Jing J, Gillette R
Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana, Illinois 61801, USA.
J Neurophysiol. 1999 Feb;81(2):654-67. doi: 10.1152/jn.1999.81.2.654.
Escape swimming in the notaspid opisthobranch Pleurobranchaea is an episode of alternating dorsal and ventral body flexions that overrides all other behaviors. We have explored the structure of the central pattern generator (CPG) in the cerebropleural ganglion as part of a study of neural network interactions underlying decision making in normal behavior. The CPG comprises at least eight bilaterally paired interneurons, each of which contributes and is phase-locked to the swim rhythm. Dorsal flexion is mediated by hemiganglion ensembles of four serotonin-immunoreactive neurons, the As1, As2, As3, and As4, and an electrically coupled pair, the A1 and A10 cells. When stimulated, A10 commands fictive swimming in the isolated CNS and actual swimming behavior in whole animals. As1-4 provide prolonged, neuromodulatory excitation enhancing dorsal flexion bursts and swim cycle number. Ventral flexion is mediated by the A3 cell and a ventral swim interneuron, IVS, the soma of which is yet unlocated. Initiation of a swim episode begins with persistent firing in A10, followed by recruitment of As1-4 and A1 into dorsal flexion. Recurrent excitation within the As1-4 ensemble and with A1/A10 may reinforce coactivity. Synchrony among swim interneuron partners and bilateral coordination is promoted by electrical coupling among the A1/A10 and As4 pairs, and among unilateral As2-4, and reciprocal chemical excitation between contralateral As1-4 groups. The switch from dorsal to ventral flexion coincides with delayed recruitment of A3, which is coupled electrically to A1, and with recurrent inhibition from A3/IVS to A1/A10. The alternating phase relation may be reinforced by reciprocal inhibition between As1-4 and IVS. Pleurobranchaea's swim resembles that of the nudibranch Tritonia; we find that the CPGs are similar in many details, suggesting that the behavior and network are primitive characters derived from a common pleurobranchid ancestor.
在无楯目后鳃亚纲动物侧鳃海牛中，逃避游泳是一段由背部和腹部交替弯曲组成的过程，它会压倒所有其他行为。作为对正常行为决策背后神经网络相互作用研究的一部分，我们探究了脑胸膜神经节中中央模式发生器（CPG）的结构。CPG至少由八对双侧配对的中间神经元组成，每一个中间神经元都对游泳节律有贡献并与之锁相。背部弯曲由四个5-羟色胺免疫反应性神经元（As1、As2、As3和As4）以及一对电耦合细胞（A1和A10细胞）的半神经节集合介导。受到刺激时，A10在离体中枢神经系统中引发虚拟游泳，并在完整动物中引发实际游泳行为。As1-4提供持续的神经调节性兴奋，增强背部弯曲爆发和游泳周期次数。腹部弯曲由A3细胞和一个腹侧游泳中间神经元IVS介导，IVS的胞体位置尚未确定。游泳过程的启动始于A10的持续放电，随后As1-4和A1被募集到背部弯曲中。As1-4集合内以及与A1/A10之间的反复兴奋可能会加强共同活动。A1/A10和As4对之间、单侧As2-4之间的电耦合，以及对侧As1-4组之间的相互化学兴奋促进了游泳中间神经元伙伴之间的同步和双侧协调。从背部弯曲到腹部弯曲的转换与A3的延迟募集同时发生，A3与A1电耦合，并且伴随着从A3/IVS到A1/A10的反复抑制。As1-4和IVS之间的相互抑制可能会加强交替相位关系。侧鳃海牛的游泳与裸鳃类动物海神鳃海牛相似；我们发现CPG在许多细节上是相似的，这表明这种行为和神经网络是源自共同侧鳃海牛祖先的原始特征。
