Sahley C L, Modney B K, Boulis N M, Muller K J
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
J Neurosci. 1994 Nov;14(11 Pt 1):6715-21. doi: 10.1523/JNEUROSCI.14-11-06715.1994.
Sensory neurons in the leech excite the S interneuron, which in turn excites motoneurons that shorten the leech, although activity in the S cell reportedly cannot by itself shorten the animal. Experiments were performed in semi-intact leeches using established dishabituation and sensitization protocols. S-cell activity increased during reflexive shortening once the animal was sensitized or dishabituated with a strong shock. S-cell activity otherwise was not associated with shortening. To test the role of the S-cell in dishabituation and sensitization of the shortening reflex, single S cells were ablated in vivo by intracellular injections of pronase. S-cell lesions reduced but did not eliminate dishabituation; however, sensitization was completely disrupted. This was consistent with recent evidence that separate processes contribute to dishabituation and sensitization. Since the S cell in each ganglion is a link in a rapidly conducting chain along the length of the animal, it may be sufficient to break the chain at a single point to eliminate sensitization.
水蛭中的感觉神经元会刺激S中间神经元，而S中间神经元又会刺激运动神经元，使水蛭身体缩短，不过据报道，S细胞自身的活动并不能让水蛭身体缩短。实验是在半完整的水蛭身上进行的，采用了既定的去习惯化和敏感化方案。一旦动物被强烈电击致敏或去习惯化，在反射性缩短过程中，S细胞的活动就会增加。否则，S细胞的活动与身体缩短并无关联。为了测试S细胞在缩短反射的去习惯化和敏感化中的作用，通过细胞内注射链霉蛋白酶在体内消融单个S细胞。S细胞损伤减少了去习惯化，但并未消除；然而，敏感化被完全破坏了。这与最近的证据一致，即不同的过程导致去习惯化和敏感化。由于每个神经节中的S细胞是沿着动物身体长度的快速传导链中的一个环节，在单个点上打断这条链可能就足以消除敏感化。
