AIM To study the effects of long-term application of dopamine HCl (DA) on the functional changes of dopamine receptor subtypes coupled to adenyl cyclase in rat renal cortex. METHODS cAMP levels were measured by radioimmunoassay as an index of dopamine receptor function. RESULTS Injection of DA (30 mg.kg-1.d-1, i.p. 30 d) reduced the fenoldopam (Fen) (100 mumol.L-1)-induced increments of cAMP production from the control group of +1.26 +/- 0.04 to the DA-treated group of +0.63 +/- 0.22 nmol.min-1/g tissue and the propyl-butyl-dopamine (PBDA) (100 mumol.L-1)-induced decrements of cAMP production in the presence of Sch-23390 (Sch) from the control group of -0.38 +/- 0.18 to the DA-treated group of -0.11 +/- 0.08 nmol.min-1/g tissue with, however, comparable percentile changes for the 2 groups. Sch blocked both Fen- and PBDA-induced increase in cAMP production, while domperidone (Dom) blocked the decreasing effects of PBDA on cAMP accumulation in the presence of Sch. CONCLUSION Long-term application of DA produced a marked "down regulation" of both DA1 and DA2 receptors in rat renal cortex with, however, the responsiveness of the remaining receptors unchanged.