[Localization and function of the brainstem neuronal mechanism for respiratory control].

Recently, the neural mechanism of respiratory control in the brainstem has been extensively analyzed mainly in vitro. A neuronal group in the ventrolateral medulla, the ventral respiratory group (VRG), is important in respiratory rhythm and pattern generation. A small region in the rostral VRG, the pre-Bötzinger Complex (pre-BötC), is the kernel of respiratory rhythmogenesis. A novel region ventrolateral to the facial nucleus, the para-facial respiratory group (pFRG), was found and has been considered to also generate respiratory rhythm. These two oscillators, pre-BötC and pFRG, are coupled and synchronized. In central chemoreception, small cells surrounding fine vessels in the most superficial layer in the rostral ventral medulla are considered to be primary chemoreceptor cells. Currently, several kinds of neurotransmitters, including glutamic acid, serotonin, ATP and acetylcholine, are considered to play important roles in the signal transduction from chemoreceptor cells to the VRG and other parts of the respiratory neuronal network. The mechanism of respiratory suppression by opioids is the blockade of excitatory drive to the pre-BötC. Although recently we have elucidated that propofol, widely used intravenous anesthetics, suppresses respiratory output through the activation of GABAA receptor, the mechanism of respiratory depression by inhalation anesthetics remains unknown.