Antagonism by some ergot derivatives of 5-HT-induced vasoconstriction

The ability of a number of ergot derivatives to inhibit 5-hydroxytryptamine (5-HT)-induced vasoconstriction was examined in the perfused rat mesenteric artery preparation. 5-HT produced an increase in perfusion pressure indicative of vasoconstriction. The ergot derivatives inhibited the 5-HT-induced vasoconstriction in a manner that was predominantly not competitive in nature. As 5-HT2 antagonists the ergot derivatives ranged in potency from CQ 32-084 which abolished the 5-HT2 receptor mediated response at a concentration of 10 nM to LY-141865 which was inactive up to a concentration of 10 microM.