Immunohistochemical analysis of modified forms of Aβ in aging Tg2576 brain. Serial sections (5 μm) of Tg2576 cerebral cortex were labeled with anti-N1(D), anti-N1(iD), anti-N1(rD), anti-N3(pE), and 4G8. The age of the mouse brain analyzed is shown at the top of each set of serial sections. Scale bar, 17 μm.