Sumatripan and 5-benzyloxytryptamine: contractility of two 5-HT 1D receptor ligands in canine saphenous veins

Abstract

Sumatripan and 5-benzyloxytryptamine are ligands with high affinity for 5-HT 1D receptors in the caudate nucleus. Both compounds contracted canine saphenous veins, in vitro. Benzyloxytryptamine was less potent as a contractile agonist than sumatriptan which was less potent than serotonin. In high concentrations (>10 −5 M) serotonin-induced contraction resulted, in part, from activation of α-adrenoceptors as determined by blockade of contraction with prazosin (10 −6 M) and idazoxan (10 −6 M). Likewise, benzyloxytryptamine but not sumatripan also activated contractile α-receptors in the canine saphenous vein. Furthermore, benzyloxytryptamine antagonized contraction to sumatriptan in an apparently non-competitive fashion. Thus, benzyloxytryptamine, although possessing some α-receptor agonist activity, like sumatriptan, can interact with serotonin receptors in canine saphenous veins. Although effects of sumatriptan and benzyloxytryptamine quantitatively differed in canine saphenous veins, both agents showed similar affinity and agonist efficacy at 5-HT 1D receptors in brain. These studies may reflect potential differences between the 5-HT 1D receptor in brain and the 5-HT 1-like receptor in canine saphenous veins.