Intracerebroventricular siAAH impairs cerebellar development. Cerebella of rats treated by intracerebroventricular injections of siAAH, siScr, pAAH, or pGFP were harvested on P21, sectioned in the mid-sagittal plane, fixed in Histochoice, and embedded in paraffin. Histological sections were stained with LHE. (A-C) Low (100×) and (D-F) high (600×) magnification images of cerebella from (A, D) siScr, (B, E) siAAH, or (C, F) pAAH injected rats. Note long, thin, regular folia with well-developed, slender white matter (wm) cores, compact and densely populated granule (gcl) and Purkinje (PC) cell layers in cerebella of siScr- and pAAH-transfected rats, compared with the more shallow, blunted, broad, and irregular folia, thick white matter cores, irregular thickness of the granule cell layer, and neuronal loss or neuronal atrophy in the Purkinje cell layer (arrows) in cerebella of siAAH-transfected rats. (C) Cerebella of pAAH-transfected rats displayed only subtle differences from siScr or pGFP (not shown) controls in that the granule cell layer was somewhat less linear due to slightly increased architectural complexity (C; arrows). The molecular layer (ml) of the cerebella were similar in all groups.