title: Bicuculline dialysis in the retrotrapezoid nucleus (RTN) region stimulates breathing in the awake rat.
abstract: Muscimol dialysis in the retrotrapezoid nucleus (RTN) region of awake rats reduces tidal volume during air breathing and decreases chemoreception (Nattie, Li, 2000. J. Appl. Physiol., 89, 153-162). Is there an endogenous GABAergic inhibition of the RTN as for medullary respiratory and pressor neurons? Bicuculline microdialysis (30 min; 1 mM) into the RTN region of awake rats reversibly increased tidal volume by 11-16% over the period from 10 to 60 min (P<0.01; six rats). Ventilation increased but this was significant (P<0.05) only at 5, 20, and 25 min as frequency tended to decrease during dialysis. The ventilatory response to 7% CO(2) was unaffected (six rats); dialysis of vehicle alone over 4 h had no effect (five rats). It was concluded that in the awake rat there is ongoing endogenous modulation of RTN effects on tidal volume by a GABAergic process of unknown origin. The lack of effect on the response to systemic hypercapnia suggests that the RTN provides an ongoing endogenous drive to respiration by a process that is independent of its role in chemoreception.
authors.affiliation: Department of Physiology, Borwell Building, Dartmouth Medical School, Lebanon, NH 03756-0001, USA. eugene.nattie@dartmouth.edu
authors.forename: E
authors.initials: E
authors.lastname: Nattie
authors.forename: J
authors.initials: J
authors.lastname: Shi
authors.forename: A
authors.initials: A
authors.lastname: Li
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000008:administration & dosage* / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology; D018756:GABA Antagonists / Q000008:administration & dosage* / Q000494:pharmacology; D008526:Medulla Oblongata / Q000502:physiology*; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects*; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology
chemical_list: D018756:GABA Antagonists; D002245:Carbon Dioxide; D001640:Bicuculline