NPY and Alzheimer disease: The immunohistochemistry examinations showed that TH, NPY, GAP43 (P < 0.01) and PGP9.5 (P < 0.05) expressions were significantly up‐regulated in AV group (vs S group), GAP43 was down‐regulated in AD group (vs AV group) (P < 0.01) in the RV (Figure 1C).