The autonomic control of upright posture tachycardia in the arboreal lizard Iguana iguana

Author(s)

Troiano, Natalia Miria ^{[1, 2]} ; Armelin, Vinicius Araujo ^{[1, 2]} ; da Silva Braga, Victor Hugo ^{[1, 2]} ; Abe, Augusto Shinya ^{[2, 3, 4]} ; Rantin, Francisco Tadeu ^{[5, 2]} ; Florindo, Luiz Henrique ^{[1, 2, 3]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Dept Zool & Bot, Rua Cristovao Colombo 2265, BR-15054000 Sao Jose Do Rio Preto, SP - Brazil

^[2] Natl Inst Sci & Technol Comparat Physiol INCT FAP, Rio Claro - Brazil

^[3] Sao Paulo State Univ UNESP, Aquaculture Ctr CAUNESP, Jaboticabal - Brazil

^[4] Sao Paulo State Univ UNESP, Dept Zool, Rio Claro - Brazil

^[5] Fed Univ Sao Carlos UFSCar, Dept Physiol Sci, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY; v. 329, n. 3, p. 130-139, MAR 2018.
• Web of Science Citations: 2

Abstract

In terrestrial environments, upright spatial orientation can dramatically influence animals' hemodynamics. Generally, large and elongated species are particularly sensitive to such influence due to the greater extent of their vascular beds being verticalized, favoring the establishment of blood columns in their bodies along with caudal blood pooling, and thus jeopardizing blood circulation through a cascade effect of reductions in venous return, cardiac filling, stroke volume, cardiac output, and arterial blood pressure. This hypotension triggers an orthostatic-(baroreflex)-tachycardia to normalize arterial pressure, and despite the extensive observation of this heart rate (f(H)) adjustment in experiments on orthostasis, little is known about its mediation and importance in ectothermic vertebrates. In addition, most of the knowledge on this subject comes from studies on snakes. Thus, our objective was to expand the knowledge on this issue by investigating it in an arboreal lizard (Iguana iguana). To do so, we analyzed f(H), cardiac autonomic tones, and f(H) variability in horizontalized and tilted iguanas (0 degrees, 30 degrees. and 60 degrees) before and after muscarinic blockade with atropine and double autonomic blockade with atropine and propranolol. The results revealed that I. Iguana exhibits significant orthostatic-tachycardia only at 60(o) inclinationsa condition that is primarily elicited by a withdrawal of vagal drive. Also, as in humans, increases in low-frequency f(H) oscillations and decreases in high-frequency f(H) oscillations were observed along with orthostatic-tachycardia, suggesting that the mediation of this f(H) adjustment may be evolutionarily conserved in vertebrates. (AU)

• FAPESP's process: 15/12156-0 - Cardiac autonomic control and the importance of orthostatic-tachycardia in green Iguana, Iguana iguana
• Grantee: Natalia Miria Troiano
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 08/57712-4 - The National Institute of Comparative Physiological Research
• Grantee: Augusto Shinya Abe
• Support Opportunities: Research Projects - Thematic Grants