Dopamine D1-like receptor subtypes in human peripheral blood lymphocytes

Molecular biology studies have shown that human peripheral blood lymphocyte s express a dopamine D5 receptor, whereas no information is available on do pamine DI receptor, the other dopamine D1-like receptor subtype. Radioligan d binding assay investigations with the nonsubtype selective dopamine D1-li ke receptor antagonist [H-3]SCH 23390 as radioligand have suggested the pre sence of a dopamine D5 receptor in human peripheral blood lymphocytes. Howe ver. so far no evidence was provided as whether or not human peripheral blo od lymphocytes express a dopamine D1 receptor. In this study, we have inves tigated dopamine D1 and D5 receptor mRNA and the influence of antibodies ag ainst dopamine D1 and D5 receptors on [H-3]SCH 23390 binding to intact huma n peripheral blood lymphocytes. The two receptors were also analyzed by imm unocytochemistry. Dopamine D5 receptor, but not D1 mRNA, was detected in hu man peripheral blood lymphocytes. Anti-dopamine D5 receptor antibodies, but not anti-dopamine D1 receptor antibodies, significantly decreased [H-3]SCH 23390 binding to human peripheral blood lymphocytes. A dark-brown immunore activity was visualized in cytospin centrifuged human peripheral blood lymp hocytes exposed to anti-dopamine D5, but not to anti-dopamine D1 receptor a ntibodies. These data collectively indicate that dopamine D5 receptor is th e only dopamine D1-like receptor subtype expressed by human peripheral bloo d lymphocytes. (C) 1999 Elsevier Science. All rights reserved.