title: Focal microdialysis of CO₂ in the perifornical-hypothalamic area increases ventilation during wakefulness but not NREM sleep.
abstract: We investigated whether the perifornical-lateral hypothalamic area (PF-LHA), where the orexin neurons reside, is a central chemoreceptor site by microdialysis of artificial cerebrospinal fluid (aCSF) equilibrated with 25% CO(2) into PF-LHA in conscious rats. This treatment is known to produce a focal tissue acidification like that associated with a 6-7 mm Hg increase in arterial [Formula: see text] . Such focal acidification in the PF-LHA significantly increased ventilation up to 15% compared with microdialysis of normal aCSF equilibrated with 5% CO(2) only in wakefulness but not in sleep in both the dark (P=0.004) and light (P<0.001) phases of the diurnal cycle. This response was predominantly due to a significant increase in respiratory frequency (11%, P<0.001). There were no significant effects on ventilation in the group with probes misplaced outside the PF-LHA. These results suggest that PF-LHA functions as a central chemoreceptor site in the central nervous system in a vigilant state dependent manner with predominant effects in wakefulness.
authors.affiliation: Department of Physiology and Neurobiology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, United States. Ningjing.Li@dartmouth.edu
authors.forename: Ningjing
authors.initials: N
authors.lastname: Li
authors.forename: Aihua
authors.initials: A
authors.lastname: Li
authors.forename: Eugene
authors.initials: E
authors.lastname: Nattie
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D004569:Electroencephalography; D004576:Electromyography; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D009434:Neural Pathways / Q000502:physiology; D017397:Prefrontal Cortex / Q000378:metabolism*; D012123:Pulmonary Ventilation / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012894:Sleep Stages / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide