he baroreflex in aquatic and amphibious teleosts: Does terrestriality represent a significant driving force for the evolution of a more effective baroreflex in vertebrates

Author(s)

Armelin, Vinicius Araujo ^{[1, 2, 3]} ; da Silva Braga, Victor Hugo ^{[1, 2]} ; Teixeira, Mariana Teodoro ^{[1, 2]} ; Guagnoni, Igor Noll ^{[1, 2]} ; Wang, Tobias ^{[1, 4]} ; Florindo, Luiz Henrique ^{[1, 2, 5]}

Affiliation

^[1] Natl Inst Sci & Technol Comparat Physiol INCT FAP, Sao Paulo - Brazil

^[2] Sao Paulo State Univ UNESP, Dept Zool & Bot, Rua Cristovao Colombo 2265, BR-15054000 Sao Jose Do Rio Preto, SP - Brazil

^[3] Univ Sao Paulo, Inst Biosci, Dept Physiol, Rua Matao, Travessa 14, 321, BR-05508090 Sao Paulo, SP - Brazil

^[4] Aarhus Univ AU, Dept Biosci, Sect Zoophysiol, CF Mollers 3, DK-8000 Aarhus C - Denmark

^[5] Sao Paulo State Univ UNESP, Aquaculture Ctr CAUNESP, Rodovia Prof Paulo Donato Castellane N-N, BR-14884900 Jaboticabal, SP - Brazil

• Document type: Journal article
• Source: COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY; v. 255, MAY 2021.
• Web of Science Citations: 0

Abstract

All vertebrates have baroreflexes that provide fast regulation of arterial blood pressure (P-A) to maintain adequate tissue perfusion and avoid vascular lesions from excessive pressures. The baroreflex is a negative feedback loop, where altered P-A results in reciprocal changes in heart rate (f(H)) and systemic vascular conductance to restore pressure. In terrestrial environments, gravity usually leads to blood pooling in the lower body reducing venous return, cardiac filling, cardiac output and P-A. Conversely, in aquatic environments, the hydrostatic pressure of surrounding water mitigates blood pooling and prevents vascular distensions. In this context, we aimed to test the hypothesis that vertebrate species that were exposed to gravity-induced hemodynamic disturbances throughout their evolutionary histories have a more effective barostatic reflex than those that were not. We examined the cardiac baroreflex of fish that perform (Clarias gariepinus and Hoplerythrinus unitaeniatus) and do not perform (Hoplias malabaricus and Oreochromis niloticus) voluntary terrestrial sojourns, using pharmacological manipulations of P-A to characterize reflex changes in f(H) using a four-variable sigmoidal logistic function (i.e. the ``Oxford technique{''}). Our results revealed that amphibious fish exhibit higher baroreflex gain and responsiveness to hypotension than strictly aquatic fish, suggesting that terrestriality and the gravitational circulatory stresses constitute a relevant driving force for the evolution of a more effective baroreflex in vertebrates. We also demonstrate that strictly aquatic teleosts have considerable baroreflex gain, supporting the view that the baroreflex is an ancient cardiovascular trait that appeared before vertebrates colonized the gravity-dominated realm of land. (AU)

• FAPESP's process: 16/17572-5 - The parasympathetic cardiac modulation in the Tambaqui(Colossoma macropomum): The unequal influences of the right and left vagus nerve
• Grantee: Victor Hugo da Silva Braga
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 08/57712-4 - The National Institute of Comparative Physiological Research
• Grantee: Augusto Shinya Abe
• Support Opportunities: Research Projects - Thematic Grants