title: Localization of essential rhombomeres for respiratory rhythm generation in bullfrog tadpoles using a binary search algorithm: Rhombomere 7 is essential for the gill rhythm and suppresses lung bursts before metamorphosis.
abstract: Frog metamorphosis includes transition from water breathing to air breathing but the extent to which such a momentous change in behavior requires fundamental changes in the organization of the brainstem respiratory circuit is unknown. Here, we combine a vertically mounted isolated brainstem preparation, "the Sheep Dip," with a search algorithm used in computer science, to identify essential rhombomeres for generation of ventilatory motor bursts in metamorphosing bullfrog tadpoles. Our data suggest that rhombomere 7, which in mammals hosts the PreBötC (PreBötzinger Complex; the likely inspiratory oscillator), is essential for gill and buccal bursts. Whereas rhombomere 5, in close proximity to a brainstem region associated with the mammalian expiratory oscillator, is essential for lung bursts at both stages. Therefore, we conclude there is no rhombomeric translocation of respiratory oscillators in bullfrogs as previously suggested. In premetamorphic tadpoles, functional ablation of rhombomere 7 caused ectopic expression of precocious lung bursts, suggesting the gill oscillator suppresses an otherwise functional lung oscillator in early development.
authors.affiliation: Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Maryana
authors.initials: M
authors.lastname: Duchcherer
authors.forename: Mufaddal I
authors.initials: MI
authors.lastname: Baghdadwala
authors.forename: Jenny
authors.initials: J
authors.lastname: Paramonov
authors.forename: Richard J A
authors.initials: RJ
authors.lastname: Wilson
mesh_terms: D000465:Algorithms; D000818:Animals; D005880:Gills / Q000378:metabolism*; D007814:Larva / Q000254:growth & development; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D008675:Metamorphosis, Biological / Q000502:physiology*; D011892:Rana catesbeiana / Q000254:growth & development*; D012119:Respiration / Q000235:genetics*; D012249:Rhombencephalon / Q000254:growth & development
keywords: brainstem; respiration; rhombomere; rhythm; tadpole