Agonist-induced subsensitivity of adenylate cyclase coupled with a dopamine receptor in slices from rat corpus striatum.

Incubation, for 30 min, of striatal slices with 10 microM dopamine, 10 microM apomorphine, or 10 microM SKF 38393 decreased dopamine-stimulated adenylate cyclase activity by 50-60%. This loss in dopamine-stimulated enzyme activity appears to be mediated by a persistent occupancy of recognition sites of the D-1 receptor because: (i) at 10 microM, SKF 38393, a selective D-1 receptor agonist, facilitates desensitization and Ly 141865, a selective D-2 receptor agonist, fails to elicit desensitization of dopamine-dependent adenylate cyclase; and (ii) preincubation with dopamine in the presence of 1 microM haloperidol but not 1 microM sulpiride curtails the desensitization of dopamine-dependent adenylate cyclase. In dopamine-desensitized striatal slices of the Kd for N-propylnorapomorphine binding is increased but the content of membrane-bound calmodulin and the activation of adenylate cyclase by NaF and cholera toxin are decreased significantly. In striatal slices incubated with dopamine for prolonged time periods the coupling of the GTP-binding protein with adenylate cyclase and dopamine recognition sites may be impaired and the content of membrane-bound calmodulin is decreased.