Baroreflex and cardiorespiratory regulation in the facultative air-breathing teleost Pangasianodon hypophthalmus

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  • Mikkel Thomsen
  • ,
  • Vinicius Araujo Armelin
  • ,
  • Mariana Teodoro Teixeira
  • ,
  • Luiz Henrique Florindo, Brazil
  • Mark Bayley
  • Tobias Wang
All vertebrates possess baroreceptors monitoring arterial blood pressure and eliciting reflexive changes in vascular resistance and heart rate in response to blood pressure perturbations imposed by e.g. exercise, hypoxia, or hemorrhage. In this study, we investigated the cardiorespiratory regulation in the facultative air-breathing catfish Pangasianodon hypophthalmus. Using a pharmacological approach, we quantified the cardiac limb of the baroreflex and by subjecting fish to hypoxia and by stimulation with NaCN with and without pharmacological autonomic blockade, we examined the cardiovascular regulation associated with air-breathing. As in other air-breathing fish, there was a substantial heart rate variability associated with air-breathing. Here, we demonstrate that this heart rate variability is abolished with cholinergic muscarinic pharmacological blockade, which also abolished the cardiac limb of the baroreflex, and consequently, the fish fail to maintain their arterial blood pressure when air-breathing. In higher vertebrate classes, baroreceptors elicit ventilatory changes, however, whether this is the case in fish has not previously been investigated. P. hypophthalmus demonstrated a prominent increase in ventilation during imposed hypotension, however, it remains unclear whether this is due to a stimulation of baroreceptors or direct stimulation of chemoreceptors. Collectively, these results demonstrate, for the first time, an efficient baroreflex in an air-breathing fish, suggest involvement of baroreceptors in heart rate regulation during air-breathing, and show a correlation between blood pressure and ventilation, providing additional information on the origin of this link.
Original languageEnglish
JournalJournal of Comparative Physiology
Publication statusIn preparation - 23 Jan 2019

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