Differential effect of mu, delta, and kappa opioid agonists on adenylate cyclase activity.

D-Ala2, D-Leu5-enkephalin (DADLE) and dynorphin1-13 (Dyn1-13) inhibited striatal adenylate cyclase activity, both basal and dopamine-stimulated (DA), in rats and guinea pigs. The kappa-agonists bremazocine (BRZ), U-50,488 (trans-3,4-dicloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide), and U-69,593 (5 alpha, 7 alpha 8 beta)-(-)-N-methyl-N-(7-(1-pyrrolidinyl-1-oxaspiro (4.5)dec-8yl) benzeneacetamide inhibited only the basal adenylate cyclase activity, and such an effect was restricted to guinea pig striatum, an area known to contain a high density of kappa-binding sites. Moreover, BRZ was found to antagonize the inhibitory effect of both DADLE and Dyn1-13 in rat striatum.