Loganin improves learning and memory impairments induced by scopolamine in mice.

Loganin is an iridoid glycoside found in the Flos lonicerae, Fruit cornus, and Strychonos nux vomica. We investigated the effect of loganin on learning and memory impairments induced by scopolamine (0.5mg/kg, i.p.), a muscarinic antagonist, using the Y-maze, passive avoidance, and the Morris water maze tests in mice. In the Y-maze test, loganin (40 mg/kg, p.o.) significantly improved the scopolamine-induced memory impairment. In addition, loganin (20 and 40 mg/kg, p.o.) significantly reversed scopolamine-induced impairments measured by the passive avoidance and the Morris water maze tests. A day after the last trial session of the Morris water maze test (probe trial session), loganin (20 and 40 mg/kg) dose-dependently increased the latency time in the target quadrant. Furthermore, loganin significantly inhibited acetylcholinesterase activity in the hippocampus and frontal cortex. Loganin may have anti-amnesic activity that may hold significant therapeutic value in alleviating certain memory impairments observed in Alzheimer's disease.