Neuroprotective effects of Shaoyao Gancao decoction against excitatory damage in PC12 cells based on the Src-NR2-nNOS pathway

Objective: To explore the neuroprotective effects of the Shaoyao Gancao decoction (SGD) against excitatory damage in PC12 cells and the role of the Src-NR2-nNOS pathway mediation by SGD in regulating γ-aminobutyric acid (GABA)-glutamate (Glu) homeostasis. Methods: N-Methyl-d-aspartic acid (NMDA) was used to establish a PC12 cell excitability injury model. To investigate the neuroprotective effect of SGD, a cell counting kit-8 (CCK-8) assay was used to determine PC12 cell viability, Annexin V/Propidium Iodide (Annexin V/PI) double staining was used to determine PC12 cell apoptosis, and Ca2+ concentration was observed using laser confocal microscopy. GABA receptor agonists and antagonists were used to analyze the neuroprotective interactions between γ-aminobutyric acid (GABA) and NMDA receptors. Additionally, molecular biology techniques were used to determine mRNA and protein expression in the Src-NR2-nNOS pathway. We analyzed the correlations between the regulatory sites of GABA and NMDA interactions, excitatory neurotoxicity, and brain damage at the molecular level. Results: NMDA excitotoxic injury manifested as a significant decrease in cell activity, increased apoptosis and caspase-3 protein expression, and a significant increase in intracellular Ca2+ concentration. Administration of SGD, a GABAA receptor agonist (muscimol), or a GABAB receptor agonist (baclofen) decreased intracellular Ca2+ concentrations, attenuated apoptosis, and reversed NMDA-induced upregulation of caspase-3, Src, NMDAR2A, NMDAR2B, and nNOS. Unexpectedly, a GABAA receptor antagonist (bicuculline) and a GABAB receptor antagonist (saclofen) failed to significantly increase excitatory neurotoxicity. Conclusions: Taken together, these results not only provide an experimental basis for SGD administration in the clinical treatment of central nervous system injury diseases, but also suggest that the Src-NR2A-nNOS pathway may be a valuable target in excitotoxicity treatment.