Potentiation by Alpha-Methyldopa of Pressor Responses to Angiotensin 1

Summary

Chronic treatment with methyldopa, for 4 to 7 days, produced augmentation of pressor responses to angiotensin in the denervated hindleg of dogs, whereas vasoconstrictor responses to norepinephrine were unaffected. The administration of a single iv injection of methyldopa did not alter the hindleg pressor responses to either angiotensin or norepinephrine. Since chronic treatment with methyldopa has been shown to decrease plasma renin activity in man, it is possible that the potentiation of the vasoconstrictor effect of angiotensin seen in dogs after chronic treatment with methyldopa may be related to an effect of this drug on the renin-angiotensin system.