Interactions between opiate- and dopamine-induced effects on adenylate cyclase in rat striatum

In rat striatal P2 membrane preparations examined under constant experimental conditions, activation of either D2-dopamine or opiate receptors inhibited basal adenylate cyclase with a similar maximal inhibition of approximately 30%. These inhibitions were not additive. D1 dopamine receptor-mediated activation of adenylate cyclase by SKF38393 was inhibited by morphine in an additive fashion, but the opiate had minimal effects on the net activation of adenylate cyclase by dopamine which activates both D1 and D2 receptors. From these results it would appear that opiate and D1 dopamine receptor-mediated activation of adenylate cyclase summate, but that opiate and D2 dopamine receptors regulate a common pool of adenylate cyclase in striatal membranes.