Microglia participate in postoperative cognitive dysfunction by mediating the loss of inhibitory synapse through the complement pathway

•Exploring the pathogenesis of postoperative cognitive dysfunction is essential to improve the prognosis of patients.•The establishment of POCD model in aged mice and related behavioral experiments are more relevant to clinical treatment and have more clinical significance.•The combination of neuroinflammation caused by microglia and complement pathway plays an important role in the destruction of neural network leading to cognitive dysfunction.•The E/I imbalance mediated by the loss of inhibitory synapses is a new mechanism and discovery that leads to cognitive dysfunction.•This finding provides an idea for future research on whether neurons with inhibitory function can be regulated to improve cognitive function.