Neural organization of vertical saccadic eye movement

为了解扫视性眼动产生的神经机制，分析了麻醉猫水平眼神经系统从上级丘（SC）到眼运动神经元的神经组织结构，并分析了外展神经核内的内直肌运动神经元、内直肌运动神经元和核间神经元（INNs）对SC刺激的细胞内反应。外展运动神经元通过同侧旁正中脑桥网状结构（PPRF）接受来自对侧SC的双突触兴奋性输入，通过对侧PPRF接受来自同侧SC的双突触抑制性输入。将WGA-HRP注入外展神经后，在对侧PPRF的头、尾侧外展神经核的SC内注射右旋糖酐-生物素，经神经元标记终末运动前神经元，并将标记终末运动前神经元的轴突终末标记于对侧PPRF的头、尾侧外展神经核。这些顶盖网状纤维的轴突终末与终末级运动前神经元直接接触，终末级运动前神经元终止于同侧外展神经元和对侧外展神经元。INNs在展神经核收到来自对侧SC和来自同侧SC的双突触抑制性输入的双突触兴奋性输入。这种模式是相同的，在展神经运动神经元。内直肌运动神经元通过对侧INN接受来自同侧SC的三突触兴奋性输入。将SC的输出传递到PPRF的有两组顶盖网状神经元，一组投射到PPRF，但不投射到脊髓，另一组既投射到PPRF又投射到脊髓。

To understand the neural mechanisms of saccadic eye movement generation, the neural organization from the superior colliculuc (SC) to ocular motoneurons in the horizontal oculomotor system was analyzed in the anesthetized cat. Intracellular responses to stimulation ot the SC were analyzed in abducens motoneurons, medial rectus motoneurons and internuclear neurons (INNs) in the abducens nucleus. Abducens motoneurons received disynaptic excitatory inputs from the contralataeral SC via the ipsilateral paramedian pontine reticular formation (PPRF) and disynaptic inhibitory inputs from the ipsilateral SC via the contralateral PPRF.These electrophysiological findings were confirmed by anatomical experiments. Last-order premotor neurons were labeled transneuronally after injecting WGA-HRP into the abducens nerve, and in the same preparations dextran-biotin injection into the SC labeled axon terminals of tectoreticular neurons orthgradely in the contralateral PPRF rostral and caudal to the abducens nucleus. These axon terminals of tectoreticular fibers made direct contacts with last-order premotor neurons terminating on ipsilateral abducens motoneurons and contralateral abducens motoneurons. INNs in the abducens nucleus received disynaptic excitatory inputs from the contralateral SC and disynaptic inhibitory inputs from the ipsilateral SC.This pattern was the same as in abducens motoneurons. Medial rectus motoneurons received trisynaptic excitatory inputs from the ipsilateral SC via the contralateral INNs. Two groups of tectoreticular neurons were identified to convey output from the SC to the PPRF.One group projected to the PPRF,but not to the spinal cord, and the other group projected to both the PPRF and the spinal cord.