Choline acetyltransferase immunohistochemical staining. Representative photomicrographs of intraparenchimal Sap injection effects. Images show brain sections of rats that were saline-treated, sham-lesioned (a, b and c); saline-treated, Sap-lesioned (a1, b1 and c1); donepezil-treated, sham-lesioned (d, e and f); and donepezil-treated, Sap-lesioned (d1, e1 and f1). Coronal sections at the level of medial septum (a, a1, d and d1), nucleus basalis magnocellularis (b, b1, e and e1) and striatal (c, c1, f and f1) regions with choline acetyltransferase immunoreactive neurons are shown. Note the substantial absence of cholinergic neurons in both regions of the lesioned animal (a1, b1, d1 and e1) and the substantial preservation of striatal cholinergic interneurons (c1 and f1). Lens objective: 10×. Scale bars: 50 μm.