Johnston Rebecca M, Levine Richard B
Department of Neurobiology, University of Arizona, Tucson AZ 85721-0077, USA.
Invert Neurosci. 2002 Oct;4(4):175-92. doi: 10.1007/s10158-002-0019-4. Epub 2002 Aug 3.
In the hawkmoth, Manduca sexta, thoracic leg motoneurons survive the degeneration of the larval leg muscles to innervate new muscles of the adult legs. The same motoneurons, therefore, participate in the very different modes of terrestrial locomotion that are used by larvae (crawling) and adults (walking). Consequently, changes in locomotor behavior may reflect changes in both the CNS and periphery. The present study was undertaken to determine whether motor patterns produced by the isolated CNS of adult Manduca, in the absence of sensory feedback, would resemble adult specific patterns of coordination. Pilocarpine, which evokes a fictive crawling motor pattern from the isolated larval CNS, also evoked robust patterned activity from leg motoneurons in the isolated adult CNS. As in the larva, levator and depressor motoneurons innervating the same leg were active in antiphase. Unlike fictive crawling, however, bursts of activity in levator or depressor motoneurons of one leg alternated with bursts in the homologous motoneurons innervating the opposite leg of the same segment and the leg on the same side in the adjacent segment. The most common mode of intersegmental activity generated by the isolated adult CNS resembled an alternating tripod gait, which is displayed, albeit infrequently, during walking in intact adult Manduca. A detailed analysis revealed specific differences between the patterned motor activity that is evoked from the isolated adult CNS and activity patterns observed during walking in intact animals, perhaps indicating an important role for sensory feedback. Nevertheless, the basic similarity to adult walking and clear distinctions from the larval fictive crawling pattern suggest that changes within the CNS contribute to alterations in locomotor activity during metamorphosis.
在烟草天蛾（Manduca sexta）中，胸部腿部运动神经元在幼虫腿部肌肉退化后存活下来，以支配成虫腿部的新肌肉。因此，相同的运动神经元参与了幼虫（爬行）和成虫（行走）所使用的截然不同的陆地运动模式。因此，运动行为的变化可能反映了中枢神经系统（CNS）和外周的变化。本研究旨在确定在没有感觉反馈的情况下，成年烟草天蛾分离的中枢神经系统产生的运动模式是否类似于成虫特定的协调模式。毛果芸香碱能从分离的幼虫中枢神经系统诱发一种虚构的爬行运动模式，它也能从分离的成年中枢神经系统的腿部运动神经元诱发强烈的模式化活动。与幼虫一样，支配同一条腿的提肌和降肌运动神经元以反相活动。然而，与虚构的爬行不同，一条腿的提肌或降肌运动神经元的活动爆发与支配同一节段相对腿和相邻节段同侧腿的同源运动神经元的活动爆发交替出现。分离的成年中枢神经系统产生的最常见的节间活动模式类似于交替三脚架步态，在完整的成年烟草天蛾行走时偶尔会出现这种步态。详细分析揭示了从分离的成年中枢神经系统诱发的模式化运动活动与在完整动物行走时观察到的活动模式之间的具体差异，这可能表明感觉反馈起着重要作用。尽管如此，与成年行走的基本相似性以及与幼虫虚构爬行模式的明显区别表明，中枢神经系统内的变化有助于变态过程中运动活动的改变。
