VanderHorst V G, Terasawa E, Ralston H J
Department of Anatomy, University of California at San Francisco, 94143-0452, USA.
Neuroscience. 2001;107(1):117-25. doi: 10.1016/s0306-4522(01)00343-8.
Vocalization and straining-related activities require the activation of laryngeal muscles. The control of laryngeal muscles during these activities is thought to be mediated by a pathway from the periaqueductal gray via premotor neurons in the nucleus retroambiguus to laryngeal motoneurons in the nucleus ambiguus. However, direct contacts between the nucleus retroambiguus and laryngeal motoneurons have never been demonstrated anatomically. Moreover, data in primates about the nucleus retroambiguus-nucleus ambiguus pathway are lacking. Therefore, the present study examines the projection from the nucleus retroambiguus region to laryngeal motoneurons in the rhesus monkey at the light and electron microscopic levels. Injections with wheat germ agglutinin-horseradish peroxidase were made into the nucleus retroambiguus in five rhesus monkeys to anterogradely label fibers in the nucleus ambiguus. In two of these animals, the cricothyroid muscle was injected with cholera toxin subunit b to identify the motoneurons that supply it. The results show that the nucleus retroambiguus region most densely projects to the compact formation of the nucleus ambiguus, whereas cricothyroid motoneurons, which surround the compact formation, receive a moderate projection. The projections are bilateral, with a contralateral predominance. Ultrastructurally, anterogradely labeled terminal profiles from the nucleus retroambiguus contact cholera toxin subunit b-labeled dendrites of cricothyroid motoneurons. The terminal profiles contain primarily spherical vesicles and form asymmetrical contacts with cricothyroid motoneurons. This study demonstrates that the nucleus retroambiguus region projects to the nucleus ambiguus in the primate. Some of these projections include monosynaptic connections to laryngeal motoneurons. This pathway is important for the control of the vocal folds during vocalization and straining-related activities.
发声和与用力相关的活动需要喉肌的激活。在这些活动中，喉肌的控制被认为是通过一条从导水管周围灰质经疑核后核的运动前神经元到疑核中的喉运动神经元的通路介导的。然而，疑核后核与喉运动神经元之间的直接联系从未在解剖学上得到证实。此外，灵长类动物中关于疑核后核 - 疑核通路的数据也很缺乏。因此，本研究在光镜和电镜水平上研究了恒河猴疑核后核区域向喉运动神经元的投射。向五只恒河猴的疑核后核注射小麦胚芽凝集素 - 辣根过氧化物酶，以顺行标记疑核中的纤维。在其中两只动物中，向环甲肌注射霍乱毒素亚基b以识别支配它的运动神经元。结果表明，疑核后核区域最密集地投射到疑核的紧密结构，而围绕紧密结构的环甲肌运动神经元接受适度的投射。这些投射是双侧的，以对侧为主。在超微结构上，疑核后核的顺行标记终末轮廓与环甲肌运动神经元的霍乱毒素亚基b标记的树突接触。终末轮廓主要包含球形囊泡，并与环甲肌运动神经元形成不对称接触。本研究表明，疑核后核区域向灵长类动物的疑核投射。其中一些投射包括与喉运动神经元的单突触连接。这条通路对于发声和与用力相关的活动中声带的控制很重要。
