INITIATION OF SWIMMING ACTIVITY BY TRIGGER NEURONS IN THE LEECH SUBESOPHAGEAL GANGLION .3. SENSORY INPUTS TO TR1 AND TR2
INITIATION OF SWIMMING ACTIVITY BY TRIGGER NEURONS IN THE LEECH SUBESOPHAGEAL GANGLION .3. SENSORY INPUTS TO TR1 AND TR2
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DOI：
10.1007/bf00604171
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发表时间：
1986-01-01
影响因子：
2.1
通讯作者：
FRIESEN, WO
中科院分区：
文献类型：
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作者：
BRODFUEHRER, PD;FRIESEN, WO
在本系列的第一篇和第二篇论文中，我们描述了水蛭食道下神经节中的两对中间神经元Tr1和Tr2，它们可以触发孤立中枢神经系统（CNS）的游泳活动。在本文中，我们描述了从先前确定的机械感觉神经元到这些触发神经元的感觉输入。我们发现：1。在孤立的中枢神经系统中，连接到节段神经节的体壁瓣的弱机械刺激（抚摸）会轻微刺激对侧Tr1。强烈的机械刺激（挤压）中侧壁皮瓣引起对侧Tr1的脉冲爆发。两种刺激方式对同侧Tr1和Tr2细胞对的影响要弱得多。2. 在另一个孤立的中枢神经系统中，抚摸附着在头神经节（食管上神经节和食管下神经节）上的体壁瓣会刺激Tr1s和Tr2s，尽管对Tr2s的作用较弱。捏紧会强烈刺激两侧的触发神经元。3. 食管下神经节和第一节段神经节中的压力和伤害性机械感觉神经元（P和N细胞）似乎与对侧Tr1和Tr2形成直接兴奋性突触。机械感觉与同侧触发神经元的相互作用似乎是间接的。4. 超极化导致Tr1功能失活，无论是体壁瓣的弱机械刺激还是P细胞的细胞内刺激，都不会阻止游泳的开始。5. 我们得出的结论是，触发神经元Tr1和Tr2提供了一个兴奋的途径，机械感觉刺激可以启动水蛭游泳活动。这种途径对于强机械刺激似乎比弱机械刺激更重要。由于某些形式的刺激并不需要Tr1对的活性来启动游泳，因此从机械感觉神经元到振荡器网络的其他途径仍未被发现。
In papers I and II of this series, we described two pairs of interneurons, Tr1 and Tr2, in the leech subesophageal ganglion which can trigger swimming activity in the isolated central nervous system (CNS). In this paper, we describe sensory inputs to these trigger neurons from previously identified mechanosensory neurons. We found that: 1. Weak mechanical stimulation (stroking) of a body wall flap attached to a segmental ganglion in an otherwise isolated CNS excites the contralateral Tr1 slightly. Strong mechanical stimulation (pinching) of a mid-body wall flap evokes a burst of impulses in the contralateral Tr1. For both means of stimulation the effects on the ipsilateral Tr1 and Tr2 cell pair were much weaker. 2. Stroking a body wall flap attached to the head ganglion (supra- and subesophageal ganglia) in an otherwise isolated CNS excites both Tr1s and both Tr2s, although the effect is weaker for the Tr2s. Pinching strongly excites both trigger neurons bilaterally. 3. Pressure and nociceptive mechanosensory neurons (P and N cells) in the subesophageal ganglion and the first segmental ganglion appear to make direct excitatory synapses with the contralateral Tr1 and Tr2. Mechanosensory interactions with the ipsilateral trigger neurons appear to be indirect. 4. Functional inactivation of Tr1 by hyperpolarization does not prevent swim initiation either by weak mechanical stimulation of a body-wall flap or by intracellular stimulation of P cells. 5. We conclude that the trigger neurons, Tr1 and Tr2, provide an excitatory pathway by which mechanosensory stimulation can initiate leech swimming activity. This pathway appears more important for strong than for weak mechanical stimulation. Since activity in the Tr1 pair is not required for swim initiation by some forms of stimulation, additional pathways leading from mechanosensory neurons to the oscillator network remain undiscovered.