Arbas E A, Weidner M H
Division of Neurobiology, Arizona Research Laboratories, University of Arizona, Tucson 85721.
J Neurobiol. 1991 Jul;22(5):536-46. doi: 10.1002/neu.480220509.
Autotomy is a process in grasshoppers whereby one or both hindlimbs can be shed to escape a predator or can be abandoned if damaged. It occurs between the trochanter and the femur (second and third leg segments) and once lost, the legs never regenerate. Autotomy severs branches of the leg nerve (N5) but damages no muscles since none span the autotomy plane. We find, however, that undamaged muscles intrinsic to the thorax of grasshoppers, Barytettix psolus, atrophy to less than 15% of their normal mass after autotomy of a hindlimb. These muscles operate the coxa and trochanter (first and second leg segments) and are innervated by branches of nerves 3 and 4; nerve branches that are not damaged by autotomy. Atrophy is localized to the side and body segment where autotomy occurs. Atrophy is evident 7-10 days after loss of a limb, is complete by about 30 days, and follows a similar time course whether induced in young adult, or sexually mature grasshoppers. During autotomy, leg nerve 5 is served distal to the trochanter, the thoracic muscles lose their normal static and dynamic load, and these muscles are subsequently no longer used to support the weight of the insect during posture and locomotion. Experimental loading and unloading of the affected muscles, and cutting of nerves indicated that it is the severing of leg nerve 5 during autotomy that transneuronally induces muscle atrophy.
自残是蝗虫体内的一种过程，在此过程中，蝗虫可自行脱落一条或两条后肢以逃避捕食者，或者在肢体受损时将其舍弃。自残发生在转节和股骨之间（腿部的第二和第三节段），一旦肢体脱落，就不会再生。自残会切断腿部神经（N5）的分支，但不会损伤任何肌肉，因为没有肌肉跨越自残平面。然而，我们发现，在蝗虫Barytettix psolus后肢自残后，其胸部固有的未受损肌肉会萎缩至正常质量的不到15%。这些肌肉控制基节和转节（腿部的第一和第二节段），并由神经3和神经4的分支支配；这些神经分支不会因自残而受损。萎缩局限于自残发生的一侧和身体节段。肢体缺失7至10天后萎缩明显，约30天时完全萎缩，无论在年轻成虫还是性成熟的蝗虫中诱发，萎缩过程都相似。在自残过程中，腿部神经5在转节远端被切断，胸部肌肉失去了正常的静态和动态负荷，随后这些肌肉在姿势和运动过程中不再用于支撑昆虫的体重。对受影响肌肉进行实验性加载和卸载以及切断神经表明，自残过程中腿部神经5的切断会经神经元诱导肌肉萎缩。
