Javi, try stimulating them with thrombin and use CD62P ( MA1-81632 Pierce). 

Rodrigo 

Hi Rodrigo

Thanks for your answer. I had already thought to use CD62P, but I need to also use other marked. Other option is VASP, but I want to use a marker for IIb/IIIa activation in rat. Do you konw any?

Regards and thanks

Javi

What about Fibrinogen Binding Assay?

When GPIIb/IIa activated, it bind to fibrinogen.

Search Fibrinogen Binding assay in PUBMED, you can find many papers.

Javi, try stimulating them with TRAP (Trombine activater recepror factor). TRAP - specific agonist of IIb/IIIa receprots.

Hi Javier , we used JON/A from Emfret analytics and it worked good in our hands. 

Hi, Javier  

I also suggest as Preeti that  you can try with JON/A

(It best for mouse, but i don't use in rat)

Others receptor or information, you also can see attached picture (From the book: Platelet and Megakaryocytes)

Wish this informations can help you

I agree with Yao-Wen we used this ab in mouse platelets, some CD61 antibodies are which you use with rat platelets are available at ebioscience

http://www.ebioscience.com/catalogsearch/result/?q=CD61&order=name_sort&dir=asc