title: The Kölliker-Fuse nucleus acts as a timekeeper for late-expiratory abdominal activity.
abstract: While the transition from the inspiratory to the post-inspiratory (post-I) phase is dependent on the pons, little attention has been paid to understanding the role of the pontine respiratory nuclei, specifically the Kölliker-Fuse nucleus (KF), in transitioning from post-I to the late expiratory (late-E) activity seen with elevated respiratory drive. To elucidate this, we used the in situ working heart-brainstem preparation of juvenile male Holtzman rats and recorded from the vagus (cVN), phrenic (PN) and abdominal nerves (AbN) during baseline conditions and during chemoreflex activation [with potassium cyanide (KCN; n=13) or hypercapnia (8% CO2; n=10)] to recruit active expiration. Chemoreflex activation with KCN increased PN frequency and cVN post-I and AbN activities. The inhibition of KF with isoguvacine microinjections (10mM) attenuated the typical increase in PN frequency and cVN post-I activity, and amplified the AbN response. During hypercapnia, AbN late-E activity emerged in association with a significant reduction in expiratory time. KF inhibition during hypercapnia significantly decreased PN frequency and reduced the duration and amplitude of post-I cVN activity, while the onset of the AbN late-E bursts occurred significantly earlier. Our data reveal a negative relationship between KF-induced post-I and AbN late-E activities, suggesting that the KF coordinates the transition between post-I to late-E activity during conditions of elevated respiratory drive.
authors.affiliation: Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada. Electronic address: jenkin@zoology.ubc.ca.
authors.forename: Sarah E M
authors.initials: SE
authors.lastname: Jenkin
authors.affiliation: Department of Zoology, The University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: William K
authors.initials: WK
authors.lastname: Milsom
authors.affiliation: School of Dentistry of Araraquara, São Paulo State University, Araraquara, Brazil.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Zoccal
mesh_terms: D000005:Abdomen / Q000294:innervation*; D000818:Animals; D045853:Exhalation / Q000187:drug effects / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology*; D001239:Inhalation / Q000187:drug effects / Q000502:physiology*; D065836:Kolliker-Fuse Nucleus / Q000502:physiology; D008297:Male; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology*; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology*
chemical_list: D011190:Potassium Cyanide
keywords: Kölliker–Fuse; active expiration; hypercapnia; hypoxia; pons; post-inspiration