Brodfuehrer P D, Friesen W O
J Neurobiol. 1986 Nov;17(6):697-705. doi: 10.1002/neu.480170612.
We investigated the role played by the cephalic nervous system in the control of swimming activity in the leech, Hirudo medicinalis, by comparing swimming activity in isolated leech nerve cords that included the head ganglia (supra- and subesophageal ganglia) with swimming activity in nerve cords from which these ganglia were removed. We found that the presence of these cephalic ganglia had an inhibitory influence on the reliability with which stimulation of peripheral (DP) nerves and intracellular stimulation of swim-initiating neurons initiated and maintained swimming activity. In addition, swimming activity recorded from both oscillator and motor neurons in preparations that included head ganglia frequently exhibited irregular bursting patterns consisting of missed, weak, or sustained bursts. Removal of the two head ganglia as well as the first segmental ganglion eliminated this irregular activity pattern. We also identified a pair of rhythmically active interneurons, SRN1, in the subesophageal ganglion that, when depolarized, could reset the swimming rhythm. Thus the cephalic ganglia and first segmental ganglion of the leech nerve cord are capable of exerting a tonic inhibitory influence as well as a modulatory effect on swimming activity in the segmental nerve cord.
我们通过比较包含头部神经节（咽下神经节和咽下神经节）的离体水蛭神经索的游泳活动与去除这些神经节的神经索的游泳活动，研究了头部神经系统在水蛭（医用水蛭）游泳活动控制中的作用。我们发现，这些头部神经节的存在对刺激外周（DP）神经和对启动游泳的神经元进行细胞内刺激来启动和维持游泳活动的可靠性具有抑制作用。此外，在包含头部神经节的制剂中，从振荡神经元和运动神经元记录到的游泳活动经常表现出不规则的爆发模式，包括漏发、微弱或持续的爆发。去除两个头部神经节以及第一体节神经节消除了这种不规则的活动模式。我们还在咽下神经节中鉴定出一对有节律活动的中间神经元SRN1，当它们去极化时，可以重置游泳节律。因此，水蛭神经索的头部神经节和第一体节神经节能够对节段神经索中的游泳活动施加强直抑制作用以及调节作用。
