Furthermore, metformin has been shown to mitigate synaptic plasticity damage induced by LPS in rats (Zhou et al., 2021) and improve the expression of synaptic plasticity markers [anti-microtubule-associated protein 2, synaptophysin (SYP), postsynaptic density protein 95], thereby alleviating depressive-like behavior in mice with allergic rhinitis (AR) (Lv et al., 2023). The gene discussed is SYP; the disease is allergic rhinitis.