PTGS2 and major depressive disorder: Our results are in keeping with previous studies of Song et al. [61] who, using the 5-week CMS and LPS challenge to model depression in Wistar rats, reported elevated production of COX-2 and PGE2 in dendritic spines [35,101], in the CA1 area and dentate gyrus of the hippocampus, which were associated with decreased dendritic plasticity, oxidative stress, and depressive-like behaviors [61].