Rose P K, Wainwright K, Neuber-Hess M
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
J Comp Neurol. 1992 Jul 8;321(2):312-24. doi: 10.1002/cne.903210210.
The projections of neurons in the lateral vestibular nucleus (LVN) to the upper cervical spinal cord of the cat were investigated by means of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). At the junction of C1 and C2, axons were distributed bilaterally in the ventromedial funiculi, and ipsilaterally in the ventrolateral and lateral funiculi. The majority of boutons were found ipsilateral to the injection sites and most of these boutons were found at the base of the ventral horn and throughout the medial two-thirds of lamina VIII. A more modest termination zone was found along the ventral border of lamina VII and a small number of boutons were scattered in the dorsal horn. Contralateral termination zones were similar to the ipsilateral projections. There were significant changes in the distribution of vestibulospinal axons and density of boutons at the junction of C3 and C4. At this level, most vestibulospinal axons travelled ipsilaterally and were found along the medial border of the ventromedial funiculus and the ventral margin of the ventrolateral funiculus. The overall distribution of boutons near the border of C3 and C4 was similar to the pattern seen at the junction of C1 and C2. However, bouton density fell by a factor of three. Large zones of the grey matter were devoid of boutons in individual experiments. These results demonstrate that the projections of neurons in the LVN to the upper cervical spinal cord are densest in the regions containing motoneurons supplying suboccipital muscles. This result suggests that monosynaptic connections to those motoneurons may be an important part of the neural circuitry responsible for vestibulocollic reflexes. However, the large number of boutons found in regions dorsal to motoneuron nuclei in all upper cervical segments indicates that the primary path from vestibulospinal axons to neck motoneurons may be indirect and involve relays via spinal interneurons.
运用顺行示踪剂菜豆白细胞凝集素（PHA-L），研究了猫外侧前庭核（LVN）神经元向上颈脊髓的投射。在C1和C2交界处，轴突双侧分布于腹内侧索，同侧分布于腹外侧索和外侧索。大多数终扣位于注射部位的同侧，其中大部分终扣位于腹角底部以及整个VIII层内侧三分之二区域。在VII层腹侧边界沿线发现了一个较小的终末区，少量终扣散在于背角。对侧终末区与同侧投射相似。在C3和C4交界处，前庭脊髓轴突的分布和终扣密度有显著变化。在此水平，大多数前庭脊髓轴突同侧走行，位于腹内侧索内侧边界和腹外侧索腹侧边缘沿线。C3和C4边界附近终扣的总体分布与C1和C2交界处所见模式相似。然而，终扣密度下降了三分之一。在个别实验中，灰质的大片区域没有终扣。这些结果表明，LVN神经元向上颈脊髓的投射在含有支配枕下肌运动神经元的区域最为密集。这一结果表明，与那些运动神经元的单突触连接可能是负责前庭颈反射的神经回路的重要组成部分。然而，在所有上颈段运动神经元核背侧区域发现的大量终扣表明，前庭脊髓轴突至颈运动神经元的主要通路可能是间接的，且涉及通过脊髓中间神经元的中继。
