Immunohistochemistry staining of p-CREB in murine brains. Mice were orally preadministrated with tacrine (2 mg/kg), ursolic acid (2 mg/kg), ODH (100 or 200 mg/kg) for four weeks and injected with scopolamine (3 mg/kg) to induce amnesia. Dissected brain was cut into coronal frozen sections (4 μm) and stained with BDNF antibody. The sections of hippocampus region were photographed at ×100 magnification. The expression of p-CREB was observed in hippocampus of mice (arrows). N: normal group, C: control group, P: tacrine treated positive control groups, U: ursolic acid treated groups, O100: ODH 100 mg/kg treated group, O200: ODH 200 mg/kg treated group.