Neural organization of vertical saccadic eye movement

为了解眼球跳动产生的神经机制，对麻醉猫水平眼球运动系统中从上丘(SC)到眼运动神经元的神经组织进行了分析。分析了外展神经核内运动神经元、内直肌运动神经元和核间神经元对刺激SC的反应。外展运动神经元通过对侧桥旁网状结构(PPRF)接受对侧SC的双突触兴奋性输入，通过对侧桥旁网状结构(PPRF)接受同侧SC的双突触抑制输入，这些电生理结果被解剖学实验证实。将WGA-HRP注射到外展神经，并将右旋糖苷-生物素注射到对侧PPRF吻端和尾端至外展神经核的顶盖网状神经元SC标记的轴突终末，进行跨神经标记。这些构造网状纤维的轴突终末与末级运动神经元直接接触，这些神经元终止于同侧外展运动神经元和对侧外展运动神经元。外展神经核内的INN接受来自对侧SC的双突触兴奋性传入和来自同侧SC的双突触抑制传入，这种模式与外展运动神经元相同。内侧直肌运动神经元通过对侧丘脑束接受同侧SC的三突触兴奋性传入。发现了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.