsynaptic potentials (fEPSPs) were recorded from the CA1 region of hippocampal slices in response to Schaffer collateral stimulation and G1-mGluR-LTD was induced chemically with the group 1 mGluR agonist DHPG.
RESULTS: In the in vitro model, ArcKR expression enhanced the effects of seizure activity and increased the magnitude of G1-mGluR LTD, an effect that could be blocked with the mGluR5 antagonist MTEP. In the in vivo model, fEPSPs were significantly smaller in slices from ArcKR mice and were less contaminated by population spikes. In this model, the amount of G1-mGluR-LTD was significantly less in epileptic slices from ArcKR mice as compared to wildtype (WT) mice.
CONCLUSIONS: We have shown that expression of ArcKR, a form of Arc in which degradation is reduced, significantly modulates the magnitude of G1-mGluR-LTD following epileptic seizures. However, the effect of ArcKR on LTD depends on the epileptic model used, with enhancement of LTD in an in vitro model and a reduction in the kainate mouse model.
摘要：
目的：神经活动的病理形式，比如癫痫发作，改变多种蛋白质的表达模式，导致大脑功能的持续变化。一种这样的蛋白质是活性调节的细胞骨架相关蛋白（Arc），这与学习和记忆背后的蛋白质合成依赖性突触可塑性密切相关。在本研究中,我们已经研究了ArcKR的表达，泛素化位点发生突变的电弧形式,导致电弧降解减慢，改变I组代谢型谷氨酸受体介导的癫痫发作后长期抑郁(G1-mGluR-LTD)。
方法：我们使用了表达ArcKR的敲入小鼠系和两种超兴奋模型：一种体外模型，海马切片暴露于零Mg2+，6mMK+；和体内模型，在海马中单侧注射了海藻酸。在这两种模型中，响应于Schaffer侧支刺激，从海马切片的CA1区域记录场兴奋性突触后电位（fEPSP），并用第1组mGluR激动剂DHPG化学诱导G1-mGluR-LTD。
结果：在体外模型中，ArcKR表达增强了癫痫发作活性的作用，并增加了G1-mGluRLTD的大小，可以用mGluR5拮抗剂MTEP阻断的作用。在体内模型中,在ArcKR小鼠的切片中，fEPSP明显较小，并且受种群尖峰的污染较少。在这个模型中,与野生型(WT)小鼠相比,来自ArcKR小鼠的癫痫切片中G1-mGluR-LTD的量显著更少。
结论：我们已经表明ArcKR的表达，一种减少降解的电弧形式，癫痫发作后显着调节G1-mGluR-LTD的大小。然而,ArcKR对LTD的影响取决于所使用的癫痫模型，随着LTD在体外模型中的增强和红藻氨酸小鼠模型中的减少。
方法：我们使用了表达ArcKR的敲入小鼠系和两种超兴奋模型：一种体外模型，海马切片暴露于零Mg2+，6mMK+；和体内模型，在海马中单侧注射了海藻酸。在这两种模型中，响应于Schaffer侧支刺激，从海马切片的CA1区域记录场兴奋性突触后电位（fEPSP），并用第1组mGluR激动剂DHPG化学诱导G1-mGluR-LTD。
结果：在体外模型中，ArcKR表达增强了癫痫发作活性的作用，并增加了G1-mGluRLTD的大小，可以用mGluR5拮抗剂MTEP阻断的作用。在体内模型中,在ArcKR小鼠的切片中，fEPSP明显较小，并且受种群尖峰的污染较少。在这个模型中,与野生型(WT)小鼠相比,来自ArcKR小鼠的癫痫切片中G1-mGluR-LTD的量显著更少。
结论：我们已经表明ArcKR的表达，一种减少降解的电弧形式，癫痫发作后显着调节G1-mGluR-LTD的大小。然而,ArcKR对LTD的影响取决于所使用的癫痫模型，随着LTD在体外模型中的增强和红藻氨酸小鼠模型中的减少。
