Osthole Ameliorates Cognitive Impairment in Ovariectomized Rats via Estrogen-Mediated Enhancement of Cholinergic Function and Regulation of Neurotransmitter Homeostasis

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive dysfunction that is closely associated with cholinergic system damage. Estrogen deficiency is a well-established risk factor for AD in women. Osthole (OST), a phytoestrogen with mild, bidirectional regulatory properties, has been proposed as a potential estrogen replacement. This study aimed to investigate the mechanisms by which OST ameliorates cognitive impairment. Cognitive deficits were induced in female Sprague-Dawley rats by bilateral ovariectomy (OVX), and OST was subsequently administered by oral gavage. Behavioral tests revealed that OST significantly improved learning and memory and reduced anxiety-like and depression-like behaviors in OVX rats. H&E staining and Nissl staining demonstrated that OST reversed neuronal damage in the hippocampus and cortex. Western blotting, ELISA, and immunofluorescence staining indicated that OST treatment restored the estrogen–cholinergic–NGF axis: E 2 , ERα, and ERβ expression were upregulated; Ach, ChAT, NGF, and TrkA levels were increased, whereas AChE activity was decreased. Moreover, OST inhibited neuronal apoptosis by elevating Bcl-2 and reducing Bax expression, enhanced the expression of markers of synaptic plasticity (PSD95, SYN, and BDNF), and modulated neurotransmitter release (GABA and E). Collectively, these multi-target effects identify OST as a promising candidate for treating AD in women.