Characteristics of the dopamine receptors in the rabbit isolate splenic artery

After blockade of alpha- and beta-adrenoceptors, the tension induced by PGF2alpha in splenic artery strips was relaxed by dopamine, 6, 7-ADTN, N-methyldopamine, apomorphine, N, N-di-n-propyl 5, 6-ADTN, N, N-di-n-propyl 6, 7-ADTN and Sandoz 27-403; their equipotent concentrations (relative to dopamine = 1) were 0.2: 0.3: 0.4: 1.1: 3.9 and 3.9 respectively. 5, 6 ADTN, N-methyl 5,6ADTN, N, N-diethyldopamine, N, N-di-n-propyldopamine and SKF 38393 were weakly active or inactive at relaxing the splenic artery strip. Bulbocapnine and cis-alpha-flupenthixol were specific, competitive, reversible antagonists of dopamine. Fluphenazine, clozapine, trifluoperazine, haloperidol and spiroperidol also antagonised dopamine, but were relatively weak antagonists and a small part of their action was non-specific. Sulpiride was inactive against dopamine. SKF 38393 selectively antagonised the effects of dopamine demonstrating that SKF 38393 has affinity, but little efficacy at the dopamine receptors in the splenic artery. The findings with both agonists and antagonists suggest that the vascular dopamine receptors in the rabbit splenic artery resemble those in the dog renal and mesenteric vascular beds.