title: Effects of maturation and acidosis on the chaos-like complexity of the neural respiratory output in the isolated brainstem of the tadpole, Rana esculenta.
abstract: Human ventilation at rest exhibits mathematical chaos-like complexity that can be described as long-term unpredictability mediated (in whole or in part) by some low-dimensional nonlinear deterministic process. Although various physiological and pathological situations can affect respiratory complexity, the underlying mechanisms remain incompletely elucidated. If such chaos-like complexity is an intrinsic property of central respiratory generators, it should appear or increase when these structures mature or are stimulated. To test this hypothesis, we employed the isolated tadpole brainstem model [Rana (Pelophylax) esculenta] and recorded the neural respiratory output (buccal and lung rhythms) of pre- (n = 8) and postmetamorphic tadpoles (n = 8), at physiologic (7.8) and acidic pH (7.4). We analyzed the root mean square of the cranial nerve V or VII neurograms. Development and acidosis had no effect on buccal period. Lung frequency increased with development (P < 0.0001). It also increased with acidosis, but in postmetamorphic tadpoles only (P < 0.05). The noise-titration technique evidenced low-dimensional nonlinearities in all the postmetamorphic brainstems, at both pH. Chaos-like complexity, assessed through the noise limit, increased from pH 7.8 to pH 7.4 (P < 0.01). In contrast, linear models best fitted the ventilatory rhythm in all but one of the premetamorphic preparations at pH 7.8 (P < 0.005 vs. postmetamorphic) and in four at pH 7.4 (not significant vs. postmetamorphic). Therefore, in a lower vertebrate model, the brainstem respiratory central rhythm generator accounts for ventilatory chaos-like complexity, especially in the postmetamorphic stage and at low pH. According to the ventilatory generators homology theory, this may also be the case in mammals.
authors.affiliation: Service Central d'Explorations Fonctionnelles Respiratoires, Groupe Hospitalier Pitie-Salpetriere, 47-83 Boulevard de l'Hôpital, Paris Cedex 13, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Straus
authors.forename: Ziyad
authors.initials: Z
authors.lastname: Samara
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Fiamma
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bautin
authors.forename: Anja
authors.initials: A
authors.lastname: Ranohavimparany
authors.forename: Patrick
authors.initials: P
authors.lastname: Le Coz
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Golmard
authors.forename: Pierre
authors.initials: P
authors.lastname: Darré
authors.forename: Marc
authors.initials: M
authors.lastname: Zelter
authors.forename: Chi-Sang
authors.initials: CS
authors.lastname: Poon
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
mesh_terms: D000138:Acidosis / Q000503:physiopathology*; D000200:Action Potentials; D000704:Analysis of Variance; D000818:Animals; D002610:Cheek / Q000294:innervation*; D003391:Cranial Nerves / Q000503:physiopathology*; D004195:Disease Models, Animal; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007814:Larva; D016014:Linear Models; D008168:Lung / Q000294:innervation*; D008954:Models, Biological; D017711:Nonlinear Dynamics; D010507:Periodicity; D011893:Rana esculenta; D012119:Respiration; D012125:Respiratory Center / Q000503:physiopathology*; D056152:Respiratory Rate; D013997:Time Factors