Adrenergic control of functional characteristics of the cardiovascular system in the South American rattlesnake, Crotalus durissus

Author(s)

Castro, Samanta Aparecida ; Taylor, Edwin William ; Tavares, Driele ; Leite, Cleo Alcantara Costa

• Document type: Journal article
• Source: COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY; v. 281, p. 12-pg., 2023-07-01.

Abstract

In squamate reptiles, extensive innervation of the heart and vascular beds allows for continuous modulation of the cardiovascular system by the autonomic nervous system. The systemic vasculature is the main target of excitatory sympathetic adrenergic fibers, while the pulmonary circulation has been described as less responsive to both nervous and humoral modulators. However, histochemical evidence has demonstrated the presence of adrenergic fibers in pulmonary circulation. Besides, reduced responsiveness is intriguing since the balance of regulation between systemic and pulmonary vascular circuits has critical hemodynamic implications in animals with an undivided ventricle and consequent cardiovascular shunts. The present study investigated the role and functional relevance of a and ll-adrenergic stimulation in regulating systemic and mainly the pulmonary circulations in a decerebrate, autonomically responsive rattlesnake preparation. The use of the decerebrate preparation allowed us to observe a new diverse functional modulation of vascular beds and the heart. In resting snakes, the pulmonary vasculature is less reactive to adrenergic agonists at 25 degrees C. However, the ll-adrenergic tone is relevant for modulating resting peripheral pulmonary conductance, while both a- and ll-adrenergic tones are relevant for the systemic circuit. Active dynamic modulation of both pulmonary compliance and conductance effectively counterbalances alterations in the systemic circulation to maintain the R-L shunt pattern. Furthermore, we suggest that despite the great attention given to cardiac adjustments, vascular modulation is sufficient to support the hemodynamic adjustments needed to control blood pressure. (AU)

• 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