Employing video-enhanced contrast (VEC) microscopy, we examined whether TAK-029 (GPIIb/IIIa antagonist) inhibits the adhesion of activated platelets to human brain microvascular endothelial cells (HBEC) in vitro. HBECs were cultured on a coverglass and put in the observation chamber of VEC microscopy. Then, activated platelets by adenosine diphosphate (ADP) (2 microM) were perfused over HBEC at a low shear rate of 10 s(-1) for 30 min and washed out. Platelets adhered directly to HBEC. However, platelet adhesion to HBEC was suppressed when platelet rich plasma with ADP (2 microM) plus TAK-029 (GPIIb/IIIa antagonist; 1 microM) was perfused over HBEC for 30 min and washed out. Anti-GPIbalpha antibody (GUR20-5) did not inhibit adhesion of ADP-activated platelets to HBEC. The above results showed adhesion of ADP-activated platelets to HBEC under flow in vitro is mediated via GPIIb/IIIa