What is known about the action of dihydroergotamine on the vasculature in man?

The vasoconstrictor activity of dihydroergotamine is long-lasting and independent from continuously elevated plasma levels. There is evidence that dihydroergotamine accumulates at the vascular smooth muscle cells and elicits venoconstriction through both stimulation of 5-HT receptors as well as sensitization of the venous smooth muscle to the constrictor activity of biogenic amines. In vivo, the vasoconstrictor activity of dihydroergotamine is probably modulated through vasoactive metabolites, i.e., the vasoconstrictor profile and efficacy obviously varies with the ratio of the parent drug and dihydroergotamine metabolites in plasma.