Modulation of Neocortical Interneuronal Function

描述（由申请人提供）：控制大脑皮层兴奋性和抑制性突触传递的突触前机制在正常的信息处理中起关键作用，也可能参与多种脑部疾病的病理生理，如认知能力下降和癫痫。这些实验的具体目的主要集中在含有γ -氨基丁酸（GABA）的抑制性中间神经元介导的抑制性突触传递及其在正常大脑皮层和创伤后癫痫发生模型中三种有效且普遍存在的过程中的调节。这些神经元很容易受到伤害。具体目的涉及：(1)通过突触前Ca++通道控制递质释放；（2,3）神经肽Y和GABA对其受体的作用以及选择性Ca++电流阻滞剂对主要抑制性中间神经元突触前末端产生的GABA能抑制的调节作用。所采用的技术包括使用全细胞膜片钳记录由体外脑切片中鉴定的中间神经元亚类产生的自发和诱发抑制性突触后电流（IPSCs）；激光扫描光刺激绘制皮层连通性；配对记录检查从中间神经元到其他中间神经元和锥体细胞的单一IPSCs；在特定中间神经元物种中使用带有GFP标记的基因工程小鼠；局部应用或灌注受体激动剂和拮抗剂。部分皮质分离模型将用于提供慢性损伤、致癫痫的新皮质切片，并评估这些突触前调节机制的变化，这些机制可能导致高兴奋性。长期目标是确定关键的异常，这些异常可能最终成为选择性药物的目标，用于预防或治疗人类创伤后癫痫。

DESCRIPTION (provided by applicant): Presynaptic mechanisms controlling excitatory and inhibitory synaptic transmission in the cerebral cortex have critical roles in normal information processing and also may contribute to the pathophysiology of a variety of brain disorders such as cognitive decline and epilepsy. The specific aims of these experiments focus primarily on inhibitory synaptic transmission mediated by gamma-amino butyric acid (GABA)-containing inhibitory interneurons and its regulation by 3 potent and ubiquitous processes in normal cerebral cortex and in a model of posttraumatic epileptogenesis. These neurons are known to be vulnerable to injury. Specific aims relate to (1) control of transmitter release by presynaptic Ca++ channels and (2,3) modulatory effects on GABAergic inhibition produced by actions of neuropeptide Y and GABA at their receptors and selective Ca++ current blockers on presynaptic terminals of major classes of inhibitory interneurons. Techniques employed include use of whole cell patch clamp recordings of spontaneous and evoked inhibitory postsynaptic currents (IPSCs) generated by identified subclasses of interneurons in in vitro brain slices; laser scanning photostimulation to map cortical connectivity; paired recordings to examine unitary IPSCs from interneurons to other interneurons and pyramidal cells; use of genetically engineered mice with GFP label in specific interneuron species; and local application or bath perfusion of receptor agonists and antagonists. The partial cortical isolation model will be used to provide chronically injured, epileptogenic neocortical slices and assess changes in these presynaptic modulatory mechanisms that might contribute to hyperexcitability. The long term goals are to identify critical abnormalities that might eventually be targets for selective agents that would used to prevent or treat human posttraumatic epilepsy. PUBLIC HEALTH RELEVANCE: Epilepsy following brain injury is a major health problem. The mechanisms that lead from injury to epilepsy in man are poorly understood however loss of the ability to inhibit or "quiet" nerve cells with the chemical messenger, GABA, is one key underlying factor. The proposed experiments will use a model of posttraumatic epilepsy to better understand how nerve cells regulate GABA release in normal and injured brain, what might go wrong after brain injury, and how that knowledge might be used to improve approaches for prevention and treatment of epilepsy.