Examinations on contribution of bradykinin in the action of dopamine in circulatory system of rats. II. Influence of bradykinin in the action of dopamine on the vessel perfusion of the isolated hindpaw of rats.

The influence of different doses of bradykinin (0.1 micrograms, 1.0 micrograms/0.1 ml) and dopamine (0.1, 0.25, 0.5 micrograms/0.1 ml) on the flow through vessels of the isolated hindpaw of rat was estimated. Dopamine in small doses did not change and in the highest doses decreased the vascular flow. Bradykinin decreased the vascular flow and the effect was dose-dependent. This peptide administered together with dopamine in the smallest dose, evoked the same effect as dopamine itself in the highest dose and decreased the effect of dopamine introduced into the organism in the highest dose. Administration of phentolamine and propranolol decreased the vascular flow. The vasodilating effect of dopamine was seen after administration of drugs blocking the adrenergic receptors and the vaso-constricting effect of dopamine administered in the highest dose was not observed. Bradykinin decreased the vascular flow and when administered together with dopamine evoked effect similar to that after administration of the peptide with phentolamine and propranolol. The authors suppose that except the modifying influence of bradykinin on the action of dopamine, the role of the peptide receptor in this action cannot be excluded.