Mannotriose regulates learning and memory signal transduction in the hippocampus

Rehmannia is a commonly used Chinese herb, which improves ieaming and memory. However, the crucial components of the signal transduction pathway associated with this effect remain elusive. Pri- mary hippocampal neurons were cultured in vitro, insulted with high-concentration （1 × 10-4 mol/L） cor- ticosterone, and treated with 1 × 104 mol/L mannotriose. Thiazolyl blue tetrazolium bromide assay and western blot analysis showed that hippocampal neuron survival rates and protein levels of glucocorti- cold receptor, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor were all dramatically decreased after high-concentration corticosterone-induced injury. This effect was reversed by mannotriose, to a similar level as RU38486 and donepezil. Our findings indicate that mannotriose could protect hippocampal neurons from high-concentration corticosterone-induced injury. The mechanism by which this occurred was associated with levels of glucocorticoid receptor protein, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor.