Effects of TrkB Activation on Abnormalities in Neocortical FS interneuron

小白蛋白(PV)和生长抑素(SOM)中间神经元异常在许多 神经紊乱，包括癫痫。改善有缺陷的中间神经元功能的疗法不是 可用。中间神经元的结构发育和维持依赖于提供的营养支持 通过脑源性神经营养因子(BDNF)激活TrkB受体。在底切(UC)模型中 癫痫样新皮质损伤，选择性小分子部分激动剂对TrkB-Rs的慢性激活 (LM22A-4，下文“LM”)对逆转抑制性脑结构和功能异常具有长期作用。 PV中间神经元终末促进GABA释放并提高致痫阈值 活动和癫痫发作。为了确定这些影响是否适用于治疗或预防 癫痫的不同原因在其他模型中的发生率，例如遗传性癫痫、Dravet综合征 (DS)小鼠将用于一些实验。PV中间神经元膜钠通道的减少 在DS小鼠中导致抑制性递质GABA的释放减少，并发展为自发性 以及高温导致的癫痫发作。将在DS和UC小鼠中使用各种实验方法 通过增加SOM神经末梢的GABA释放来确定长期服用LM是否 而PV中间神经元，或诱导新的抑制性突触形成，将加强对皮质网络的抑制 和抑制癫痫样放电：1)免疫细胞化学和共聚焦成像将用于评估 PV和SOM突触前终末的变化，包括VGAT-和GAD65/67-的表达变化 IR和钙感受器蛋白突触素2)；2)SOM/-和PV/Gen-Close的密度分析 检测TrkB激活诱导的新的抑制性突触形成；3)电生理学 丘脑室旁核中间神经元向锥体神经元抑制性突触传递的基本特性分析 体外切片检测TrkB激活对单一IPSCs、释放概率和传递失败的影响； 3)对PV/ChR2和SOM/ChR2小鼠大脑皮层切片进行激光扫描光刺激，以定位 新皮质抑制环路中抑制连接的分布和强度；4)视频/脑电监测 评价灯盏细辛治疗对自发性癫痫发作和高温诱导的影响 癫痫发作。这些实验的结果将提供关于神经元间质导致的机制的信息。 癫痫的异常发展和预防癫痫发生的潜在途径 增强中间神经元的营养支持。

Abnormalities in parvalbumin (PV) and somatostatin (SOM) interneurons are reported in a number of neurological disorders, including epilepsy. Therapy that improves function of defective interneurons is not available. Structural development and maintenance of interneurons is dependent on trophic support provided by brain derived neurotrophic factor (BDNF) activation of TrkB receptors. In the undercut (UC) model of epileptogenic neocortical injury, chronic activation of TrkB-Rs with a selective small molecule partial agonist (LM22A-4, “LM” below) has long-term effects to reverse structural and functional abnormalities in inhibitory terminals of PV interneurons, enhance GABA release and increase the threshold for evoking epileptiform activity and seizures. In order to determine whether these effects will be applicable to treatment or prevention of epilepsy in other models with different causes for seizures, such as genetic epilepsies, the Dravet syndrome (DS) mouse will be used in some experiments. Decreases in a membrane sodium channel in PV interneurons in DS mice causes decreased release of the inhibitory transmitter GABA, and development of spontaneous and high temperature-induced seizures. A variety of experimental approaches in DS and UC mice will be used to determine whether chronic treatment with LM, by increasing GABA release from nerve terminals of SOM and PV interneurons, or inducing new inhibitory synapse formation, will enhance inhibition in cortical networks and suppress epileptiform discharges: 1) immunocytochemistry and confocal imaging will be used to assess alterations in PV and SOM presynaptic terminals, including changes in expression of VGAT- and GAD65/67- IR, and the calcium sensor protein synaptotagmin 2; 2) analysis of density of SOM/- and PV/gephyrin close appositions to test for new inhibitory synapse formation induced by TrkB activation; 3) electrophysiological analysis of basic properties of inhibitory synaptic transmission from PV interneurons to pyramidal neurons of in vitro slices to detect effects of TrkB activation on unitary IPSCs, release probability and transmission failures; 3) laser scanning photostimulation of cortical slices from PV/CHR2 and SOM/CHR2 mice to map the distribution and strength of inhibitory connectivity in neocortical inhibitory circuits; and 4) video/EEG monitoring of implanted mice to assess effects of treatment with LM on spontaneous seizures and hyperthermia-induced seizures. Results of these experiments will provide information about mechanisms leading from interneuronal abnormalities to development of epilepsy and a potential approach to prophylaxis of epileptogenesis by enhancing trophic support of interneurons.