McCurdy M L, Houk J C, Gibson A R
Department of Physiology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
J Comp Neurol. 1998 Mar 2;392(1):115-33.
The purpose of these experiments was to define the topography of cuneate and spinal projections to the forelimb representation in the rostral dorsal accessory olive (rDAO). We were interested in determining whether the spinal and cuneate inputs constitute a homogeneous afferent source, and whether there is evidence that they serve different functional roles. We were also interested in determining whether the somatotopy of rDAO is the result of a point-to-point projection from its afferent sources, or whether the projection suggests a reorganization of afferents at the olive. Single unit recording was used to identify specific regions of rDAO, and the topography of inputs to the identified regions was determined by using wheat germ agglutinin-horseradish peroxidase (WGA-HRP) as a tracer. The results from retrograde tracing were confirmed by using WGA-HRP as an anterograde tracer from input sources. The cuneate and spinal neurons providing input to rDAO constitute two distinct neural populations. One consists of cells in the caudal cuneate nucleus and lamina VI of the rostral two cervical segments, the other consists of cells in the rostral cuneate nucleus. The cells in the caudal cuneate nucleus and the rostral cervical segments are large, multipolar neurons that form a single column of rDAO input cells. The column of cells projects to the contralateral rDAO in a topographic fashion with rostral regions of the column projecting to rostral rDAO, which contains cells that respond to somatosensory stimulation of the contralateral shoulder, trunk, and proximal forelimb. Caudal regions of the column project to caudal rDAO, which contains cells that respond to stimulation of the distal forelimb. Despite this topography, there is a large degree of overlap in the terminations from neighboring regions of the input column, indicating that a major reorganization occurs at the rDAO. The projection from the rostral cuneate nucleus arises from small neurons that project bilaterally to rDAO, and the input from the rostral cuneate nucleus lacks a clear topography. We propose that input from the cell column is responsible for the somatosensory sensitivity of rDAO neurons, whereas input from rostral cuneate is most likely modulatory, probably inhibitory, in nature.
这些实验的目的是确定楔束和脊髓投射至吻侧背副橄榄核（rDAO）中前肢代表区的局部定位。我们感兴趣的是确定脊髓和楔束输入是否构成一个均匀的传入源，以及是否有证据表明它们发挥不同的功能作用。我们还想确定rDAO的躯体定位是否是其传入源点对点投射的结果，或者该投射是否表明橄榄核处传入纤维有重新组织。使用单细胞记录来识别rDAO的特定区域，并通过使用小麦胚凝集素 - 辣根过氧化物酶（WGA - HRP）作为示踪剂来确定已识别区域的输入局部定位。逆行追踪的结果通过使用WGA - HRP作为来自输入源的顺行示踪剂得到证实。向rDAO提供输入的楔束和脊髓神经元构成两个不同的神经群体。一个群体由尾侧楔束核和吻侧两个颈段的VI层中的细胞组成，另一个群体由吻侧楔束核中的细胞组成。尾侧楔束核和吻侧颈段中的细胞是大型多极神经元，它们形成rDAO输入细胞的单列。该细胞列以拓扑方式投射至对侧rDAO，细胞列的吻侧区域投射至吻侧rDAO，其中包含对同侧肩部、躯干和近端前肢的体感刺激作出反应的细胞。细胞列的尾侧区域投射至尾侧rDAO，其中包含对远端前肢刺激作出反应的细胞。尽管存在这种局部定位，但输入列相邻区域的终末存在很大程度的重叠，这表明在rDAO处发生了重大的重新组织。来自吻侧楔束核的投射起源于向双侧投射至rDAO的小神经元，并且来自吻侧楔束核的输入缺乏清晰的局部定位。我们提出，来自细胞列的输入负责rDAO神经元的体感敏感性，而来自吻侧楔束核的输入很可能本质上是调节性的，可能是抑制性的。
