Crawling motor patterns induced by pilocarpine in isolated larval nerve cords of Manduca sexta
Crawling motor patterns induced by pilocarpine in isolated larval nerve cords of Manduca sexta
复制标题
DOI：
10.1152/jn.1996.76.5.3178
复制
发表时间：
1996-11-01
影响因子：
2.5
通讯作者：
Levine, RB
中科院分区：
文献类型：
--
作者：
Johnston, RM;Levine, RB
1.幼虫爬行是一种两侧对称的行为，涉及体壁肌肉中运动活动的前向运动波，以及腹部前腿和胸部腿的顺序运动。本研究的目的是确定是否幼虫中枢神经系统本身，没有阶段性的感觉反馈能够产生与爬行相关的模式化活动。为了确定神经索的输出和爬行之间的相似程度，将神经索产生的运动活动与自由爬行的幼虫的运动活动进行比较.当暴露于毒蕈碱受体激动剂毛果芸香碱（1.0 mM）时，分离的幼虫神经索在供应胸腿、腹部体壁和腹前腿肌肉的运动神经元中产生持久的节律活动。毛果芸香碱引起的节律性活动被毒蕈碱受体拮抗剂阿托品（0.01 mM）和毛果芸香碱（1.0 mM）联合应用可逆地完全消除，表明这种反应是由毒蕈碱样乙酰胆碱受体介导的.与完整动物的爬行相似，孤立神经索中的诱发活动涉及从最后腹段到最前胸段的双侧对称运动活动。胸腿、腹前腿和腹部体壁运动神经元的节律活动表现出节段内和节段间的周期与周期耦合。离体神经索节律活动的平均周期比完整幼虫爬行的周期慢2.5倍，但变化不大。像爬行在完整的动物，在孤立的神经索，爆发活动的背体壁运动神经元发生前腹侧/侧体壁运动神经元内的腹段的活动。从腿前神经记录的诱发爆发活动叠加在高水平的强直活动上。在孤立的神经索，爆发的活动在胸腿提/伸肌运动神经元交替的爆发的活动在降压/屈肌运动神经元。提/伸肌活动的爆发持续时间很短，并且随着周期的增加而保持相对稳定。降压/屈肌活动的爆发持续时间占平均周期的大部分，并随着周期的增加而增加。在整个周期内，提/伸肌运动神经活动和降/屈肌运动神经活动的相位保持相对稳定。在离体神经索中，胸腿运动神经元活动的时间和模式在数量上类似于自由爬行幼虫的胸腿运动活动。由一个孤立的幼虫神经索产生的有节奏的运动活动类似于一个缓慢的版本正常爬行在完整的幼虫。由于在爬行过程中，在分离的神经索中诱导的活动与胸段和腹段的肌肉活动和运动之间有许多相似之处，我们得出结论，中枢机制可以建立爬行运动模式的时间和模式，爬行可以反映中枢模式生成网络的输出。
1. Larval crawling is a bilaterally symmetrical behavior that involves an anterior moving wave of motor activity in the body wall muscles in conjunction with sequential movements of the abdominal prolegs and thoracic legs. The purpose of this study was to determine whether the larval CNS by itself and without phasic sensory feedback was capable of producing patterned activity associated with crawling. To establish the extent of similarity between the output of the isolated nerve cord and crawling, the motor activity produced in isolated larval nerve cords was compared with the motor activity from freely crawling larvae.2. When exposed to the muscarinic receptor agonist pilocarpine (1.0 mM), isolated larval nerve cords produced long-lasting rhythmic activity in the motor neurons that supply the thoracic leg, abdominal body wall, and abdominal proleg muscles. The rhythmic activity evoked by pilocarpine was abolished reversibly and completely by bath application of the muscarinic-receptor antagonist atropine (0.01 mM) in conjunction with pilocarpine (1.0 mM), suggesting that the response was mediated by muscarinic-like acetylcholine receptors.3. Similar to crawling in intact animals, the evoked activity in isolated nerve cords involved bilaterally symmetrical motor activity that progressed from the most posterior abdominal segment to the most anterior thoracic segment. The rhythmic activity in thoracic leg, abdominal proleg, and abdominal body wall motor neurons showed intrasegmental and intersegmental cycle-to-cycle coupling. The average cycle period for rhythmic activity in the isolated nerve cord was similar to 2.5 times slower than the cycle period for crawling in intact larvae, but not more variable.4. Like crawling in intact animals, in isolated nerve cords, bursting activity in the dorsal body wall motor neurons occurred before activity in ventral/lateral body wall motor neurons within an abdominal segment. The evoked bursting activity recorded from the proleg nerve was superimposed on a high level of tonic activity.5. In isolated nerve cords, bursts of activity in the thoracic leg levator/extensor motor neurons alternated with bursts of activity in the depressor/flexor motor neurons. The burst duration of the levator/extensor activity was brief and remained relatively steady as cycle period increased. The burst duration of the depressor/flexor activity occupied the majority of an average cycle and increased as cycle period increased. The phase of both levator/extensor motor nerve activity and depressor/flexor motor nerve activity remained relatively stable over the entire range of cycle periods. The timing and patterning of thoracic leg motor neuron activity in isolated nerve cords quantitatively resembled thoracic leg motor activity in freely crawling larvae.6. The rhythmic motor activity generated by an isolated larval nerve cord resembled a slower version of normal crawling in intact larvae. Because of the many similarities between activity induced in the isolated nerve cord and the muscle activity and movements of thoracic and abdominal segments during crawling, we concluded that central mechanisms can establish the timing and patterning of the crawling motor pattern and that crawling may reflect the output of a central pattern generating network.