Stein Wolfgang, DeLong Nicholas D, Wood Debra E, Nusbaum Michael P
Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Eur J Neurosci. 2007 Sep;26(5):1148-65. doi: 10.1111/j.1460-9568.2007.05744.x.
Co-transmission is a common means of neuronal communication, but its consequences for neuronal signaling within a defined neuronal circuit remain unknown in most systems. We are addressing this issue in the crab stomatogastric nervous system by characterizing how the identified modulatory commissural neuron (MCN)1 uses its co-transmitters to activate the gastric mill (chewing) rhythm in the stomatogastric ganglion (STG). MCN1 contains gamma-aminobutyric acid (GABA) plus the peptides proctolin and Cancer borealis tachykinin-related peptide Ia (CabTRP Ia), which it co-releases during the retractor phase of the gastric mill rhythm to influence both retractor and protractor neurons. By focally applying each MCN1 co-transmitter and pharmacologically manipulating each co-transmitter action during MCN1 stimulation, we found that MCN1 has divergent co-transmitter actions on the gastric mill central pattern generator (CPG), which includes the neurons lateral gastric (LG) and interneuron 1 (Int1), plus the STG terminals of MCN1 (MCN1(STG)). MCN1 used only CabTRP Ia to influence LG, while it used only GABA to influence Int1 and the contralateral MCN1(STG). These MCN1 actions caused a slow excitation of LG, a fast excitation of Int1 and a fast inhibition of MCN1(STG). MCN1-released proctolin had no direct influence on the gastric mill CPG, although it likely indirectly regulates this CPG via its influence on the pyloric rhythm. MCN1 appeared to have no ionotropic actions on the gastric mill follower motor neurons, but it did use proctolin and/or CabTRP Ia to excite them. Thus, a modulatory projection neuron can elicit rhythmic motor activity by using distinct co-transmitters, with different time courses of action, to simultaneously influence different CPG neurons.
共同传递是神经元通讯的一种常见方式，但在大多数系统中，其在特定神经元回路内对神经元信号传导的影响仍不清楚。我们正在通过研究已确定的调节性联合神经元（MCN）1如何利用其共同递质来激活胃神经节（STG）中的胃磨（咀嚼）节律，来解决螃蟹口胃神经系统中的这一问题。MCN1含有γ-氨基丁酸（GABA）以及肽促肠肌肽和北方蟹速激肽相关肽Ia（CabTRP Ia），它在胃磨节律的收缩期共同释放这些物质，以影响收缩神经元和伸展神经元。通过局部应用每种MCN1共同递质，并在刺激MCN1期间对每种共同递质的作用进行药理学操纵，我们发现MCN1对胃磨中央模式发生器（CPG）具有不同的共同递质作用，该发生器包括外侧胃神经元（LG）和中间神经元1（Int1），以及MCN1的STG终末（MCN1(STG)）。MCN1仅使用CabTRP Ia来影响LG，而仅使用GABA来影响Int1和对侧的MCN1(STG)。这些MCN1的作用导致LG缓慢兴奋、Int1快速兴奋以及MCN1(STG)快速抑制。MCN1释放的促肠肌肽对胃磨CPG没有直接影响，尽管它可能通过对幽门节律的影响间接调节该CPG。MCN1似乎对胃磨跟随运动神经元没有离子otropic作用，但它确实使用促肠肌肽和/或CabTRP Ia来兴奋它们。因此，一个调节性投射神经元可以通过使用具有不同作用时间进程的不同共同递质，同时影响不同的CPG神经元，从而引发节律性运动活动。
