Dopamine receptors in human platelets

The expression of dopamine receptors by human platelets was investigated by Western blot analysis and immunocytochemical techniques using antibodies raised against dopamine D1-D5 receptor protein. The influence of dopamine D1-like and D2-like receptor agonists on adrenaline-induced platelet aggregation was also investigated. Western blot analysis revealed that platelet membranes bind anti-dopamine D3 or D5 receptor protein antibodies, but not anti-D1, D2 or D4 receptor protein antibodies. Cytospin centrifuged human platelets exposed to anti-dopamine D3 or D5 receptor protein antibodies developed a specific immune staining, whereas no positive staining was noticeable in platelets exposed to other antibodies tested. Both the D1-like receptor agonist 1-phenyl2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol hydrochloride (SKF 38393) and the D2-like receptor agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) dose-dependently inhibited adrenaline-induced platelet aggregation. These effects were decreased respectively by the D-like and D2-like receptor antagonists R(+)-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol hydrochloride (SCH 23390) and (-)sulpiride. The above findings indicate that human platelets express dopamine D3 and D5 receptors probably involved in the regulation of platelet function.