Shinoda Y, Ohgaki T, Sugiuchi Y, Futami T
Department of Physiology, School of Medicine, Tokyo Medical and Dental University, Japan.
J Comp Neurol. 1992 Feb 8;316(2):151-72. doi: 10.1002/cne.903160203.
The morphology of single medial vestibulospinal tract (MVST) axons was investigated by iontophoretic injection of horseradish peroxidase into single axons at the upper cervical cord in pentobarbital-anesthetized cats. MVST axons were identified by their monosynaptic responses to stimulation of the vestibular nerve and their direct responses to stimulation of the medial longitudinal fusciculus (MLF). Reconstructions of the axonal trajectory were made from 22 uncrossed and 19 crossed MVST axons at C1-C4. MVST axons ran in the ventral funiculus and gave rise to multiple axon collaterals to the upper cervical gray matter at different segments. These axons could be traced over the distance of 2.5-15.3 mm. Within these lengths, up to 9 axon collaterals were identified per axon (mean +/- s.d., 3.3 +/- 2.0, n = 41). Axon collaterals ramified in the gray matter several times and spread in a delta-like manner in both the transverse and horizontal planes. There were usually gaps free from terminal arborizations between adjacent axon collaterals, since the rostrocaudal extension of individual axon collaterals (mean = 820 microns) was very much limited in contrast to wide intercollateral intervals (mean = 1,510 microns). Axon terminals were distributed mainly in laminae IX, VIII, and VII, and sometimes in laminae VI-IV. Most abundant terminals were observed in lamina IX, including the ventromedial (VM), the spinal accessory (SA) nuclei and the nucleus dorsomedial to the VM nucleus (DM nucleus). A majority of individual axon collaterals provided some terminal branches to at least one of the above three motor nuclei. Axon collaterals projecting to laminae VIII-VI without terminals in the motor nuclei were rarely observed. Individual MVST axons had a preferential terminal distribution in each motor nucleus, but all three motor nuclei were covered by axon terminals of an ensemble of all MVST axons, indicating that all neck muscles innervated by these three motor nuclei are influenced by vestibular inputs through MVST axons. Most collaterals from a single axon produced circumscribed terminal arborizations in one or two common areas in the transverse plane (mainly in lamina IX) that were in line with one another in the longitudinal axis of the cord. This longitudinal arrangement of discontinuous terminal arborizations in lamina IX from a single axon may correspond to a continuous sagittal column of motoneurons for a particular muscle.(ABSTRACT TRUNCATED AT 400 WORDS)
在戊巴比妥麻醉的猫的上颈髓，通过离子电泳法将辣根过氧化物酶注入单根内侧前庭脊髓束（MVST）轴突，研究其形态。通过对前庭神经刺激的单突触反应以及对内侧纵束（MLF）刺激的直接反应来识别MVST轴突。在C1 - C4水平对22根未交叉和19根交叉的MVST轴突进行了轴突轨迹重建。MVST轴突走行于腹侧索，并在不同节段向上颈灰质发出多个轴突侧支。这些轴突可追踪2.5 - 15.3毫米的距离。在这些长度范围内，每根轴突可识别多达9个轴突侧支（平均值±标准差，3.3±2.0，n = 41）。轴突侧支在灰质中多次分支，并在横平面和水平平面呈三角形分布。相邻轴突侧支之间通常存在无终末分支的间隙，因为单个轴突侧支的前后延伸（平均值 = 820微米）与侧支间的宽间距（平均值 = 1510微米）相比非常有限。轴突终末主要分布在板层IX、VIII和VII，有时也分布在板层VI - IV。在板层IX观察到的终末最多，包括腹内侧（VM）、脊髓副核（SA）以及VM核背内侧的核（DM核）。大多数单个轴突侧支至少为上述三个运动核中的一个提供一些终末分支。很少观察到轴突侧支投射到板层VIII - VI而在运动核中无终末。单个MVST轴突在每个运动核中有优先的终末分布，但所有三个运动核都被所有MVST轴突的终末所覆盖，这表明由这三个运动核支配的所有颈部肌肉都受到通过MVST轴突的前庭输入的影响。来自单根轴突的大多数侧支在横平面的一个或两个共同区域（主要在板层IX）产生局限的终末分支，这些分支在脊髓的纵轴上彼此对齐。单个轴突在板层IX中这种不连续终末分支的纵向排列可能对应于特定肌肉的运动神经元的连续矢状柱。（摘要截断于400字）
