Synaptic Plasticity-Enhancing and Cognitive-Improving Effects of Standardized Ethanol Extract of Perilla frutescens var. acuta in a Scopolamine-Induced Mouse Model

In our previous study, we demonstrated that a standardized ethanol extract of Perilla frutescens var. acuta (PE) alleviates memory deficits in an Alzheimer's disease mouse model by inhibiting amyloid β (Aβ) aggregation and promoting its disaggregation. However, the extent to which PE exerts additional cognitive benefits independent of Aβ pathology remained unclear. Here, we aimed to evaluate the effects of PE on synaptic plasticity and learning and memory functions. Male ICR mice were used, and cognitive impairment was induced by scopolamine administration. PE was orally administered at doses determined from previous studies, and cognitive performance was assessed using the passive avoidance, Y-maze, and Morris water maze tests. In parallel, hippocampal slices were employed to examine the effects of PE on synaptic plasticity. PE (100 and 300 μg/mL) significantly enhanced long-term potentiation (LTP) in a concentration-dependent manner without altering basal synaptic transmission. This facilitation of LTP was blocked by scopolamine (1 μM), a muscarinic acetylcholine receptor (mAChR) antagonist, and IEM-1460 (50 μM), a calcium-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (CP-AMPAR) inhibitor, indicating the involvement of mAChR and CP-AMPAR pathways. In vivo, PE (100, 250, and 500 mg/kg) treatment improved memory performance across all behavioral tasks and upregulated hippocampal synaptic proteins including GluN2B, PSD-95, and CaMKII. Collectively, these results demonstrate that PE ameliorates scopolamine (1 mg/kg)-induced cognitive impairment by enhancing synaptic plasticity, likely through modulation of mAChR, CP-AMPAR, and NMDA receptor signaling. These findings highlight the therapeutic potential of PE for memory deficits associated with cholinergic dysfunction.