Lack of adrenergic control of dorsal aortic blood pressure in the resting eel, Anguilla australis

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Abstract
Dorsal aortic and cardinal venous blood pressures, dorsal aortic blood flow, and heart rate were measured in different combinations in conscious unrestrained eels (Anguilla australis). One group of animals was treated with either bretylium (10 mg.kg−1) or saline vehicle and dorsal aortic blood pressure and heart rate were monitored for the next 6 days. Two other groups were treated with phentolamine (5 mg.kg−1) and either dorsal aortic blood pressure and heart rate, or dorsal aortic blood flow and venous pressure monitored for 6 hr. In vivo treatment with either bretylium of phentolamine produced effective blockade of the α‐adrenoceptor‐mediated vasoconstriction of stimulated saline‐perfused trunk preparations; however, neither drug had no lasting effects on arterial blood pressure. In addition, phentolamine had no lasting effects on venous blood pressures or dorsal aortic blood flow. It is concluded that, in the resting eel, systemic vascular resistance is not normally under adrenergic control.