Evidence for different 5-HT(1B/1D) receptors mediating vasoconstriction of equine digital arteries and veins

Abstract

5-hydroxytryptamine (5-HT) is a potent vasoconstrictor of equine digital arteries and veins which may play a role in the ischaemic disease, laminitis. The present investigation compared the properties of 5-HT(1B/1D) receptors in arteries with those in veins using isolated rings of equine digital blood vessels. The 5-HT(1B/1D) receptor-selective agonists, anpirtoline and sumatriptan were 17.9 and 10 times more potent and produced 4.1 and 5.6 times greater maximum contractions, respectively, in veins when compared to arteries. Other agonists tested were of equal potency and produced the same maximum responses in veins and arteries. Propranolol competitively inhibited 5-HT(1B/1D) receptor media..