Motor output characterizing thanatosis in the cricket Gryllus bimaculatus
Motor output characterizing thanatosis in the cricket Gryllus bimaculatus
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DOI：
10.1242/jeb.01220
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发表时间：
2004-10-01
影响因子：
2.8
通讯作者：
Nishino, H
中科院分区：
文献类型：
--
作者：
Nishino, H
当随意的腿部运动被强制限制时，双斑蟋蟀表现出突然的僵硬不动(死亡)。所有腿部的胫骨关节僵硬地固定几分钟。死亡的典型屈腿姿势是由胫骨屈肌维持的。为了在运动输出水平上描述死亡的特征，我们研究了后胸段胫骨肌的力学和生理特性。副屈肌，特别是在板球中发育良好的，在主屈肌的驱动下，稳定地维持胫骨的屈曲。拴系蟋蟀屈肌的细胞外记录显示，中等兴奋单位和快速兴奋单位的活动几乎完全被抑制，而慢兴奋单位在死亡期间坚持紧张地放电。慢兴奋单位的放电频率随着胫骨的屈曲而逐渐增加，但仍低于静止状态下的放电频率。常见的抑制性运动神经元在静息状态下零星地放电，在昏迷过程中受到抑制，尤其是在开始时，在觉醒后立即表现出强烈的兴奋。这些发现表明，在死亡期间，整个运动神经元池处于主动抑制下，屈肌僵硬是通过缓慢兴奋的微弱放电和抑制物的抑制来维持的。
The cricket Gryllus bimaculatus displays a sudden rigid immobility (thanatosis) when voluntary leg movements are forcibly restrained. The tibial joints in all legs are stiffly immobilized for several minutes. The flexed-leg posture typical of thanatosis is maintained by the flexor tibiae muscle. To characterize thanatosis at the motor output level, the mechanical and physiological properties of the metathoracic tibia muscle were investigated. The accessory flexor muscle, especially well-developed in the cricket, acts to stably maintain the tibial flexion driven by the main flexor muscle. Extracellular recordings from the flexor muscle of tethered crickets revealed that activity of intermediate- and fast-excitatory units was almost completely suppressed, while slow-excitatory units persisted in firing tonically during thanatosis. The firing rate of slow-excitatory units progressively increased as the tibia flexed, but remained less than the firing rate seen in the quiescent state. Common inhibitory motor neurones that fire sporadically in the quiescent state were suppressed during thanatosis, especially in the beginning, and showed a large excitation immediately after arousal. These findings suggest that the entire motor neuronal pool is held under active suppression during thanatosis, and that flexor muscle rigidity is maintained by a weak discharge of the slow exciters together with suppression of the inhibitors.