Neural Regeneration Research ›› 2022, Vol. 17 ›› Issue (1): 228-232.doi: 10.4103/1673-5374.315228

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The anatomical, electrophysiological and histological observations of muscle contraction units in rabbits: a new perspective on nerve injury and regeneration

Ting-Min Xu1, 2, #, Bo Chen2, 3, 4, #, Zong-Xue Jin5, Xiao-Feng Yin1, 2, Pei-Xun Zhang1, 2, Bao-Guo Jiang1, 2, 3, 4, *   

  1. 1Department of Trauma and Orthopedics, Peking University People’s Hospital, Beijing, China; 2Key Laboratory of Trauma and Neural Regeneration (Peking University), Ministry of Education, Beijing, China; 3Trauma Center, Peking University People’s Hospital, Beijing, China; 4National Trauma Medical Center, Beijing, China; 5Department of Rehabilitation, Peking University People’s Hospital, Beijing, China
  • Online:2022-01-05 Published:2021-09-22
  • Contact: Bao-Guo Jiang, MD, jiangbaoguo@vip.sina.com.
  • Supported by:
    This study was supported by Peking University Clinical Scientist Program of China, No. BMU2019LCKXJ005, and the Fundamental Research Funds for the Central Universities, Key Laboratory of Trauma and Neural Regeneration, Ministry of Education of China, No. BMU2019XY007-01 (both to BGJ).

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Abstract: In the conventional view a muscle is composed of intermediate structures before its further division into microscopic muscle fibers. Our experiments in mice have confirmed this intermediate structure is composed of the lamella cluster formed by motor endplates, the innervating nerve branches and the corresponding muscle fibers, which can be viewed as an independent structural and functional unit. In this study, we verified the presence of these muscle construction units in rabbits. The results showed that the muscular branch of the femoral nerve sent out 4–6 nerve branches into the quadriceps and the tibial nerve sent out 4–7 nerve branches into the gastrocnemius. When each nerve branch of the femoral nerve was stimulated from the most lateral to the medial, the contraction of the lateral muscle, intermediate muscle and medial muscle of the quadriceps could be induced by electrically stimulating at least one nerve branch. When stimulating each nerve branch of the tibial nerve from the lateral to the medial, the muscle contraction of the lateral muscle 1, lateral muscle 2, lateral muscle 3 and medial muscle of the gastrocnemius could be induced by electrically stimulating at least one nerve branch. Electrical stimulation of each nerve branch resulted in different electromyographical waves recorded in different muscle subgroups. Hematoxylin-eosin staining showed most of the nerve branches around the neuromuscular junctions consisted of one individual neural tract, a few consisted of two or more neural tracts. The muscles of the lower limb in the rabbit can be subdivided into different muscle subgroups, each innervated by different nerve branches, thereby allowing much more complex muscle activities than traditionally stated. Together, the nerve branches and the innervated muscle subgroups can be viewed as an independent structural and functional unit. This study was approved by the Animal Ethics Committee of Peking University People’s Hospital (approval No. 2019PHE027) on October 20, 2019.

Key words: anatomy, electrophysiology, femoral nerve, hematoxylin-eosin staining, gastrocnemius, motor endplate, muscle contraction unit, peripheral nerve, quadriceps, rabbit, skeletal muscle, tibial nerve