Autonomic control of post-air-breathing tachycardia in Clarias gariepinus (Teleostei: Clariidae)

作者：Teixeira Mariana Teodoro; Armelin Vinicius Araujo; Abe Augusto Shinya; Rantin Francisco Tadeu; Florindo Luiz Henrique^*

来源：Journal of Comparative Physiology B-Biochemical Systems and Environmental Physiology, 2015, 185(6): 669-676.

DOI：10.1007/s00360-015-0910-z

• African catfish
• Autonomic control
• Air breathing
• Hypoxia
• Tachycardia

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 beta-adrenergic antagonist propranolol and the muscarinic cholinergic antagonist atropine. During normoxia, C. gariepinus presented low f (AB) (1.85 +/- A 0.73 AB h(-1)) and a constant f (G) (43.16 +/- A 1.74 breaths min(-1)). During non-critical hypoxia (PO2 = 60 mmHg), f (AB) in the African catfish increased to 5.42 +/- A 1.19 AB h(-1) and f (G) decreased to 39.12 +/- A 1.58 breaths min(-1). During critical hypoxia (PO2 = 20 mmHg), f (AB) increased to 7.4 +/- A 1.39 AB h(-1) and f (G) decreased to 34.97 +/- A 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.

• 出版日期2015-8