Dopamine and L-dopa potentiation of pressor responses to norepinephrine in isolated perfused rat kidneys.
The ability of l-dopa and dopamine to modulate renal vascular responses to norepinephrine (NE, 50-150 ng) was examined in isolated Tyrode-perfused kidneys from male Sprague-Dawley rats. Renal pressor responses to bolus injections of NE were constant during saline infusion. In contrast, l-dopa (15 micrograms/min and 75 micrograms/min) and dopamine (15 micrograms/min) infusions that did not alter baseline perfusion pressure increased pressor responses to NE significantly. Concomitant infusion of the aromatic l-amino-acid decarboxylase inhibitor carbidopa (20 micrograms/min) suppressed the ability of l-dopa (75 micrograms/min) but not dopamine to enhance renal pressor responses to NE. The pressor potentiation of NE did not appear to be the result of a general musculotropic effect or altered alpha-1 adrenoreceptor activity since increased vasoconstrictor responses to phenylephrine (PE) and serotonin (5-HT) were not observed. Infusions of cocaine (15 micrograms/min) enhanced the renal pressor effects of NE but not PE in similar fashion to l-dopa and dopamine. In the presence of cocaine, l-dopa did not potentiate NE constriction further. These results suggest that endogenous or exogenous dopamine in the kidney may affect neuronal NE uptake to enhance its renal vascular effects.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002230:Carbidopa / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology* / Q000652:urine; D004357:Drug Synergism; D007668:Kidney / Q000098:blood supply* / Q000378:metabolism; D007980:Levodopa / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
D007980:Levodopa; D003042:Cocaine; D002230:Carbidopa; D004298:Dopamine; D009638:Norepinephrine