Inhibition of dopamine-activated adenylate cyclase and dopamine binding by opiate receptors in rat striatum.

Low-affinity (micromolar) 3H-dopamine binding was measured under conditions which permitted dopamine activation and opiate inhibition of adenylate cyclase in rat striatal membranes. Opiate drugs and peptides inhibited the dopamine binding in the presence of both GTP and Gpp(NH)p. Opiate inhibition of adenylate cyclase was, however, observed only in the presence of GTP. It is suggested that the dopamine D1 receptor in striatum may be modulated by the opiate delta receptor through a shared guanine nucleotide binding subunit.