title: Enhanced depressive-like behaviors after Toll-like receptor 7 stimulation in mice.
abstract: Toll-like receptor (TLR) 7 recognizes viral single-stranded RNA and triggers anti-viral immune responses through the production of type I interferons (IFNs) IFN-alpha and IFN-beta. IFN-alpha is known to induce various psychiatric changes such as depressive symptoms; however, the correlation with TLR7 activation remains to be determined. In this study, we examined the effect of imiquimod, a TLR7 specific ligand, on depressive-like behaviors evaluated by the forced swim test (FST) and the tail suspension test (TST) in mice. Immobility durations were significantly prolonged in both FST and TST by 2 h after imiquimod treatment (50 microg/body, i.p.), indicating that TLR7 activation enhanced depressive-like behaviors in mice. In addition, imiquimod induced IFN-alpha mRNA expression in the hippocampus, whereas it prevented long-term potentiation in the Schaffer-CA1 pathway (i.e., hippocampal synaptic plasticity). Moreover, TLR7 mRNA expression in the hippocampus was higher than that in the whole brain. These findings suggest that TLR7 activation enhances depressive-like behaviors in mice, possibly through increasing IFN-alpha expression and altering synaptic plasticity in the hippocampus.
authors: Yasunori
authors: Y
authors: Kubo
authors: Yoshiki
authors: Y
authors: Yanagawa
authors: Machiko
authors: M
authors: Matsumoto
authors: Sachiko
authors: S
authors: Hiraide
authors: Hiroko
authors: H
authors: Togashi
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D016207:Cytokines / Q000378:metabolism; D003863:Depression / Q000378:metabolism*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000077271:Imiquimod; D007369:Interferon Inducers / Q000494:pharmacology*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D051199:Toll-Like Receptor 7 / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D016207:Cytokines; D007369:Interferon Inducers; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; D000077271:Imiquimod