Postsynaptic dopamine DA1- and DA2-receptors in jejunal arteries of rabbits.

Changes in the external diameter of rabbit isolated jejunal arteries were measured by a photoelectric device. Both norepinephrine and dopamine produced vasoconstriction; prazosin, but not idazoxan, antagonized these effects. Arteries preconstricted with norepinephrine were dilated by SKF 38393 and LY 171555. SCH 23390 antagonized both compounds, however, in the case of LY 171555 with a lower potency. Sulpiride also interacted with LY 171555. When arteries were preconstricted with PGF2 alpha in the presence of prazosin, idazoxan, and propranolol, SKF 38393 caused vasodilation, while LY 171555 and dopamine were inactive. We conclude that in jejunal arteries both DA1- and DA2-receptors may be present at the vascular smooth muscle.