Research Paper Volume 17, Issue 3 pp 822—850

Figure 7. Effect of quercetin (4) on histochemical staining of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Representative photomicrographs of histochemical staining of AChE (A–D) and BChE (E–H). Staining at pH 6.8 demonstrates AChE- (A) and BChE (E)-associated plaques in the Alzheimer’s disease (AD) orbitofrontal cortex (arrows). Staining at pH 8.0 demonstrates AChE (C) and BChE (G) associated with normal neural structures in the AD thalamus (arrowheads showing neurons). Staining reactions for AChE and BChE at pH 6.8 (B and F) or pH 8.0 (D and H) in the presence of quercetin (4) could not be done due to compound 4 precipitating out of solution, most likely due to chelating with metal ions required for the Karnovsky-Roots (KR) staining method. Note, for ease of reference, identical images of the positive control staining of AChE and BChE at pH 6.8 and 8.0 (A, C, E, G) were used herein and in Figures 4–6, 8, 9 (A, C, E, G) to help compare directly the effects of each senolytic or nootropic agent on the standard BChE KR histochemical staining method. Abbreviations: OFC, orbitofrontal cortex; VA, ventroanterior thalamic nucleus; WM, white matter. Scale bar = 500 μm.