The role of the prostanoid system in mediating the haemodynamic effects of dihydroergotamine.

Dihydroergotamine (DHE) increases tonus in veins, especially in capacitance vessels, thereby reducing blood pooling and increasing venous blood flow velocity and it has been suggested that DHE achieves its effect partially through its influence on prostanoids synthesis and release. Pretreatment with indomethacin did not affect DHE response in central haemodynamic variables or in tissue blood flow in dogs; nor did it affect the reduced venous vessel area, increased blood flow in dogs; nor did it affect the reduced venous vessel area, increased venous blood flow velocity (measured ultrasonically), or reduced resting calf volume blood flow (measured by plethysmography), caused by DHE in humans. Although the number of animals and of humans in this study were small, nontheless it seems unlikely that the effect of clinically relevant doses of DHE is appreciably mediated by the prostanoid system.