Schematic representation of the changes in the 5-HTergic neural pathways in mice after ovariectomy and the underlying mechanisms. 5-HT, 5-hydroxytryptamine; 5-HTIAA, 5-hydroxyindole acetic acid; 5-HT1AR, 5-HT1A receptor; 5-HT2AR, 5-HT2A receptor; E2, oestradiol; ERα, oestrogen receptor α; ERβ, oestrogen receptor β; GPR30, G-protein coupled receptor 30; TPH2, tryptophan hydroxylase; MAOA, monoamine oxidase A.