Influence of Acetylcholine and Biogenic Amines on Branchial, Pulmonary and Systemic Vascular Resistance in the African Lungfish, Protopterus Aethiopicus

The effects of acetylcholine and biogenic amines on the main vascular beds in lungfish were studied in intact animals and in isolated preparations perfused with physiological solution. Acetylcholine, histamine and serotonin increased the branchial as well as the pulmonary and the systemic vascular resistance. The sensitivity to acetylcholine was highest in the branchial blood vessels. Adrenaline and noradrenaline caused increased resistance in pulmonary and systemic blood vessels, whereas the branchial vascular bed usually responded by dilatation. The results are discussed in relation to the vascular responses obtained with the same pharmacological agents in other species of fish.