Intra-arterial infusion of [¹²⁵I]Aβ1-40 labels amyloid deposits in the aged primate brain in vivo

Alzheimer's disease is characterized by extracellular amyloid deposits in the brain at both vascular sites (cerebrovascular amyloid, CVA) and within the neuropil (plaques). In the present study we demonstrated that brain amyloid of aged non-human primates is efficiently detected by [¹²⁵I]Aβ in vitro, and assessed the detection of that amyloid in vivo by intravascular infusion of [¹²⁵I]Aβ. Aged squirrel monkeys (Saimiri sciureus) were anesthetized and infused intra-arterially with [¹²⁵I]Aβ, and sacrificed 2 h later. Analysis of the anterior frontal and temporal cortices by autoradiography demonstrated that [¹²⁵I]Aβ was deposited on CVA and that essentially every amyloid deposit which could be detected with thioflavin S or anti-Aβ antibodies was also labeled by [¹²⁵I]Aβ. These experiments suggest that intravascular infusion of radiolabeled Aβ can be used to detect and image amyloid deposits in the human AD brain.