Sadamoto H, Hatakeyama D, Kojima S, Fujito Y, Ito E
Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Neurosci Res. 1998 Sep;32(1):57-63. doi: 10.1016/s0168-0102(98)00066-2.
To examine whether nitric oxide (NO)-generative neurons are included in the central circuitry for generation of feeding pattern in the pond snail, Lymnaea stagnalis, two staining techniques for NADPH diaphorase and serotonin (5-HT) were applied for its central nervous system (CNS). The former technique is known to show localization of NO synthase; the latter is well employed as a marker for the feeding circuitry because 5-HT is a main transmitter in it. In the buccal ganglion, B2 motoneuron was found to be a putative NO-generative neuron. This motoneuron is not involved directly in the coordination of feeding pattern but is activated simultaneously with the feeding to control the oesophageal and gut tissues for the digestion. Taking account of the diffusion effects of NO, the NO released from B2 motoneuron, when the feeding is started, is thought to sufficiently modulate the feeding circuitry. In the cerebral ganglion, the superior lip nerve, the median lip nerve and the tentacle nerve included both putative NO-generative fibers and serotonergic fibers. These fibers are not identical, but the NO released in the nerves may activate the serotonergic fibers, resulting in the influence upon the initiation of the feeding. Therefore, our present findings clearly showed that NO is not involved in transmission within the central circuitry for the feeding, but suggested that NO can crucially affect the feeding behavior, such as initiation and modulation of the feeding pattern.
为了研究在椎实螺（Lymnaea stagnalis）中，一氧化氮（NO）生成神经元是否包含在产生摄食模式的中枢神经回路中，对其中枢神经系统（CNS）应用了两种针对还原型辅酶II黄递酶和5-羟色胺（5-HT）的染色技术。已知前一种技术可显示一氧化氮合酶的定位；后一种技术被广泛用作摄食回路的标记，因为5-HT是其中的主要神经递质。在口神经节中，发现B2运动神经元是一个假定的NO生成神经元。该运动神经元并不直接参与摄食模式的协调，但在摄食时会同时被激活，以控制食管和肠道组织进行消化。考虑到NO的扩散效应，当摄食开始时，从B2运动神经元释放的NO被认为足以调节摄食回路。在脑神经节中，上唇神经、中唇神经和触手神经既包含假定的NO生成纤维，也包含5-羟色胺能纤维。这些纤维并不相同，但神经中释放的NO可能会激活5-羟色胺能纤维，从而影响摄食的启动。因此，我们目前的研究结果清楚地表明，NO不参与摄食中枢回路中的信号传递，但表明NO可关键地影响摄食行为，如摄食模式的启动和调节。
