Serotonin (5-Hydroxytryptamine) in trematodes

This article presents a review of own and published data on current state of research on the widespread in the animal kingdom neurotransmitter, serotonin (5-Hydroxytryptamine, 5-HT) in parasitic flatworms, trematodes. Parasitizing in various organs and tissues of humans and animals, representatives of this class of parasitic flatworms are causative agents of dangerous diseases that bring a great harm to a human health and large economic losses in agriculture. The nervous system of trematodes is well developed and regulate various vital functions of parasites. The review provides an analysis of the available data on the presence, localization and functional significance of serotonin in trematodes, its biosynthesis, metabolism and the interaction with their receptors. The relationships between the parasite and host were also discussed. The review contains tables with the list of adult and larval stages of trematodes studied so far in this regard, as well as the parthenogenetic generations of worms, in which tissues serotonin was identified. Micrographs illustrating the presence of serotonin-immunopositive nerve structures are also provided. The information issued in this manuscript will help to determine the ways and prospects for further researches in this field and search of the suitable targets for the directed action of antiparasitic drugs.