Evinger C, Graf W M, Baker R
Department of Neurobiology and Behavior, SUNY Stony Brook 11794.
J Comp Neurol. 1987 Aug 15;262(3):429-45. doi: 10.1002/cne.902620307.
The distribution of extraocular motoneurons and abducens and oculomotor internuclear neurons was determined in guinea pigs by injecting horseradish peroxidase (HRP) into individual extraocular muscles, the abducens nucleus, the oculomotor nucleus, and the cerebellum. Motoneurons in the oculomotor nucleus innervated the ipsilateral inferior rectus, inferior oblique, medial rectus, and the contralateral superior rectus and levator palpebrae muscles. Most motoneurons of the trochlear nucleus projected to the contralateral superior oblique muscle although a small number innervated the ipsilateral superior oblique. The abducens and accessory abducens nuclei innervated the ipsilateral rectus and retractor bulbi muscles, respectively. The somata of abducens internuclear neurons formed a cap around the lateral and ventral aspects of the abducens nucleus. The axons of these internuclear neurons terminated in the medial rectus subdivision of the contralateral oculomotor nucleus. At least two classes of guinea pig oculomotor internuclear interneurons exist. One group, located primarily ventral to the oculomotor nucleus, innervated the abducens nucleus and surrounding regions. The second group, lying mainly in the dorsal midline area of the oculomotor nucleus, projected to the cerebellum. Intracellular staining with HRP demonstrated similar soma-dendritic organization for oculomotor and trochlear motoneurons of both guinea pigs and rabbits. Dendrites of oculomotor motoneurons radiated symmetrically from the soma to cover approximately one-third of the entire nucleus, and each motoneuron sent at least one dendrite into the central gray overlying the oculomotor nucleus. In both species, a small percentage of oculomotor motoneurons possessed axon collaterals that terminated both within and outside of the nucleus. The dendrites of trochlear motoneurons extended into the medial longitudinal fasciculus and the reticular formation lateral to the nucleus. Our data on the topography of motoneurons and internuclear neurons in the guinea pig and soma-dendritic organization of motoneurons in the guinea pig and rabbit show that these species share common organizational and morphological features. In addition, comparison of these data with those from other mammals reveals that dendritic complexity (number of dendrites per motoneuron) of extraocular motoneurons exhibits a systematic increase with animal size.
通过将辣根过氧化物酶（HRP）注入豚鼠的单个眼外肌、展神经核、动眼神经核和小脑，确定了眼外运动神经元以及展神经和动眼神经核间神经元的分布。动眼神经核中的运动神经元支配同侧下直肌、下斜肌、内直肌以及对侧上直肌和提上睑肌。滑车神经核的大多数运动神经元投射至对侧上斜肌，尽管少数支配同侧上斜肌。展神经核和副展神经核分别支配同侧直肌和眼球退缩肌。展神经核间神经元的胞体在展神经核的外侧和腹侧形成一个帽状结构。这些核间神经元的轴突终止于对侧动眼神经核的内直肌亚核。豚鼠至少存在两类动眼神经核间中间神经元。一组主要位于动眼神经核腹侧，支配展神经核及其周围区域。第二组主要位于动眼神经核的背中线区域，投射至小脑。用HRP进行细胞内染色显示，豚鼠和家兔的动眼神经和滑车神经运动神经元具有相似的胞体-树突组织。动眼神经运动神经元的树突从胞体对称地向外辐射，覆盖整个核的约三分之一，并且每个运动神经元至少有一个树突伸入覆盖动眼神经核的中央灰质。在这两个物种中，一小部分动眼神经运动神经元具有轴突侧支，其在核内和核外均有终末。滑车神经运动神经元的树突延伸至内侧纵束和核外侧的网状结构。我们关于豚鼠运动神经元和核间神经元的拓扑结构以及豚鼠和家兔运动神经元的胞体-树突组织的数据表明，这些物种具有共同的组织和形态特征。此外，将这些数据与其他哺乳动物的数据进行比较发现，眼外运动神经元的树突复杂性（每个运动神经元的树突数量）随动物体型的增大而系统性增加。
