Effects of dopamine receptor agonists on the cAMP content in arteries of the rabbit.

Effects of selective dopamine-1 (DA(1)) receptor agonist fenoldopam and dopamine-2 (DA(2)) receptor agonist propy1-butyl-dopamine (PBDA) on the cAMP generation system in renal, pulmonary, mesenteric and femoral arteries of rabbits were studied. The results are as follows. (1) Fenoldopam increased the cAMP production in a dose-dependent manner in pulmonary, renal and mesenteric arteries. This effect of fenoldopam was markedly blocked by specific DA(1) receptor antagonist SCH23390, but not at all by specific DA(2) receptor antagonist domperidone. (2) PBDA induced a dose-dependent decrease in cAMP content in femoral artery. However, the antagonist also moderately increased a dose-dependent cAMP production in mesenteric, pulmonary, and renal arteries. (3) Domperidone significantly decreased the inhibitory effect of PBDA on cAMP production in femoral artery, while it stimulated cAMP production in mesenteric artery but was of no effect on that in renal and pulmonary arteries. (4) SCH23390 had no effect on the inhibitory action of PBDA in decreasing cAMP content in femoral artery, while it markedly decreased the stimulatory action of PBDA on cAMP production in renal, pulmonary and mesenteric arteries. These findings suggest the presence of DA(1) receptors mediating the cAMP generation system in renal, pulmonary and mesenteric arteries, but only DA(2) receptors in femoral artery, and both DA1 and DA(2) receptors in mesenteric artery. PBDA inhibits the AC activity via stimulation of DA(2) receptors and increases the AC activity via stimulation of DA(1) receptors.