Immunolocalization of NMDAR1 on megakaryocytes. (A) Cryosection of rat bone indicating intense NMDAR1 immunoreactivity (brown reaction product) on bone marrow megakaryocytes (arrows). (B) Antibody control, hematoxylin counterstain. Positive immunostaining was also identified on human megakaryocytes (C, arrow), human platelets (D, arrows), and MEG-01 cells (E). (F and G) Colocalization studies showed that cells displaying NMDAR1 immunofluorescence in rat bone marrow (F, arrow) were acetylcholinesterase-positive (G, arrow). (H) MEG-01 cells demonstrated strong immunostaining for the glutamate transporter, GLAST. (I) MEG-01 antibody control. Original magnification: A and B, ×250; C, D, and E, ×1,000; F and G, ×500; H and I, ×200. Fig 3. Binding of the specific NMDA channel blocker, MK-801 to megakaryocytes in vivo. Autoradiography studies localized 3H-MK-801, identified as numerous black silver particles (A, arrows) to NMDAR1-positive (brown staining) megakaryocytes in rat ulna cryosections. Ligand binding was displaced by excess cold MK-801 (B). Original magnification × 1,000.
