Swanson J J, Kuehl-Kovarik M C, Elmquist J K, Sakaguchi D S, Jacobson C D
Department of Veterinary Anatomy, Iowa State University, Ames, IA 50011, USA.
Brain Res Dev Brain Res. 1999 Feb 5;112(2):159-72. doi: 10.1016/s0165-3806(98)00160-6.
The development of the facial and hypoglossal motor nuclei were examined in the neonatal Brazilian opossum (Monodelphis domestica), a marsupial in which postnatal central nervous system development has been well characterized. In this study, we utilized postnatal injection of the retrograde tracer cholera toxin subunit B (CtB) to characterize the formation of the facial and hypoglossal motor nuclei in the developing neonatal opossum brainstem. Injections of CtB were made into the cheek/lip region or tongue of opossum pups to retrogradely label the facial or hypoglossal motor nuclei, respectively. Following a 2 h survival time, facial motoneurons in newborn opossum pups (1 PN) exhibited CtB labeling, with their cell bodies localized near the developing cranial abducens nucleus. At 3 and 5 PN, following a 48 h survival time, CtB-labeled facial motoneurons were observed in and migrating to the region of the adult facial motor nucleus in the rostral medulla. Between 7 and 10 PN, almost all facial motoneurons had migrated to their destination within the facial motor nucleus. Hypoglossal motoneurons also exhibited CtB labeling from 1 PN; however, their cell bodies were localized within the hypoglossal motor nucleus at the earliest age examined. Double label studies, to examine guidance of facial motoneurons during migration, demonstrated that CtB-labeled facial motoneurons are in close proximity to vimentin-like immunostained radial glial fibers during migration. These results suggest: (1) migration of facial motoneurons to the facial motor nucleus is a postnatal event, (2) efferent projections from facial and hypoglossal motoneurons project into the peripheral region of their target muscles from the day of birth, and (3) facial motoneurons migrate to their destination in the brainstem thereafter, in close association with radial glial fibers.
在新生巴西负鼠（Monodelphis domestica）中研究了面神经核和舌下神经运动核的发育情况，巴西负鼠是一种有袋动物，其出生后中枢神经系统的发育已得到充分表征。在本研究中，我们利用出生后注射逆行示踪剂霍乱毒素B亚单位（CtB）来表征新生负鼠脑干中面神经核和舌下神经运动核的形成。将CtB分别注射到负鼠幼崽的脸颊/唇部区域或舌头，以逆行标记面神经核或舌下神经运动核。在2小时的存活期后，新生负鼠幼崽（出生后1天）的面神经运动神经元显示出CtB标记，其细胞体位于发育中的展神经核附近。在出生后3天和5天，经过48小时的存活期后，在延髓前部观察到CtB标记的面神经运动神经元并向成年面神经核区域迁移。在出生后7天至10天之间，几乎所有面神经运动神经元都已迁移到面神经核内的目的地。舌下神经运动神经元从出生后1天也显示出CtB标记；然而，在最早检查的年龄，它们的细胞体就位于舌下神经运动核内。为了研究面神经运动神经元迁移过程中的导向作用，进行了双重标记研究，结果表明，在迁移过程中，CtB标记的面神经运动神经元与波形蛋白样免疫染色的放射状胶质纤维紧密相邻。这些结果表明：（1）面神经运动神经元向面神经核的迁移是出生后的事件，（2）面神经和舌下神经运动神经元的传出投射从出生之日起就投射到其靶肌肉的周边区域，（3）此后，面神经运动神经元迁移到脑干中的目的地，与放射状胶质纤维密切相关。
