Evans C G, Cropper E C
Department of Physiology and Biophysics, The Mount Sinai Medical Center, New York, New York 10029, USA.
J Neurosci. 1998 Oct 1;18(19):8016-31. doi: 10.1523/JNEUROSCI.18-19-08016.1998.
Although central pattern generators (CPGs) can produce rhythmic activity in isolation, it is now generally accepted that under physiological conditions information from the external and internal environment is incorporated into CPG-induced motor programs. Experimentally advantageous invertebrate preparations may be particularly useful for studies that seek to characterize the cellular mechanisms that make this possible. In these experiments, we study sensorimotor integration in the feeding circuitry of the mollusc Aplysia. We show that a premotor neuron with plateau properties, B51, is important for generating the radula closing/retraction phase of ingestive motor programs. When B51 is depolarized in semi-intact preparations, radula closing/retractions are enhanced. When B51 is hyperpolarized, radula closing/retractions are reduced in size. In addition to being important as a premotor interneuron, B51 is also a sensory neuron that is activated when the feeding apparatus, the radula, rotates backward. The number of centripetal spikes in B51 is increased if the resistance to backward rotation is increased. Thus, B51 is a proprioceptor that is likely to be part of a feedback loop that insures that food will be moved into the buccal cavity when difficulty is encountered. Our data suggest, therefore, that Aplysia are able to adjust feeding motor programs to accommodate the specific qualities of the food ingested because at least one of the neurons that generates the basic ingestive motor program also serves as an on-line monitor of the success of radula movements.
虽然中枢模式发生器（CPG）能够独立产生节律性活动，但现在人们普遍认为，在生理条件下，来自外部和内部环境的信息会被整合到CPG诱导的运动程序中。实验上具有优势的无脊椎动物标本对于旨在表征实现这一过程的细胞机制的研究可能特别有用。在这些实验中，我们研究了软体动物海兔进食回路中的感觉运动整合。我们发现，具有平台特性的运动前神经元B51对于产生摄食运动程序的齿舌闭合/回缩阶段很重要。在半完整标本中使B51去极化时，齿舌闭合/回缩会增强。当B51超极化时，齿舌闭合/回缩的幅度会减小。除了作为运动前中间神经元很重要外，B51还是一个感觉神经元，当进食器官齿舌向后旋转时会被激活。如果增加对向后旋转的阻力，B51中的向心尖峰数量会增加。因此，B51是一种本体感受器，可能是反馈回路的一部分，可确保在遇到困难时食物能被移入口腔。所以，我们的数据表明，海兔能够调整摄食运动程序以适应所摄取食物的特定性质，因为至少一个产生基本摄食运动程序的神经元还充当齿舌运动成功与否的在线监测器。
