After phenoxybenzamine (10-5M), pretreatment, and in the presence of propranolol (10-6M) and indomethacin (2.8 × 10-6M), dopamine caused a marked concentration-dependent relaxation of isolated strips of human basilar artery contracted with PGF2α. This effect was mimicked by apomorphine, 6,7-ADTN and SK&F 38393, but N,N-diethyl dopamine, N,N-di-n-propyl-dopamine and 5,6-ADTN caused only slight relaxation. (+)-Butaclamol, cis-α-flupenthixol, fluphenazine and haloperidol competitively antagonised the relaxant effects of dopamine, but sulpiride was ineffective in concentrations as high as 1.3 × 10-4M. These findings show that the dopamine receptors in the human basilar artery closely resemble those in the smooth muscle of the rabbit isolated mesenteric and splenic arteries, and the dog renal and mesenteric arteries in vivo, but differ from those located presynaptically on sympathetic nerve terminals. © 1983.
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