CHARACTERIZATION OF INTRINSIC VISUAL CORTICAL NEURONS

哺乳动物大脑皮层和大鼠初级视皮层(第17区) 具体地说，它既包含外源性神经元，也包含内在神经元。三叉神经轴突 外在细胞在区域17内终止，但也在区域17外终止。 另一方面，固有轴突只与该区域内的靶点相连。 ；这种单元格类型经常与 被认为对正常皮质至关重要的抑制作用 功能。拟议研究的目的是描述 内源性神经元的形态和化学类型，并评估 已识别细胞在大脑皮层回路中的作用。为了实现这些目标， 解剖示踪和免疫细胞化学技术将用于 与一种新的强大的逆行标记方法相结合 在体外可视化局部投射神经元。这些组合方法 将允许细胞内电生理记录和染色 对已识别的内源性皮质神经元进行注射 组织切片。在最初的实验中，将特别强调 放在几种固有细胞类型的特征上，我们 以前在深层的膝状输入区识别过。 这些类型对GABA能标志物进行染色，尽管它们在 它们对生长抑素的共定位，因此可能允许区分 两个内在的，假定的抑制系统。对这两个问题的分析 系统将关注其细胞体的空间分布，即 垂直和水平层流轴突投射模式，空间 与传入和传出投射系统的关系及其 对上层GABA能级晶格的贡献。下层6 接受丘脑和大脑皮层的传入，可能至少 这些内在系统中的一个提供单突触输入。细胞内 来自深层6中已识别单元格的记录将在 以确定准确的关系。检查突触后 起源于深层6的不同内在途径的影响，我们 将记录不同大脑皮层对刺激的反应 第六层。此外，我们将调查GABA作为 一些内在神经元中的神经递质。双电极 实验，结合细胞内染料注射和 免疫细胞化学，将尝试识别抑制性神经元的类型 并确定它们如何集成到内部电路中。 这些解剖学和免疫细胞化学研究应该有助于 对内在皮质系统的组织的理解(S)，其中 以及它们如何处理传入的兴奋性活动，因此， 它们如何提供神经元反应特性。生理学 此外，实验还应允许测定和表征 这些抑制性神经元的突触反应及其 突触后靶点。

Mammalian cerebral cortex and rat primary visual cortex (area 17) specifically, contain both extrinsic and intrinsic neurons. Axons of extrinsic cells terminate within, but also outside area 17. Cells with intrinsic axons, on the other hand, only connect to targets within the area in which they reside; this cell type has frequently been associated with inhibitory actions which are thought to be crucial for normal cortical functions. The aim of the proposed research are to characterize the morphological and chemical types of intrinsic neurons and to assess the role of identified cells in cortical circuitry. To achieve these goals, anatomical tracing and immunocytochemical techniques will be used in combination with a new and powerful retrograde labeling method for visualizing local projection neurons in vitro. These combined approaches will permit intracellulr electro-physiological recordings and dye injections to be performed on identified, intrinsic cortical neurons in tissue slices. In the initial experiments, particular emphasis will be placed on the characterization of several intrinsic cell types which we previously identified in the geniculate input zone in deep layer 6. Two of these types stain for GABAergic markers, although they probably differ in their colocalization for somatostatin and, thus, may permit the distinction of two intrinsic, putative inhibitory systems. Analysis of these two systems will focus on the spatial distribution of their cell bodies, the vertical and horizontal laminar axonal projection patterns, the spatial relationships to afferent and efferent projection systems and their contribution to a GABAergic lattice in upper layers. Lower layer 6 receives thalamic and cortical afferents and, it is possible that at least one of these intrinsic systems provides monosynaptic input. Intracellular recordings from identified cells in deep layer 6 will, be performed, in order to determine the precise relationships. To examine the postsynaptic effects of the different intrinsic pathways originating in deep layer 6, we will record the responses in different cortical layers to stimulation of layer 6. In addition, we will investigate the possibility that GABA acts as neurotransmitter in some of the intrinsic neurons. Two-electrode experiments, combined with intracellular dye injections and immunocytochemistry, will attempt to identify types of inhibitory neurons and to determine how they are integrated into the intrinsic circuitry. These anatomical and immunocytochemical studies should contribute to the understanding of the organization of intrinsic, cortical system(s), where and how they act to process incoming excitatory activity and, therefore, how they provide for neuronal response properties. The physiological experiments should, in addition, permit determination and characterization of the synaptic responses of these inhibitory neurons and their postsynaptic targets.