The Action of 5‐hydroxytryptamine on the Blood Vessels of the Human Hand and Forearm

Rapport, Green, and Page in 1948 isolated a vasoactive substance ("serotonin") from beef serum and this was later shown (Rapport, 1949) to, be 5-hydroxytryptamine, the creatinine sulphate (5- HT) of which has since been produced synthetically (Hamlin and Fischer, 1951 ; Specter, Heinzelmann, and Weisblat, 1951).The presence of 5-HT has been demonstrated in many body tissues and fluids of man and animals, including the alimentary canal (Dalgliesh, Toh, and Work, 1953), brain and urine (Twarog and Page, 1953), enterochromaffin tissue (Erspamer and Asero, 1952), blood serum (Erspamer and Sala, 1954) and platelets (Zucker and Borelli, 1955).It has been suggested that this substance plays a part in haemostasis (Zucker, 1947), in kidney function (Erspamer and Sala, 1954) and in central nervous activity (Stole, 1947).Its effects on the circulation suggest that it has a role in the regulation of vascular tone (Page, 1952).The mechanism of this last effect is still obscure and the present paper attempts to define the actions of 5-HT on peripheral blood vessels in man by observation of blood flow, heat loss and volume changes in the upper limb during local arterial injections.