The antagonism of the vascular effects of 5-hydroxytryptamine by BOL 148 and sodium salicylate in the human subject.

2-Bromo-(+)-lysergic acid diethylamide (BOL 148) is a specific antagonist of the constrictor response of the forearm and hand blood vessels to intra-arterial infusions of 5-hydroxytryptamine. This has been shown to be a direct action in the tissue concerned, since the antagonism was as effective when the drug was given by local arterial injection as when given intravenously. Sodium salicylate is also a specific antagonist of 5-hydroxytryptamine, but its action is indirect, occurring only when the general serum level was raised above 10 or 20 mg.%; local limb concentrations of 30 to 40 mg.% had no antagonistic effect. The mechanism of the antagonistic effect of salicylate is not known. It is not related to the associated hyperventilation but is possibly due to the secondary release of, or synergism with, some other substance, probably a hormone.