Artigo
Autonomic control of post-air-breathing tachycardia in Clarias gariepinus
Registro en:
Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology, v. 185, n. 6, p. 669-676, 2015.
0174-1578
10.1007%2Fs00360-015-0910-z
2797832406818407
Autor
Teixeira, Mariana Teodoro [UNESP]
Armelin, Vinicius Araújo
Abe, Augusto Shinya [UNESP]
Rantin, Francisco Tadeu
Florindo, Luiz Henrique [UNESP]
Resumen
The African catfish (Clarias gariepinus) is a teleost with bimodal respiration that utilizes a paired suprabranchial chamber located in the gill cavity as an air-breathing organ. Like all air-breathing fishes studied to date, the African catfish exhibits pronounced changes in heart rate (f H) that are associated with air-breathing events. We acquired f H, gill-breathing frequency (f G) and air-breathing frequency (f AB) in situations that require or do not require air breathing (during normoxia and hypoxia), and we assessed the autonomic control of post-air-breathing tachycardia using an infusion of the β-adrenergic antagonist propranolol and the muscarinic cholinergic antagonist atropine. During normoxia, C. gariepinus presented low f AB (1.85 ± 0.73 AB h−1) and a constant f G (43.16 ± 1.74 breaths min−1). During non-critical hypoxia (PO2 = 60 mmHg), f AB in the African catfish increased to 5.42 ± 1.19 AB h−1 and f G decreased to 39.12 ± 1.58 breaths min−1. During critical hypoxia (PO2 = 20 mmHg), f AB increased to 7.4 ± 1.39 AB h−1 and f G decreased to 34.97 ± 1.78 breaths min−1. These results were expected for a facultative air breather. Each air breath (AB) was followed by a brief but significant tachycardia, which in the critical hypoxia trials, reached a maximum of 143 % of the pre-AB f H values of untreated animals. Pharmacological blockade allowed the calculation of cardiac autonomic tones, which showed that post-AB tachycardia is predominantly regulated by the parasympathetic subdivision of the autonomic nervous system. National Institute of Science and Technology in Comparative Physiology (INCT–FAPESP/CNPq), São Paulo, Brazil Department of Physiological Sciences, Federal University of São Carlos (UFSCar), Via Washington Luiz, km 235, São Carlos, SP, 13565-905, Brazil Department of Zoology and Botany, São Paulo State University (UNESP), Cristóvão Colombo Street, 2265, São José Do Rio Preto, SP, 15054-000, Brazil Department of Zoology, São Paulo State University (UNESP), 24A Avenue, 1515, Rio Claro, SP, 13506-900, Brazil