Porter J D, Burns L A, May P J
Department of Anatomy, University of Mississippi Medical Center, Jackson 39216.
J Comp Neurol. 1989 Sep 1;287(1):64-81. doi: 10.1002/cne.902870106.
The levator palpebrae superioris and orbicularis oculi are antagonistic muscles that function during movements of the eyelid. The levator also functions in conjunction with superior and inferior rectus muscles in coordinated eye/lid movements. The present study examined the innervation and morphology of these muscles in Cynomolgous monkeys (Macaca fascicularis) in order to provide a better understanding of the anatomical substrate for lid movements. Motoneurons innervating the levator and orbicularis muscles were identified and localized by retrograde transport of WGA/HRP and HRP. Retrogradely labelled levator motoneurons were distributed bilaterally throughout the caudal central division of the oculomotor nucleus. A few labelled cells were also present within the contralateral superior rectus division, possibly because of the spread of tracer at the injection site. The possibility that individual motoneurons collateralize to innervate the levator muscle bilaterally was tested by using double retrograde labelling techniques. Doubly labelled levator motoneurons could not be detected by using a combination of tracers (HRP and Fast Blue). Motoneurons innervating the upper lid portion of the orbicularis oculi muscle were distributed within the dorsal subdivision of the ipsilateral facial motor nucleus, with a few neurons in the corresponding locus of the contralateral facial nucleus. Species differences in levator motoneuron distribution, particularly distinctions in lateral-eyed versus frontal-eyed mammals, are discussed in relation to the neural control of lid movements. The levator palpebrae superioris contains three of the same ultrastructurally defined types of singly innervated muscle fiber found in the global layer of other extraocular muscles and an additional, unique slow-twitch fiber type. Moreover, the multiply innervated fiber types so characteristic of the other extraocular muscles are conspicuously absent from levator muscles. Unlike the rectus and oblique extraocular muscles, the levator lacks a layered distribution of fiber types. The morphological profiles of levator muscle fiber types are such that they generally do not respect traditional fiber classification schemes, but are consistent with a role for the levator in sustained elevation of the lid. The orbicularis oculi muscle, by contrast, exhibited three distinct fiber types that resembled categories of skeletal muscle twitch fibers. One slow-twitch and two fast-twitch fiber types were noted. On the basis of oxidative enzyme profiles and mitochondrial content, the majority of orbicularis oculi fibers would be fatigue-prone, an assessment consistent with their rapid onset/offset of acti
提上睑肌和眼轮匝肌是在眼睑运动时发挥作用的拮抗肌。提上睑肌还在眼球与眼睑的协调运动中与上直肌和下直肌协同发挥作用。本研究对食蟹猴（猕猴）的这些肌肉的神经支配和形态进行了研究，以便更好地了解眼睑运动的解剖学基础。通过WGA/HRP和HRP的逆行运输来识别和定位支配提上睑肌和眼轮匝肌的运动神经元。逆行标记的提上睑肌运动神经元双侧分布于动眼神经核尾侧中央部。对侧上直肌部也有少数标记细胞，这可能是由于注射部位示踪剂的扩散所致。通过使用双重逆行标记技术来检验单个运动神经元是否通过侧支双侧支配提上睑肌的可能性。使用示踪剂组合（HRP和快蓝）未检测到双重标记的提上睑肌运动神经元。支配眼轮匝肌上睑部分的运动神经元分布于同侧面神经运动核的背侧亚核内，对侧面神经核相应部位也有少数神经元。结合眼睑运动的神经控制，讨论了提上睑肌运动神经元分布的种间差异，特别是侧视与正视哺乳动物之间的差异。提上睑肌包含在其他眼外肌整体层中发现的三种相同的超微结构定义的单神经支配肌纤维类型，以及一种额外的、独特的慢肌纤维类型。此外，提上睑肌明显缺乏其他眼外肌特有的多神经支配纤维类型。与直肌和斜肌眼外肌不同，提上睑肌缺乏纤维类型的分层分布。提上睑肌纤维类型的形态特征使得它们通常不符合传统的纤维分类方案，但与提上睑肌在持续提升眼睑中的作用一致。相比之下，眼轮匝肌表现出三种不同的纤维类型，类似于骨骼肌快肌纤维的类别。记录到一种慢肌纤维类型和两种快肌纤维类型。根据氧化酶谱和线粒体含量，眼轮匝肌的大多数纤维容易疲劳，这一评估与它们快速开始/停止活动一致。
