脊髓呼吸膈运动神经元的形态学特征研究

Morphological characterization of spinal respiratory phrenic motoneurons

目的研究脊髓呼吸相关的膈运动神经元的空间分布位置并比较其与三角肌运动神经元和肋间运动神经元的分布特点差异。方法采用从外周到中枢的逆行示踪研究策略,在成年小鼠(n=3)同侧膈肌、三角肌、肋间肌微量注射霍乱毒素β亚基(cholera toxinβ-subunit,CTB)或伪狂犬病毒(pseudorabies virus,PRV),逆行标记支配目标肌肉的脊髓运动神经元,并进一步分析、比较不同脊髓运动神经元的分布特征。结果CTB和PRV介导的逆行示踪结果显示:成年小鼠膈运动神经元分布在颈髓C3~C6节段前角Ph9区域,且上述两种逆行示踪剂标记膈运动神经元的效率差异无统计学意义。与C5~C6节段的非呼吸相关的三角肌运动胆碱能神经元相比,膈运动神经元分布在同一脊髓节段前角更腹内侧的位置。与胸髓呼吸相关的肋间运动神经元相比,两组神经元分别在颈髓和胸髓中均沿头-尾轴呈束状纵柱形分布,但膈运动神经元在C3~C6节段细胞数量分布相对均一,而肋间运动神经元在T1~T11节段神经元数目变异较大(P<0.0001)。此外,膈运动神经元分布沿头-尾轴逐渐向脊髓前角内侧偏移,而呼吸肋间运动神经元则比较均一地分布在脊髓前角外侧区。结论成年小鼠膈运动神经元分布在颈髓的C3~C6节段前角Ph9区域,位于三角肌运动神经元腹内侧,且其分布模式较胸髓肋间运动神经元更为均一。

Objective To study the spatial distribution of respiratory-related phrenic motoneurons within the spinal cord and comparison of their distribution characteristics with those of deltoid motoneurons and intercostal motoneurons.Methods Using a retrograde tracing strategy from peripheral to central,cholera toxinβ-subunit(CTB)or pseudorabies virus(PRV)was microinjected into the ipsilateral diaphragm,deltoid and intercostal muscles of adult mice(n=3)to retrogradely label the spinal motoneurons innervating the target muscles.Then the distribution characteristics of different spinal motoneurons were analyzed and compared.Results The results of CTB-and PRV-mediated retrograde tracing showed that phrenic motoneurons in adult mice were distributed in the Ph9 region in the anterior horn of the C3~C6 segments of the cervical cord,and there was no significant difference in the efficiency of labeling phrenic motoneurons with either retrograde tracer.The phrenic motoneurons were distributed in a more ventral medial location in the anterior horn of the same spinal cord segment compared to the non-respiratory related deltoid motor cholinergic neurons in the C5~C6 segments.In contrast to respiratory-related intercostal motoneurons in the thoracic cord,both sets of neurons were distributed in a longitudinal column along the rostro-caudal axis in the cervical and thoracic cord,respectively.However,phrenic motoneurons were relatively uniformly distributed in the number of cells in segments C3~C6,whereas intercostal motoneurons were more variable in the number of neurons in segments T1~T11(P<0.0001).In addition,the distribution of phrenic motoneurons was gradually shifted towards the medial anterior horn of the spinal cord along the rostro-caudal axis,whereas respiratory intercostal motoneurons were more uniformly distributed in the lateral anterior horn of the spinal cord.Conclusion Phrenic motoneurons in adult mice are distributed in segments C3~C6 of the cervical cord,which are located in the more medial Ph9 region of the anterior horn as compared to non-respiratory related deltoid motoneurons in the cervical cord,and have a more even distribution pattern than respiratory intercostal motoneurons in the thoracic cord.