Induction of hyperphosphorylated tau in living slices of rat hippocampal formation and subsequent detection using an ELISA

Although hyperphosphorylated tau is an established feature of Alzheimer's D isease, its role in the disease process is poorly understood, partly becaus e of lack of suitable animal models. We describe the use of living slices o f rat hippocampal formation to study tau phosphorylation. Using the AT8 ant ibody in an ELISA, phosphorylated tau was detected in freshly frozen slices and it increased significantly in slices that were incubated in an electro physiological recording chamber; the amount detected was greatest when the homogenisation buffer contained phosphatase and kinase inhibitors. The phos phorylated tau content of the slices increased significantly after exposure to the phosphatase 1 and 2A inhibitor okadaic acid (OA) - 1.5 mu M. Electr ophysiological recordings confirmed that slices were alive and that OA had no acute toxic effect. In control slices phosphorylated tau, detected immun ohistochemically, was mainly in the somatodendritic compartment of neurones ; in OA treated slices, there was an apparent decrease in somatodendritic A T8 staining and an increase in neuropil staining. Our system enables the in duction of hyperhosphorylated tau within living slices, in an experimental environment that can be used to study the biological consequences of such a change, and may therefore help further our understanding of the significan ce of hyperphosphorylated tau in Alzheimer's Disease. (C) 1999 Elsevier Sci ence B.V. All rights reserved.