Liquiritigenin (LQ), a flavonoid extracted from the radix of Glycyrrhiza, has anti-inflammatory and neuroprotective properties. In this study, we evaluated the cognitive enhancing effects of LQ on learning and memory impairments induced by scopolamine (0.5 mg/kg, i.p.), a muscarinic antagonist, using the Y-maze, passive avoidance, and novel object recognition tests. A single administration of LQ significantly improved scopolamine-induced cognitive impairments in these behavioral tests. In addition, LQ dramatically inhibited acetylcholinesterase and thiobarbituric acid reactive substance activities in the hippocampus of scopolamine-induced mice in a dose-dependent manner. Furthermore, LQ markedly increased the protein level of brain-derived neurotrophic factor (BDNF) and phosphorylation of extracellular signal-regulated kinase (ERK) and cAMP response element binding (CREB) in the hippocampus of scopolamine-induced mice. Taken together, our results indicate that LQ may be useful for the treatment of learning and memory impairments, and that the beneficial effects of LQ are mediated, in part, by cholinergic and BDNF/ERK/CREB signaling enhancement and/or protection.
Keywords: Alzheimer’s disease; Brain-derived neurotrophic factor; Extracellular signal-regulated kinase; Liquiritigenin; Scopolamine; cAMP response element binding.