1 This study was designed to investigate the involvement of postjunctional D 2 -like receptors in a rabbit vasculature model used to evaluate the D 1 -like agonist activity. Dopamine, epinine and (7)-DP-5,6-ADTN, three mixed D 1 /D 2 -like agonists, fenoldopam and SKF 82958, two selective D 1 -like agonists and SKF 89124, a selective D 2 -like agonist, were administered cumulatively in precontracted and a/b-blocked rabbit splenic artery rings in order to evaluate their D 1 -like-mediated vasorelaxant activity before and after pretreatment with the selective D 2 -like antagonist YM 09151-2 (1 nM). 2 Dopamine (pD 2 =6.35+0.09), epinine (pD 2 =6.73+0.13), (7)-DP-5,6-ADTN (pD 2 =7.56+0.09) and SKF 82958 (pD 2 =8.55+0.10) reversed completely the U46619-induced contracture whereas SKF 89124 was inactive up to 10 mM and fenoldopam acted like a partial agonist (pD 2 =8.31+0.09, a=0.62). The selective D 2 -like dopamine receptor antagonist YM 09151-2 (1 nM) signi®cantly (P50.05) potentiated the vasorelaxant activity of dopamine (pD 2 =7.01+0.07), epinine (pD 2 =7.14+0.08), (7)-DP-5,6-ADTN (pD 2 =8.19+0.09) and SKF 89124 (40% relaxation at 10 mM), whereas it did not alter the e ects of fenoldopam (pD 2 =8.40+0.09, a=0.68) and SKF 82958 (pD 2 =8.58+0.08). 3 The D 2 -like antagonist YM 09151-2 induced the same degree of e ect with all the substances tested in both endothelium-denuded and endothelium-intact preparations. 4 The selective D 2 -like dopamine receptor agonist SKF 89124 did not produce any intrinsic e ect on the splenic artery, but was able to produce a rightward shift of the forskolin-induced relaxation. 5 The results of these experiments support the existence of a non-endothelial postjunctional D 2 -like dopamine receptor counteracting the D 1 -like-mediated vasodilatation in rabbit splenic artery, probably by the inhibition of adenylate cyclase.