Standardized extract of Ginkgo biloba induced memory consolidation in female mice with hypofunction of vesicular acetylcholine transporter

Abstract

Basal forebrain cholinergic neurons are pivotal for cholinergic signaling in the neocortex and hippocampal formation, crucially implicated in neurodegenerative diseases like late-onset Alzheimer's disease (LOAD), recognition memory impairments, and decision-making. The acetylcholine transporter (VAChT) is essential for loading acetylcholine into synaptic vesicles. Building on our previous findings showing that Ginkgo biloba extract (EGb) preserves recognition memory, we hypothesized EGb would enhance memory in female mice with varying VAChT reductions. We also explored whether reduced cholinergic signaling induces anxiety-like behavior and whether EGb could alleviate such symptoms. Three-month-old female mice with severe VAChT reduction (knockdown homozygotes; VAChT KD^HOM), moderate reduction (heterozygotes; VAChT KD^HET), and wild-type (WT) mice received the vehicle, 5 mg/kg Donepezil, or EGb at doses of 250, 500, and 1000 mg/kg for 30 days. Memory assessments included aversive tasks like discriminative avoidance memory and non-aversive tasks like object recognition and location memory. We assessed VAChT protein expression in the hippocampal formation (HF) using Western blotting and quantified VAChT-immunopositive cells (IR⁺) in specific HF subfields (dCA1, dCA3, dDG) using immunohistochemistry. Chronic EGb treatment significantly improved long-term memory in female VAChT KD^HOM mice in object recognition and locations memories in a dose-dependent manner, unlike Donepezil. Enhanced memory was correlated with an increase in VAChT-IR⁺ cells in the dCA1 of VAChT KD^HOM mice. Additionally, EGb reduced VAChT-IR⁺ cells in the dDG of VAChT KD^HET mice, which was associated with decreased anxiety-like behavior. These findings suggest that EGb effectively mitigates deficits caused by cholinergic deficiency in hippocampal-dependent memory consolidation, thereby improving our understanding of its role in modulating long-term memory and hippocampal plasticity.