Analysis of neural mechanisms of rhythm generation for sucking -induction of optical imaging method in in vitro preparations obtained from newborn mice.

新生哺乳动物中枢神经系统体外研究的最新进展，为吸吮、呼吸和运动中枢节律的生理学研究提供了重要的工具。本研究的目的是开发一种体外中枢神经系统制剂，它包括产生节律性吸吮样活动的神经回路，适用于使用电压敏感或钙敏感染料的神经元活动的光学测量。实验是在分离的脑干-脊髓标本上进行的，这些标本来自与口面部结构有或没有完整神经连接的新生小鼠。用抽吸电极监测三叉神经、面神经和舌下神经的神经活动。用CCD摄像系统记录面部、舌头和颌骨的运动。结果表明：(1)NMDA在三叉神经、面神经和舌下神经引起节律性爆发活动；(2)NMDA还引起下颌、颊和舌的节律性运动；(3)在三叉神经和面神经之间以及在桥髓交界处完全切断脑干后，NMDA仍在三叉神经、面神经和舌下神经引起节律性活动。这些结果表明，三叉神经、面神经和舌下神经运动神经元的节律性活动的振荡器分别存在于脑干的不同水平，并且每组振荡器及其下游运动神经元都包括在体外中枢神经系统制剂的一小块中，该制剂足够薄，可以用光学成像方法记录神经元的活动。

The recent development of in vitro CNS preparations of newborn mammals has provided important tools for physiological investigation of central rhythm generation of sucking as well as respiration and locomotion. The aim of this research was to develop an in vitro CNS preparation, which included neural circuits to generate rhythmic sucking-like activity, applicable to optical measuring of neuronal activity using voltage-sensitive or calcium-sensitive dyes. Experiments were performed on brainstem-spinal cord preparations isolated from newborn mice with or without the intact neural connection to the oro-facial structure. Neural activities were monitored from the trigeminal, facial and hypoglossal nerves with suction electrodes. Movements of face, tongue and jaw were recorded with a CCD camera system. The following results were obtained : (1) NMDA induced rhythmical burst activity in the trigeminal, facial and hypoglossal nerves ; (2) NMDA also induced rhythmic movements of the mandible, cheek and tongue ; (3) after complete transections of the brainstem between the trigeminal and facial nerves as well as at the pontomedullary junction, NMDA still induced the rhythmic activity in each of the trigeminal, facial and hypoglossal nerves. These results demonstrate that separate oscillators for rhythmic NMDA-induced activities in the trigeminal, facial and hypoglossal motoneurons are present at the respective levels of the brainstem, and that each set of these oscillators and their downstream motoneurons is included within a small block of an in vitro CNS preparation which is thin enough to record neuronal activities with optical imaging methods.