Abstract
Dopamine receptors (DRs) are generally considered as mediators of vasomotor functions. However, when used in pharmacological studies, dopamine and/or DR agonists may not discriminate among different DR subtypes and may even stimulate alpha1 and beta-adrenoceptors. Here, we tested the hypothesis that D2R and/or D3R may specifically induce vasoconstriction in isolated mouse aorta. Aorta, isolated from wild-type (WT) and D3R(-)/(-) mice, was mounted in a wire myograph and challenged with cumulative concentrations of phenylephrine (PE), acetylcholine (ACh), and the D3R agonist 7-hydrxy-N,N-dipropyl-2-aminotetralin (7-OH-DPAT), with or without the D2R antagonist L741,626 and the D3R antagonist SB-277011-A. The vasoconstriction to PE and the vasodilatation to ACh were not different in WT and D3R(-)/(-); in contrast, the contractile responses to 7-OH-DPAT were significantly weaker in D3R(-)/(-), though not abolished. L741,626 did not change the contractile response induced by 7-OH-DPAT in WT or in D3R(-)/(-), whereas SB-277011-A significantly reduced it in WT but did not in D3R(-)/(-). D3R mRNA (assessed by qPCR) was about 5-fold more abundant than D2R mRNA in aorta from WT and undetectable in aorta from D3R(-)/(-). Following transduction with lentivirus (72-h incubation) delivering synthetic microRNAs to specifically inactivate D2R (LV-miR-D2) or D3R (LV-miR-D3), the contractile response to 7-OH-DPAT was unaffected by LV-miR-D2, while it was significantly reduced by LV-miR-D3. These data indicate that, at least in mouse aorta, D3R stimulation induces vasoconstriction, while D2R stimulation does not. This is consistent with the higher expression level of D3R. The residual vasoconstriction elicited by high concentration D3R agonist in D3R(-)/(-) and/or in the presence of D3R antagonist is likely to be unrelated to DRs.