Studies of the respiratory center using isolated brainstem-spinal cord preparations.

It has been ten years since a brainstem-spinal cord preparation isolated from a newborn rat was introduced for study of the mammalian respiratory center. Here, I briefly summarize first, these studies, which include the tissue condition of in vitro preparations, respiratory reflexes, pharmacology, rhythm generation, respiratory chemoreception, phrenic motoneurons, regulation from pons, and development of a respiratory center. In the latter half of this paper, I focus on the neural mechanisms of respiratory rhythm generation. A current hypothesis for the central pattern generator of respiration proposed by the author's group is that the respiratory rhythm generator, composed of pre-inspiratory neurons in the rostral ventrolateral medulla, produces the primary rhythm of respiration and triggers an inspiratory pattern generator composed of inspiratory neurons in the rostral and the caudal ventrolateral medulla.