Figure 17. Chemoreception in wakefulness.

A schematic model for central chemoreception in wakefulness that represents our current working hypothesis. The areas in red represent sites at which focal acidification by dialysis with aCSF equilibrated with high CO₂ produced an increase in ventilation in wakefulness. The areas in gray represent sites at which we anticipate a response to focal acidification in wakefulness. Solid lines show established functional connections related to chemoreception, e.g., dialysis of an OX1R antagonist at the RTN decreased the CO₂ response in wakefulness. Dotted lines show likely connections that remain to be established. That linking the caudal MR to the PBC reflects observations obtained in a slice preparation. The red line between the caudal MR and the RTN reflects a CO₂ linked connection, i.e., focal acidification of the caudal MR enhances the response to focal acidification of the RTN. Abbreviations are: LH, a designation that includes orexin neurons in lateral hypothalamus, dorsomedial hypothalamus and perifornical area; LC, locus ceruleus; CB, carotid body; NTS, nucleus tractus solitarius; PBC, pre-Bötzinger complex; RTN, retrotrapezoid nucleus; MR, medullary raphe; VLM, ventrolateral medulla. Nattie & Li, (169) J. Appl. Physiol. 2010, used with permission.