Developmental Regulation of Glutamate Receptor Function

 描述（申请人提供）：在大脑内的大多数兴奋性通路中，即由神经递质谷氨酸介导的那些，对谷氨酸受体功能的电生理学和分子解剖学研究，使人们对会聚的发育轴突之间的相对相关活动如何通过NMDA受体（NR）介导发育输入的加强和稳定有了深入的了解以及其驱动突触强度的长时程增强（LTP）的能力。NR-LTP加强初始的突触时，他们传输的活动是相关的时间。这已经建立了特定的NR的化学拮抗剂，以及在几个神经制剂的活动模式的实验操作。然而，不知道是否差 通过NR-LTD的相关轴突活性减弱了发育中的许多不精确靶向的谷氨酸介导的连接和一些成熟但患病或受损的途径。例如，未精确的中央投射可能会保留儿童未矫正的弱视，长期白内障阻碍高保真视觉或视神经损伤。 即使在小鼠模型中，也很难通过实验确定异常NR-LTD是否也参与这些病症，因为NR的拮抗剂阻断NR-LTP以及NR-LTD。在我们的最后一个NEI资助期，我们开发了针对SAP 102或PSD-95的短发环shRNA，其严重减少或消除了这些NR突触支架。我们发现，在小鼠中，在睁眼后不久，在来自单个视觉皮层（VC）神经元的切片记录中，SAP102KD消除了NR-LTD，但使NR-LTP在第2/3层VC细胞中不受影响。我们在来自睁眼后小鼠幼仔VC神经元的切片中获得了类似的结果，这些神经元感染了携带不同修饰的HSV，这些修饰破坏了NR的正常GluN2A或2B亚基组成。我们还一直在研究一种突变小鼠Flailer，它缺乏NR-LTD，但保留了VC和上级丘中的NR-LTP。在本申请中，我们提出使用各种解剖学、电生理学和光学记录技术，沿着对上述方法和Flailer小鼠的一些修改，Flailer小鼠最初是为了不相关的实验而获得的，以确定在发育中的突触连接中，缺乏NR-LTD的年轻神经元是否可以细化VC中整个视觉通路的发育中的视觉投射，上级丘和外侧膝状体背侧核。

 DESCRIPTION (provided by applicant): In the majority of excitatory pathways within the brain, namely those mediated by the neurotransmitter glutamate, the electrophysiological and molecular dissection of glutamate receptor function has led to a sophisticated understanding of how relatively correlated activity among converging developing axons can mediate strengthening and stabilization of developing inputs via the NMDA receptor (NR) and its ability to drive long term potentiation of synaptic strength (LTP). NR-LTP strengthens initial glutamatergic synapses when the activity they transmit is correlated in time. This has been established with chemical antagonists specific to the NR as well as by experimental manipulation of activity pattern in several neural preparations. However, it is not known if poorly correlated axon activity via NR-LTD weakens the many imprecisely targeted glutamate- mediated connections in developing and some mature but diseased or damaged pathways. For example, unrefined central projections are likely to be retained with uncorrected amblyopia in children, with long-term cataract obstruction of high fidelity vision or damage to the optic nerve. Whether or not abnormal NR-LTD is also involved in these conditions is hard to determine experimentally even in mouse models because antagonists of NRs block NR-LTP as well as NR-LTD. In our last NEI funding period we developed short- hairloop shRNAs against either SAP102 or PSD-95 that severely reduced or eliminated these NR synaptic scaffolds. We found that in slice recordings from single visual cortex (VC) neurons, in mice shortly after eye- opening, that SAP102KDs eliminated NR-LTD but left NR-LTP un-effected in layer 2/3 VC cells. We achieved similar results in slices from post-eye opening mouse pup VC neurons that were infected with HSV carrying different carrying different modifications that disrupted either the normal GluN2A or 2B subunit composition of the of NRs. We also have been working on a mutant mouse Flailer that lacks NR-LTD but retains NR-LTP in VC and Superior Colliculus. In this current application we propose to use a variety of anatomical, electrophysiological, and optical recording techniques, along with some modifications to the approaches described above and the Flailer mouse, that was obtained initially for unrelated experiments, to determine if, in developmenting synaptic connections young neurons lacking NR-LTD can refine the developing visual projections throughout the visual pathway in VC, Superior Colliculus and the dorsal lateral geniculate nucleus.