We have characterized the modulation of adenylyl cyclase (AC) activity by ligands of dopaminergic receptors in rat striatal homogenate and compared the results with receptor-ligand binding affinities. Despite the fact that rat striatum contains high level of both dopamine D(1) and D(2) receptors, only the D(1)-specific AC activation by agonists could be determined. All D(1)-receptor agonists (dopamine, dihydrexidine, and A 77636) used were able to increase cAMP accumulation in a concentration-dependent manner, while D(1)-receptor antagonists (SCH23390, SKF83566, and butaclamol) blocked the effects induced by the aforementioned agonists. At the same time, the D(2)-receptor agonist quinpirole and antagonist sulpiride had no effect on cAMP accumulation in striatal homogenate neither on the basal level nor on the activated level of AC, while inhibited [(3)H]raclopride binding to these membranes. Comparing the ligands of the D(1) receptor in modulating the activity of AC and displacing D(1)-receptor-specific radioligand [(3)H]SCH23390 binding revealed that the ligands modulate both of these processes with similar affinities. It indicates that under given experimental conditions, only dopamine D(1)-receptor-mediated stimulation of AC activity can be measured in membrane homogenate of rat striatum, while dopamine D(2)-receptor effects remain fully hidden.