The copper-peroxide-silver method: a highly sensitive procedure for the demonstration of Alzheimer's disease lesions and for signal intensification in immunocytochemistry.

Abstract

Ammoniacal silver solutions give striking impregnation of Alzheimer's disease (AD) lesions if sections are pretreated with copper sulfate and hydrogen peroxide. In contrast to most silver impregnation methods, no staining of normal neurites is obtained, and senile plaques (SPs), neurofibrillary tangles (NFTs), and neuropil threads (NTs) are strongly stained in black against a clear background. A sodium acetate wash interposed between the copper sulfate and hydrogen peroxide resulted in suppression of the staining of amyloid lesions. This variant of the basic procedure (CPS-II method), maintains the capacity of the latter (CPS-I method) to strongly impregnate NFTs and NTs. In addition, it clearly delineates the dystrophic neurites of SPs obscured by the strong argyrophilia of the amyloid deposits seen in CPS-I stains. NTs are strongly impregnated with both CPS-I and CPS-II methods and are unmasked from normal neurites, which remain unstained. The staining can be abolished by pretreatment with formic acid and erased with a brief wash in sulfochromic acid. Destained sections can be restained with either method or with immunoperoxidase procedures. CPS staining of previously immunostained tissues produces marked intensification of the diaminobenzidine reaction product. In AD brains, the immunostaining is markedly enhanced and selective when the silver procedure is preceded by formic acid treatment. The selectivity and high sensitivity of the procedure may be useful as a diagnostic tool and of value to study the biogenesis and natural evolution of the brain lesions of AD.(ABSTRACT TRUNCATED AT 250 WORDS)