抄録
The central chemoreceptor activation evokes the abdominal expiratory activity in the in vitro brainstem-spinal cord-rib preparation from neonatal rats (Iizuka, J Physiol, 551.2: 617-633, 2003). This expiratory activity is limited to the first part of the expiratory phase in most of preparations. In the anesthetized, vagotomized, paralyzed and artificially ventilated adult rat, the abdominal activity showed a plateau pattern during the expiratory phase or a gradually augmenting pattern with abrupt termination upon the onset of the inspiratory activity under hypercapnia. Similar results were obtained in the anesthetized neonatal rat. Although the expiratory motor pattern in detail was different between the in vitro and in vivo conditions, thus, the fundamental alternating pattern between inspiratory and expiratory motor activity was well preserved in the in vitro preparation. Since the abdominal muscle showed weak or no expiratory activity during the anoxia-induced gasping in the in vivo neonatal rat preparation, the respiratory activity in the in vitro preparation is not equal to the gasping. Furthermore, our recent study suggested that the neuronal mechanisms needed to generate the rostrocaudal gradient in the inspiratory and expiratory motor output to various rib-cage muscles should be intact in the in vitro preparation (Iizuka, Neurosci Res, 50: 263-269, 2004). The advantages and limitations of the in vitro preparation for the study of the respiratory motor pattern generation will be discussed. I will also refer the possible factors for such distortion of the expiratory motor pattern under the in vitro conditions. [Jpn J Physiol 55 Suppl:S63 (2005)]
