Long-term facilitation of expiratory and sympathetic activities following acute intermittent hypoxia in rats

Author(s)

Lemes, E. V. ^[1] ; Aiko, S. ^[2] ; Orbem, C. B. ^[2] ; Formentin, C. ^[2] ; Bassi, M. ^[1] ; Colombari, E. ^[1] ; Zoccal, D. B. ^[1]

Affiliation

^[1] Sao Paulo State Univ UNESP, Dept Physiol & Pathol, Sch Dent Araraquara, Rua Humaita 1680, BR-14801903 Araraquara, SP - Brazil

^[2] Univ Fed Santa Catarina, Dept Physiol Sci, Ctr Biol Sci, Florianopolis, SC - Brazil

• Document type: Journal article
• Source: ACTA PHYSIOLOGICA; v. 217, n. 3, p. 254-266, JUL 2016.
• Web of Science Citations: 9

Abstract

AimAcute intermittent hypoxia (AIH) promotes persistent increases in ventilation and sympathetic activity, referred as long-term facilitation (LTF). Augmented inspiratory activity is suggested as a major component of respiratory LTF. In this study, we hypothesized that AIH also elicits a sustained increase in expiratory motor activity. We also investigated whether the expiratory LTF contributes to the development of sympathetic LTF after AIH. MethodsRats were exposed to AIH (10x6-7% O-2 for 45s, every 5min), and the cardiorespiratory parameters were evaluated during 60min using invivo and insitu approaches. ResultsIn unanesthetized conditions (n=9), AIH elicited a modest but sustained increase in baseline mean arterial pressure (MAP, 1042 vs. 111 +/- 3mmHg, P<0.05) associated with enhanced sympathetic and respiratory-related variabilities. In the insitu preparations (n=9), AIH evoked LTF in phrenic (33 +/- 12%), thoracic sympathetic (75 +/- 25%) and abdominal nerve activities (69 +/- 14%). The sympathetic overactivity after AIH was phase-locked with the emergence of bursts in abdominal activity during the late-expiratory phase. In anesthetized vagus-intact animals, AIH increased baseline MAP (113 +/- 3 vs. 122 +/- 2mmHg, P<0.05) and abdominal muscle activity (535 +/- 94%), which were eliminated after pharmacological inhibition of the retrotrapezoid nucleus/parafacial respiratory group (RTN/pFRG). ConclusionThese findings indicate that increased expiratory activity is also an important component of AIH-elicited respiratory LTF. Moreover, the development of sympathetic LTF after AIH is linked to the emergence of active expiratory pattern and depends on the integrity of the neurones of the RTN/pFRG. (AU)

• FAPESP's process: 13/17251-6 - Neural mechanisms generating the respiratory pattern and the respiratory-sympathetic coupling in conditions of hypoxia
• Grantee: Daniel Breseghello Zoccal
• Support type: Research Grants - Young Investigators Grants
• FAPESP's process: 09/54888-7 - Neural mechanisms involved on chemoreception
• Grantee: Eduardo Colombari
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 14/06976-2 - Involvement of serotoninergic mechanisms of the retrotrapezoid nucleus in the sympathetic and respiratory changes induced by intermitente hypoxia
• Grantee: Eduardo Vieira Lemes
• Support type: Scholarships in Brazil - Doctorate