In line with previous studies, our results showed that catalpol can upregulate BDNF level and here existed the strong positive correlation between the ACh level and the BDNF level in the hippocampus (r = 0.859, P < 0.01), which are together beneficial to memory improvement and to explain from another side why catalpol ameliorated memory impairments in the SCOP-induced amnesic mice. Here, BDNF is linked to memory impairment.