The adrenergic regulation of the cardiovascular system in the South American rattlesnake, Crotalus durissus.
The present study investigates adrenergic regulation of the systemic and pulmonary circulations of the anaesthetised South American rattlesnake, Crotalus durissus. Haemodynamic measurements were made following bolus injections of adrenaline and adrenergic antagonists administered through a systemic arterial catheter. Adrenaline caused a marked systemic vasoconstriction that was abolished by phentolamine, indicating this response was mediated through alpha-adrenergic receptors. Injection of phentolamine gave rise to a pronounced vasodilatation (systemic conductance (G(sys)) more than doubled), while injection of propranolol caused a systemic vasoconstriction, pointing to a potent alpha-adrenergic, and a weaker beta-adrenergic tone in the systemic vasculature of Crotalus. Overall, the pulmonary vasculature was far less responsive to adrenergic stimulation than the systemic circulation. Adrenaline caused a small but non-significant pulmonary vasodilatation and there was tendency of reducing this dilatation after either phentolamine or propranolol. Injection of phentolamine increased pulmonary conductance (G(pul)), while injection of propranolol produced a small pulmonary constriction, indicating that alpha-adrenergic and beta-adrenergic receptors contribute to a basal regulation of the pulmonary vasculature. Our results suggest adrenergic regulation of the systemic vasculature, rather than the pulmonary, may be an important factor in the development of intracardiac shunts.
Galli
Gina L J
GL
Zoophysiology, Department of Biological Sciences, University of Aarhus, Building 1131, 8000 Aarhus C, Denmark. ginaljgalli@hotmail.com
Skovgaard
Nini
N
Abe
Augusto S
AS
Taylor
Edwin W
EW
Wang
Tobias
T
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism; D001794:Blood Pressure; D002319:Cardiovascular System / Q000187:drug effects / Q000378:metabolism*; D017839:Crotalus / Q000378:metabolism*; D004837:Epinephrine / Q000378:metabolism*; D006339:Heart Rate; D007269:Injections, Intra-Arterial; D010646:Phentolamine / Q000008:administration & dosage; D011433:Propranolol / Q000008:administration & dosage; D011651:Pulmonary Artery / Q000378:metabolism; D011652:Pulmonary Circulation; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012039:Regional Blood Flow; D012107:Research Design; D013318:Stroke Volume; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D004837:Epinephrine; D010646:Phentolamine