EFFECTS OF DOPAMINE ON VEINS IN HUMANS - COMPARISON WITH NORADRENALINE AND INFLUENCE OF AGE

Objective: To compare the venoconstricting effect of dopamine with tha t of noradrenaline and to investigate the influence of age on the resp onsiveness to dopamine in human subjects. Methods: In eight young and eight elderly male subjects, increasing doses of dopamine or noradrena line were infused into a dorsal hand vein and its diameter was measure d using a linear variable differential transformer. Results: There was no significant difference between the maximum venoconstriction (E-max ) for dopamine and that for noradrenaline. The infusion rate to induce 50% of E-max (ED50) for dopamine in the young and elderly subjects wa s 363 ng.min(-1) and 352 ng.min(-1), and the ED50 for noradrenaline wa s 40.7 ng.min(-1) and 43.8 ng.min(-1), respectively. Neither in the E- max nor in the ED50 for these drugs were there significant differences between the young and elderly subjects. Conclusion: The venoconstrict ing effect of dopamine is 5-20 times less than that of noradrenaline, and aging does not influence the responsiveness to dopamine and noradr enaline in human subjects.