title: Curtailed respiration by repeated vs. isolated hypoxia in maturing piglets is unrelated to NTS ME or SP levels.
abstract: In early development, respiratory disorders can produce recurring hypoxic episodes during sleep. To examine possible effects of daily repeated vs. isolated hypoxic hypoxia, cardiorespiratory functions and central, respiratory-related neuromodulator levels in 21- to 32-day-old, chronically instrumented, unsedated piglets were compared between a fifth sequential daily hypoxia and an isolated hypoxia (10% O2-90% N2 for 30 min). Diaphragmatic electromyographic activity, heart rate and arterial pressure, and pH and gas tensions were measured. In vivo microdialysis, via chronically implanted guides, served to sample interstitial substance P (SP) and methionine-enkephalin (ME) at the level of the respiratory-related nucleus tractus solitarii (NTS). Compared with an isolated hypoxia, repeated hypoxia resulted in 1) lower respiratory frequency (f), ventilation equivalent, and arterial pH, higher arterial PO2 during hypoxia, and lower f in recovery from hypoxia; and 2) increased SP concentrations but no change in ME concentrations. We conclude that, in these maturing swine, repeated vs. isolated hypoxic exposure curtails respiratory responses to hypoxia by a mechanism(s) unrelated to SP or ME levels at the NTS.
authors.affiliation: Department of Pediatrics, McGill University, and The Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada H3H 1P3.
authors.forename: K A
authors.initials: KA
authors.lastname: Waters
authors.forename: A
authors.initials: A
authors.lastname: Laferrière
authors.forename: J
authors.initials: J
authors.lastname: Paquette
authors.forename: C
authors.initials: C
authors.lastname: Goodyer
authors.forename: I R
authors.initials: IR
authors.lastname: Moss
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000502:physiology*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D005260:Female; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D012008:Recurrence; D012119:Respiration; D017552:Solitary Nucleus / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*; D013552:Swine; D013556:Swine, Miniature
chemical_list: D013373:Substance P; D004744:Enkephalin, Methionine