BDNF and major depressive disorder: Current studies have shown that LPS is one of the classical modeling modalities for conducting depressive disease studies due to its pro-inflammatory effects by participating in numerous signaling pathways closely related to depression, such as the autophagic pathway (Ali et al., 2020) or the activation of inflammatory vesicles (Arioz et al., 2019) or tryptophan metabolism (Walker et al., 2019) or Trkb/BDNF signaling (Li et al., 2022b).