Watson Winsor H, Newcomb James M, Thompson Stuart
Zoology Department and Center for Marine Biology, University of New Hampshire, Durham, New Hampshire 03824, USA.
Biol Bull. 2002 Oct;203(2):152-60. doi: 10.2307/1543384.
The nudibranch Melibe leonina swims by rhythmically bending from side to side at a frequency of 1 cycle every 2-4 s. The objective of this study was to locate putative swim motoneurons (pSMNs) that drive these lateral flexions and determine if swimming in this species is produced by a swim central pattern generator (sCPG). In the first set of experiments, intracellular recordings were obtained from pSMNs in semi-intact, swimming animals. About 10-14 pSMNs were identified on the dorsal surface of each pedal ganglion and 4-7 on the ventral side. In general, the pSMNs in a given pedal ganglion fired synchronously and caused the animal to flex in that direction, whereas the pSMNs in the opposite pedal ganglion fired in anti-phase. When swimming stopped, so did rhythmic pSMN bursting; when swimming commenced, pSMNs resumed bursting. In the second series of experiments, intracellular recordings were obtained from pSMNs in isolated brains that spontaneously expressed the swim motor program. The pattern of activity recorded from pSMNs in isolated brains was very similar to the bursting pattern obtained from the same pSMNs in semi-intact animals, indicating that the sCPG can produce the swim rhythm in the absence of sensory feedback. Exposing the brain to light or cutting the pedal-pedal connectives inhibited fictive swimming in the isolated brain. The pSMNs do not appear to participate in the sCPG. Rather, they received rhythmic excitatory and inhibitory synaptic input from interneurons that probably comprise the sCPG circuit.
海蛞蝓Melibe leonina通过有节奏地左右弯曲来游动，频率为每2 - 4秒一个周期。本研究的目的是定位驱动这些侧向弯曲的假定游泳运动神经元（pSMN），并确定该物种的游泳是否由游泳中央模式发生器（sCPG）产生。在第一组实验中，从半完整的游泳动物的pSMN获得细胞内记录。在每个足神经节的背表面识别出约10 - 14个pSMN，腹侧有4 - 7个。一般来说，给定足神经节中的pSMN同步放电，使动物向该方向弯曲，而相对足神经节中的pSMN则反相放电。当游泳停止时，有节奏的pSMN爆发也停止；当游泳开始时，pSMN恢复爆发。在第二系列实验中，从自发表达游泳运动程序的离体脑的pSMN获得细胞内记录。从离体脑中的pSMN记录到的活动模式与从半完整动物中相同pSMN获得的爆发模式非常相似，表明sCPG在没有感觉反馈的情况下可以产生游泳节律。将脑暴露于光下或切断足 - 足连接会抑制离体脑中的虚构游泳。pSMN似乎不参与sCPG。相反，它们从可能构成sCPG回路的中间神经元接收有节奏的兴奋性和抑制性突触输入。
