The Recognition of the Distribution Features of Corticospinal Neurons by a Retrograde Trans-synaptic Tracing to Elucidate the Clinical Application of Contralateral Middle Trunk Transfer

• Published in: Neuroscience 2020-01, Vol.424, p.86-101
• Main Authors: Wang, Fei, Shen, Jun, Jiang, Su, Qiu, Yanqun, Ye, Xuan, Wang, Chengpan, Liang, Chunmin, Xu, Wendong
• Format: Article
• Language: English
• Subjects: Animals; Brachial plexus; Cerebral cortex; Cerebral Cortex - chemistry; Cerebral Cortex - cytology; Cerebral Cortex - physiology; Corticospinal neurons (CSNs); Female; Fluorescent Antibody Technique - methods; Fluorescent Dyes - analysis; Mice; Mice, Inbred C57BL; Neurons - chemistry; Neurons - physiology; Pseudorabies virus (PRV); Pyramidal Tracts - chemistry; Pyramidal Tracts - cytology; Pyramidal Tracts - physiology; Retrograde trans-neuronal tracing; Synapses - chemistry; Synapses - physiology
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2019.09.030

•The CSNs labelled by the upper, middle, and lower trunk were all widely distributed over M1, M2, S1, and S2.•The three trunk-labelled CSNs were intermingled, but not individually clustered in specific subregions in M1, M2, S1, S2.•Most of the CSNs were co-labelled, especially the middle trunk-labelled CSNs with higher proportion of co-labelled cells. Corticospinal neurons (CSNs) undertake direct cortical outputs to the spinal cord and innervate the upper limb through the brachial plexus. Our previous study has shown that the contralateral middle trunk transfer to the paralyzed upper extremity due to cerebral injury can reconstruct the functional cerebral cortex and improve the function of the paralyzed upper extremity. To interpret the cortical reconstruction and the motor improvement after the middle trunk transfer, we explored the distribution of CSNs connecting to the middle, upper, and lower trunk of the brachial plexus by retrograde trans-neuronal tracing using pseudorabies virus (PRV-EGFP or PRV-mRFP). We show that, rather than an individual specific area, these CSNs labelled by each trunk of the brachial plexus were widespread and mainly assembled within the primary motor cortex (M1), secondary motor cortex (M2), primary somatosensory cortex (S1), and slightly within the secondary somatosensory cortex (S2). The three trunk-labelled CSNs were intermingled in these cortices, and mostly connected to more than two trunks, especially the middle trunk-labelled CSNs with higher proportion of co-labelled neurons. Our findings revealed the distribution features of CSNs connecting to the adjacent spinal nerves that innervate the upper limb, which can improve our understanding of the corticospinal circuits associated with motor improvement and the functional cortical reconstruction after the middle trunk transfer.