Absence of [3H]SCH 23390 binding sites in the rat adrenal gland

The binding of D2-dopamine receptor ligand [3H]spiperone and selective D1-ligand [3H]SCH 23390 to the rat adrenal gland and striatum has been compared. [3H]Spiperone showed specific binding in both tissues revealing a Bmax of 887 fmol mg-1 protein and KD of 0.38 nM, and B of 34 fmol mg-1 protein and KD of 0.66 nM in the striatum and adrenal gland, respectively. On the other hand, [3H]SCH 23390 showed a specific binding to the striatal tissue with Bmax of 747 fmol mg-1 protein and KD of 0.70 nM, while in the adrenal tissue no specific binding was observed. These results apparently indicated only D2-dopamine receptor binding sites being present in the rat adrenal gland.