Involvement of serotonin in intestinal mastocytopoiesis and inflammation during a Trichinella spiralis infection in mice.

The involvement of serotonin in the regulation of intestinal mastocytopoiesis and inflammation has been investigated in mice infected with Trichinella spiralis. Two serotonin antagonists, methysergide and ketanserin, were examined for their ability to interfere with jejunal pathology comprising the influx of mucosal mast cells and other inflammatory cells during an infection with T. spiralis and with worm expulsion. In vitro analysis of the frequency of mast cell precursors in bone marrow, blood, spleen and intestinal tissue suggested that the mucosal mast cell response during a T. spiralis infection is probably due to invasion and local maturation in the gut of mast cell precursors, and may be mediated by T-cell-derived mast cell growth factors. Since both serotonin antagonists inhibited the mucosal mast cell response in T. spiralis-infected mice and diminished the influx of eosinophilic granulocytes, goblet cell hyperplasia, and villous atrophy, it was concluded that during a T. spiralis infection in mice release of serotonin may provide an environment that facilitates the local influx in the gut of inflammatory cells. Since worm expulsion was not affected by the serotonin antagonists, these results suggest that worm expulsion can occur without a mast cell and or eosinophilic granulocyte influx. The role of serotonin release by as yet unidentified serotonin-containing cells in the gut in relation with T cell regulation is discussed.