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

Cardiovascular Effects of Intravenous Infusions of 5‐hydroxytryptamine in Man

“…When it is infused into the brachial artery at a constant rate of 1 to 16 [tg./min. the blood flow through the forearm, after an initial transient dilatation, is reduced, indicating a constriction of arterioles (Roddie et al, 1955); the capacity vessels, probably mainly the veins and venules, show an increase in their tone (Glover, Greenfield, Kidd, and Whelan, 1958); the capillaries are dilated as evidenced by the flushing of the skin, and, with larger doses, there is an increase in limb volume suggesting an increased capillary permeability and oedema formation (Roddie et al, 1955).…”

“…5-Hydroxytryptamine has been shown to be a powerful vasoconstrictor substance, and its direct action on the smooth muscle of blood vessels has been demonstrated in isolated preparations, in animals and in man (Reid and Rand, 1951 ;Page, 1942;Reid, 1952;Roddie, Shepherd and Whelan, 1955). However, intra-arterial injection of 5-hydroxytryptamine into a limb, although it leduces the total blood flow, results also in a flushing of the skin, indicating dilatation of small vessels; a similar flushing is seen in patients with carcinoid tumours when large amounts of 5-hydroxytryptamine are circulating in the blood stream (Roddie et al, 1955;Thorson, Biorck, Bjorkman, and Waldenstrom, 1954). Furthermore, the variability of the blood pressure change; seen on intravenous infusions of 5-hydroxytryptamine (Page and McCubbin, 1953) suggests that it does not behave as a general overall vasoconstrictor substance.…”

Antagonism by Methysergide of Vascular Effects of 5‐hydroxytryptamine in Man

“…Red flushing of forearm skin was observed and prickling sensations were often experienced. These changes were similar to those described by Roddie et al (1955). The infused arm was then treated with methysergide (25 u1g/min for 10 min) and doses of 5-HT were repeated.…”

“…The normal vasoconstrictor response (Roddie et al, 1955) was replaced by a significant dilatation in 4 subjects (as in O.C., Fig. 3) and greatly reduced in 2 subjects (as in J.R., Fig.…”

“…The vascular responses in the upper limbs of normal human subjects to intra-arterially administered 5-hydroxytryptamine (5HT) were described by Roddie, Shepherd & Whelan (1955) and by Bock, Dengler, Khun & Matthes (1957). Glover, Marshall & Whelan (1957) found the lysergic acid derivative 2-bromo-(-+)-lysergic acid diethylamide bitartrate (BOL 148) to be a specific antagonist of the constrictor response of forearm and hand blood vessels to intra-arterial infusions of 5-HT.…”