Baroreflex responses to activity at different temperatures in the South American rattlesnake, Crotalus durissus

Author(s)

Filogonio, Renato ^{[1, 2]} ; Neto, Antonio V. G. S. ^[1] ; Zamponi, Mariana M. ^[1] ; Abe, Augusto S. ^[2] ; Leite, Cleo A. C. ^[1]

Affiliation

^[1] Fed Univ Sao Carlos UFSCar, Dept Physiol Sci, Sao Carlos, SP - Brazil

^[2] State Univ Sao Paulo UNESP, Dept Zool, Rio Claro, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL; v. 191, n. 5 AUG 2021.
• Web of Science Citations: 0

Abstract

In humans, physical exercise imposes narrower limits for the heart rate (f(H)) response of the baroreflex, and vascular modulation becomes largely responsible for arterial pressure regulation. In undisturbed reptiles, the baroreflex-related f(H) alterations at the operating point (G(op)) decreases at elevated body temperatures (T-b) and the vascular regulation changes accordingly. We investigated how the baroreflex of rattlesnakes, Crotalus durissus, is regulated during an activity at different T-b, expecting that activity would reduce the capacity of the cardiac baroreflex neural pathway to buffer arterial pressure fluctuations while being compensated by the vascular neural pathway regulation. Snakes were catheterized for blood pressure assessment at three different T-b: 15, 20 and 30 degrees C. Data were collected before and after activity at each T-b. Baroreflex gain (G(op)) was assessed with the sequence method; the vascular limb, with the time constant of pressure decay (tau), using the two-element Windkessel equation. Both G(op) and tau reduced when T-b increased. Activity also reduced G(op) and tau in all T-b. The relationship between tau and pulse interval (tau/PI) was unaffected by the temperature at resting snakes, albeit it reduced after activity at 20 degrees C and 30 degrees C. The unchanged tau/PI and normalized G(op) at different T-b indicated those variables are actively adjusted to work at different f(H) and pressure conditions at rest. Our data suggest that during activity, the baroreflex-related f(H) response is attenuated and hypertension is buffered by a disproportional increase in the rate which pressure decays during diastole. This compensation seems especially important at higher T-b where G(op) is already low. (AU)

• FAPESP's process: 16/20158-6 - Cardiovascular morpho-functional adaptations for allometric scaling of arterial blood pressures to body mass in reptiles
• Grantee: Renato Filogonio
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/22016-2 - Barroreflex modulation to support the specific dynamic action in Lithobates catesbeianus
• Grantee: Mariana Medeiros Zamponi
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 18/05035-0 - Cardiovascular regulation in Squamates: validation of the decerebrated rattlesnake model for studies on regulatory processes of the cardiovascular system
• Grantee: Cléo Alcantara Costa Leite
• Support Opportunities: Regular Research Grants