NO.18 The New Function of Serotonin and Melatonin: Specific Biocide for Chlamydiae in Vitro

Intracellular tryptophan depletion by IFN-γis one of the most important host defense systems against chiamydial infection, when it is not enough, resulting in leading chiamydial growth to persistent state. That is why chiamydial IFN-γresistance and host/tissue tropism are thought to depend on the divergence of chiamydial tryptophan operon. As in the examination with tryptophan and its derivatives, serotonin and melatonin showed remarkable reduction of chiamydial infection. Moreover, an inhibitor of G protein, pertussis toxin, restricts the melatonin action but not serotonin, indicating the involvement of G-protein coupled receptors in melatonin function. Besides the well-known neural functions for maintenance of organism homeostasis, this is the first report for antichlamydial function of serotonin and melatonin.