Chiba C M, Rankin C H
Department of Psychology, University of British Columbia, Vancouver, Canada.
J Neurobiol. 1990 Jun;21(4):543-54. doi: 10.1002/neu.480210403.
Reversals of forward locomotion in the nematode Caenorhabditis elegans are thought to be mediated by a common neural circuit, the touch withdrawal circuit. Despite substantial neuroanatomical changes over post-embryonic development, one reversal behavior, the head-touch withdrawal reflex, does not appear to change over development (Chalfie and Sulston, 1981). The experiments reported here indicate that two other reversal behaviors, spontaneous reversals and the tap reversal reflex to vibratory stimuli, show developmental changes. Young adult animals showed higher frequencies of spontaneous reversals than all other developmental stages, while larval stages differed from adults in their pattern of responses to tap. Although animals of all stages reversed in response to touch, taps elicited both reversals and accelerations of forward movement. In response to single taps, larval stages reversed on approximately half the occasions; young adult and 4-day-old adults almost always reversed. Increasing stimulus magnitudes increased the probability of accelerations at all developmental stages, but larval stages showed fewer reversals and more accelerations than adults. The behavioral changes observed coincide with known periods of neuroanatomical change in the touch withdrawal circuit. The addition of a late-developing sensory neuron, AVM, is implicated in the behavioral differences between juveniles and adults.
线虫秀丽隐杆线虫向前运动的逆转被认为是由一个共同的神经回路——触觉撤离回路介导的。尽管在胚胎后发育过程中神经解剖结构发生了显著变化，但一种逆转行为——头部触觉撤离反射，在发育过程中似乎没有变化（查尔菲和萨尔斯顿，1981年）。这里报道的实验表明，另外两种逆转行为——自发逆转和对振动刺激的轻拍逆转反射，表现出发育变化。年轻成年动物的自发逆转频率高于所有其他发育阶段，而幼虫阶段在对轻拍的反应模式上与成年动物不同。尽管所有阶段的动物都会因触摸而逆转，但轻拍会引发逆转和向前运动的加速。对于单次轻拍，幼虫阶段大约有一半的情况下会逆转；年轻成年动物和4日龄成年动物几乎总是会逆转。增加刺激强度会增加所有发育阶段加速的概率，但幼虫阶段的逆转次数比成年动物少，加速次数比成年动物多。观察到的行为变化与触觉撤离回路中已知的神经解剖结构变化时期相吻合。一个后期发育的感觉神经元AVM的添加与幼虫和成年动物之间的行为差异有关。
