Hypotensive effect induced by a cyclic dopamine analog,...

The antihypertensive effects of trans-4-methyl-7,8-dihydroxy-1,2,3,4,4a,5,6,10b-octahydrobenzo[f]quinoline, a dopamine agonist, were investigated in dogs and spontaneous hypertensive rats. Intravenous administration of low doses of this cyclic analog of dopamine (0.25--1.00 microgram/kg) consistently reduced blood pressure and heart rate, concurrently recorded in the dog. This effect was antagonized by haloperidol, a specific dopamine antagonist. The dopamine analog also reduced systolic blood pressure of spontaneous hypertensive rats. This study confirmed the possibility that the decrease in blood pressure and heart rate elicited by the dopamine analog is attributable to an effect on specific dopaminergic receptors.