Astragaloside IV ameliorates cognitive impairment after traumatic brain injury with involvement of NMDAR-related signaling

Traumatic brain injury (TBI) can cause persistent cognitive impairment accompanied by neuronal and synaptic damage. Astragaloside IV (AS-IV) has neuroprotective properties, but the signaling processes associated with its effects after TBI remain incompletely understood. Adult male mice underwent controlled cortical impact and received intraperitoneal AS-IV during a 28-day post-injury period, with GM1 included as a positive control. Behavioral assessments, immunofluorescence, Golgi-Cox staining, transmission electron microscopy, and immunoblotting were combined with NMDAR antagonist co-treatment and exploratory docking, molecular dynamics, and cellular thermal shift analyses. AS-IV treatment improved cognitive performance and was associated with preservation of dendritic and synaptic structure, increased NMDAR subunit expression, and changes in ERK1/2, CaMKII, and CREB phosphorylation and synapse-associated proteins. The 40 mg/kg dose showed greater effects than 80 mg/kg for several outcomes. Co-treatment with MK-801 or TCN-201 attenuated multiple AS-IV-associated effects, supporting involvement of NMDAR-related signaling. Computational predictions and NMDAR2A thermal stabilization were consistent with possible receptor engagement but did not establish direct binding, binding affinity, or receptor activation. Collectively, these findings suggest that modulation of NMDAR-related signaling alterations may contribute to the cognitive and synaptic structural and molecular effects associated with AS-IV after TBI. However, the present data do not establish direct NMDAR binding or activation, in vivo target occupancy, or NMDAR as the exclusive or primary molecular target of AS-IV.