Interneurons between giant axons and motoneurons in crayfish escape circuitry.
Interneurons between giant axons and motoneurons in crayfish escape circuitry.
复制标题
小龙虾逃逸回路中巨型轴突和运动神经元之间的中间神经元。
DOI：
10.1152/jn.1981.45.3.550
复制
发表时间：
1981
影响因子：
2.5
通讯作者：
Wine,JJ
中科院分区：
文献类型：
--
作者：
Kramer,AP;Krasne,FB;Wine,JJ
1.一般认为，小龙虾巨型纤维通过与两类相屈肌运动神经元--运动巨细胞(MOGS)和非巨型快速屈肌运动神经元(FF)--直接联系而产生翻转运动。图中显示，巨人还刺激了一个与Ff建立联系的中间神经元网络。2.该网络包括每个腹部半段内的节内神经元--节段性巨细胞(SG)和许多节间神经元，并对其中两个神经元(I_2和I_3)进行了详细的研究。3.SGS由巨型纤维可靠地驱动，它们反过来又驱动其半节段的FF，与巨型纤维本身一样有效；可能是巨型纤维主要通过SGS来激发FF。SGS还有一个传出的第一根轴突，我们一直无法确定其外周靶点。4.I2和I3分别起源于第二和第三腹神经节，下行至最后一个神经节。在它们起源的神经节中，它们可靠地由巨型纤维和SGS驱动。此外，I2对I3有微弱的兴奋作用，两者都接受来自FF的微弱的、明显直接的兴奋性输入，以及来自未知传入来源的较不直接的兴奋性和抑制性输入。两者都微弱地兴奋起始神经节后面的神经节中的大多数神经纤维。这种激发加上巨型纤维和SGS直接产生的激发，我们相信，有时是导致FF点火的决定性因素。它们的放电也引起抑制，参与抑制再传入的效果，就像巨型纤维本身一样。5.I_3强烈兴奋某些尾扇肌(腹侧和后侧屈肌)的运动神经元。然而，在一些巨大的纤维介导的后空翻中，这些肌肉的收缩将是不适应的。因此，当总是招募I3的巨大纤维放电时，它们会导致运动神经元的抑制，从而使来自I3的兴奋性输入失效。在正式层面上，这意味着被视为命令神经元的巨人不仅驱动，而且还改变或调节它们控制的从属运动模式生成网络。6.众所周知，在没有巨人参与的情况下，没有巨人参与的尾部翻转不会像巨人那样刻板印象。结果表明，巨型纤维与FF之间存在复杂的回路可能与部分回路的使用有关，也与FF本身在非巨型翻转过程中的作用有关。
1. Crayfish giant fibers are generally believed to generate tailflip movements by means of direct connections to two classes of phasic flexor muscle motoneurons, the motor giants (MoGs) and the nongiant fast flexor motoneurons (FFs). It is shown here that the giants also stimulate a network of interneurons that make connections with the FFs. 2. This network includes an intraganglionic neuron, the segmental giant (SG), in each abdominal hemisegment and a number of intersegmental neurons, two of which (I2 and I3) were studied in detail. 3. The SGs are driven reliably by the giant fibers and they in turn drive the FFs of their hemisegment about as effectively as do the giant fibers themselves; it is possible that the giant fibers excite the FFs mainly by way of the SGs. The SGs also have an efferent first root axon whose peripheral targets we have been unable to determine. 4. I2 and I3 originate in the second and third abdominal ganglia, respectively, and descend to the last ganglion. In their ganglia of origin they are reliably driven by the giant fibers and by the SGs. In addition, I2 weakly excites I3 and both receive weak, apparently direct, excitatory input from FFs as well as less direct excitatory and inhibitory input from unidentified afferent sources. Both weakly excite most FFs in ganglia behind the one in which they originate. This excitation adds to that produced directly by giant fibers and SGs and, we believe, is sometimes decisive in causing FF firing. Their firing also causes inhibition involved in suppressing effects of reafference, as do the giant fibers themselves. 5. I3 strongly excites the motoneurons of certain tail fan muscles (the ventral and posterior telson flexors). However, the contraction of these muscles would be maladaptive during some giant fiber-mediated tailflips. Accordingly, when the giant fibers, which always recruit I3, fire, they cause an inhibition of the motoneurons that nullifies the excitatory input from I3. At a formal level this means that the giants, viewed as command neurons, not only drive but also alter or modulate the subordinate motor pattern-generating network that they control. 6. Tailflips that are less stereotyped than those mediated by giant fibers are known to occur without participation of the giants. It is suggested that the presence of complex circuitry mediating between giant fibers and FFs may be related to the use of portions of this circuitry as well as the FFs themselves in production of nongiant tailflips.