Serotonin in Trichinella pseudospiralis: An immunocytochemical study

This is the first report on the presence and localization of the neurotransmitter serotonin (5-HT) in the nervous system of the nematode Trichinella pseudospiralis, the causative agent of trichinellosis. The orientation of the 5-HT-immunoreactive (5-HT-IR) nerve cells in the adult worm is described. In the anterior region of the worm 5-HT-IR occurs in 7 neurons. Longitudinal nerve cords extend posteriorly from the anterior end. They are connected by transverse commissures. The vulval area is intensively supplied with 5-HT-IR nerve cells and fibres forming a plexus. Two rows of small 5HT-IR structures, hypodermal glands, are visible along the whole nematode body. Because of the conserved structural features among nematodes the 5-HT-IR neurons observed are likely to have counterparts in the model worm, Caenorhabditis elegans. Some basic differences are evident and demand further study.