Inhibitory Mechanisms in Homeostatic Neuronal Plasticity

本研究的目的是深入了解由GAB能抑制中枢神经元的持久变化引起的稳态神经元可塑性的机制。中枢神经系统中兴奋（E）和抑制（I）之间的平衡（E/I平衡）被广泛认为取决于其各个组成部分的微调，从而防止它翻倒。这一提议的总体假设可以总结如下：特异性影响两种类型GABA能抑制（阶段性/突触性和强直性/突触外）之一的变化将导致另一种类型的抑制以及神经元的内在和突触兴奋的明确的稳态变化。最终结果将是兴奋性的整体变化，能够平衡抵消抑制。两种功能上不同的抑制类型的明显变化预计会有差异地抵消E/I平衡，导致 明显不同的代偿性抑制和兴奋性改变。在实验上，这两种类型的抑制将通过药理学、分子生物学或遗传学手段独立地改变。将使用高分辨率电生理学记录在长期器官型切片培养物和从小鼠获得的急性脑切片中研究E/I平衡中产生的偏移。其他实验方法将包括协作解剖学，免疫细胞化学，药理学和分子生物学技术。 E/I平衡中的稳态改变将以高度特异性的方式使用特定GABAA受体（GABAAR）亚基和第二信使系统的适当敲入和敲除小鼠来解决。这些研究将进一步加深我们对中枢神经系统生理可塑性的理解，并将有助于形成旨在预防GABAAR病理可塑性的合理治疗进展的基础。意识到从别构GABAAR调节剂中撤出后的兴奋性惰性，了解神经类固醇、BZ和酒精的作用部位和可塑性，以及对 稳态抑制可塑性将促进用于治疗已知涉及GABA系统的许多严重失能神经和精神障碍的药物发现。我们的研究结果可以为治疗焦虑，压力，苯二氮卓类药物戒断和癫痫的新的和合理的靶向治疗方法提供基础。

The goal of the present proposal is to gain insight into the mechanisms governing homeostatic neuronal plasticity caused by lasting changes in the GAB Aergic inhibition of central neurons. The equilibrium between excitation (E) and inhibition (I) in the CNS (the E/I balance) is widely accepted to depend on the fine-tuning of its individual components, thus preventing it from tipping over. The overall hypothesis of this proposal can be summarized as follows: changes specifically affecting one of the two types of GABAergic inhibition (phasic/synaptic and tonic/extrasynaptic) will result in well-defined homeostatic changes in the other type of inhibition and in the intrinsic and synaptic excitation of neurons. The end result will be an overall change in excitability capable of balancing out the offset inhibition. Distinct changes in the two functionally separate types of inhibition are expected to differentially offset the E/I balance resulting in markedly different compensatory inhibitory and excitatory alterations. Experimentally, the two types of inhibition will be independently altered by pharmacological, molecular biological or genetic means. The resulting offset in the E/I balance will be studied using high resolution electrophysiological recordings in long-term organotypic slice cultures and acute brain slices obtained from mice. Other experimental approaches will include collaborative anatomical, immunocytochemical, pharmacological, and molecular biological techniques. Homeostatic alterations in the E/I balance will be addressed in a highly specific manner using appropriate knockin and knockout mice for specific GABAA receptor (GABAAR) subunits and second messenger systems. The proposed studies will further our understanding of the physiological plasticity in the CNS, and will help form the basis for therapeutical advances rationally aimed at preventing pathological plasticity of GABAARs. Awareness of the excitatory inertia following withdrawal from allosteric GABAAR modulators, knowledge about the site of action and plasticity of neurosteroids, BZ and alcohol, and a fundamental understanding of homeostatic inhibitory plasticity will advance drug discovery for the treatment of many severely incapacitating neurological and psychiatric disorders with known involvement of the GABA system. Our findings could provide the basis for novel and rationally targeted therapeutical approaches for the cure of anxiety, stress, benzodiazepine withdrawal, and epilepsy.