title: Effects of short term forced oral breathing: physiological changes and structural adaptation of diaphragm and orofacial muscles in rats.
abstract: OBJECTIVE
  We studied adaptation of diaphragm and orofacial muscles as well as hormonal responses to forced oral breathing (lasting for only 4 days) following reversible bilateral nasal obstruction performed on day 8 post-natal male rats.
  
  
  METHODS
  Muscle myosin heavy chain (MHC) composition and hormone levels were analysed during two periods: 1 and 3 days after obstruction (days 9 and 11 post-natal), and following 3 months recovery with nasal breathing (90 days, adult).
  
  
  RESULTS
  Diaphragm muscle showed significant increases in adult isoforms (MHC 1, 2a) in oral breathing group versus control. We observed increases in MHC neonatal and adult type 1 isoforms in muscles involved with oral breathing, masseter superficialis and anterior digastric. No changes were observed in the levator nasolabialis muscle involved with nasal breathing. Reversible nasal obstruction was associated with reduced growth of the olfactory bulbs lasting into adulthood, and an initial decrease in lung growth followed by recovery at 90 days. Adrenal hypertrophy was observed after 1 day of nasal obstruction and lasted into adulthood. The "stress" hormone response was variable, increased (over 1000%) during the obstruction but normal by adulthood. An increase in plasma testosterone was observed during the obstruction, and a decrease in thyroid hormone levels throughout.
  
  
  CONCLUSIONS
  Very short term nasal obstruction, i.e. forced oral breathing, leads to long term hormonal changes and respiratory muscle fibre adaptation.
authors: Université H. Poincaré, B.P.70239, 54506 Vandoeuvre-les-Nancy, France.
authors: Guy Stéphane
authors: GS
authors: Padzys
authors: Jean-Marc
authors: JM
authors: Martrette
authors: Christiane
authors: C
authors: Tankosic
authors: Simon Nigel
authors: SN
authors: Thornton
authors: Marie
authors: M
authors: Trabalon
mesh_terms: D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D003964:Diaphragm / Q000503:physiopathology*; D004587:Electrophoresis, Agar Gel; D005152:Facial Muscles / Q000503:physiopathology*; D008297:Male; D009058:Mouth Breathing; D018995:Myosin Heavy Chains / Q000097:blood*; D015508:Nasal Obstruction; D009830:Olfactory Bulb / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000097:blood*; D013963:Thyroid Hormones / Q000097:blood*
chemical_list: D013963:Thyroid Hormones; D013739:Testosterone; D018995:Myosin Heavy Chains