Aim: To investigate the in vivo induction of Alzheimer-like tau phosphorylation by wortmannin and the attenuation by melatonin.
Methods: Stereotaxic technique was used for administrating wortmannin or melatonin into rat lateral ventricle. The phosphorylation of tau was analyzed by immunocytochemistry and Western blot, and ultrastructural alteration in neuronal processes was detected by electron microscopy.
Results: Level of phosphorylated tau at paired helical filament-1 (PHF-1) epitope was elevated at 1 h, peaked at 6 h, and then decreased at 12 h and 24 h after injection of wortmannin 10 mumol/L. The increased tau phosphorylation at particular epitope determined at 6 h was arrested by preinjection of melatonin 10 mumol/L or 100 mumol/L for 12 h. The wortmannin-induced hyperphosphorylation of tau was mainly detected in pyramidal neuron of hippocampus, and swelled axons and depredated myelin sheaths were also seen in the same region of the brain.
Conclusion: Wortmannin induced in vivo Alzheimer-like hyperphosphorylation of tau at Ser396/404, and melatonin inhibited partially the pathological processes.