Abstract
Many investigators have reported that the effect of dopamine on the peripheral vasculature apparently varies and is dependent on the species. Holtz and Credner (1) observed that dopamine produced depressor effects in blood pressure of guinea pigs and rabbits while pressor effects were produced in cats and dogs. In the anesthetized cat and dog, dopamine causes vasodilatations in the superior and inferior mesenteric, gastric, and renal arteries and vasoconstrictions in the hepatic and splenic arteries (2, 3).
Ebel (3) reported that the action of dopamine on the systemic blood pressure was the result of balance between these vasoconstrictions and vasodilatations. It is also reported that dopamine has a direct sympathomimetic action on the heart (2, 4-7), while some reports suggest that dopamine acts on the sympathetic nerve terminals since its effect is reduced by reserpine, cocaine (8) and ephedrine (9). On the other hand, Tsai (10) observed that dopamine has both actions on cat nictitating membrane and on guinea pig heart.
In order to analyse the pressor effect of dopamine in the rat, experiments herein were designed to study (a) the modification of dose-response curve of dopamine on the rat blood pressure by several drugs and (b) the local vasculature effects of dopamine at the hind limb and kidney.
