[Experimental pharmacological studies of the venous tonus-modifying effect of dihydroergotamine].

In isolated human femoral veins, the dihydrogenated ergot alkaloid dihydroergotamine (DHE) produced an increase in tone at nanomolar concentrations. With regard to the onset and duration of action and reversibility, the DHE-induced contractions differed from those induced by noradrenaline and serotonin. In isolated femoral arteries examined for comparison DHE at comparatively high concentrations was much less effective. It is likely that the vasoconstrictor effect of DHE is due in part to its interaction with serotonin receptors and alpha-adrenoceptors. DHE as a partial agonist is able to antagonize the effects of serotonin and noradrenaline.