Subcurative doses of the antischistosomal drug tris (p-aminophenyl) carbonium chloride (TAC) to mice infected with Schistosoma mansoni produce three distinct changes in the parasite:
1.A reduction of glycogen in the cuticular tubercles of the males. This is followed by a flattening and subsequent disappearance of these structures.
2.Alterations in the morphologic and functional properties of the female reproductive system detectable by an intra vitam staining method and leading to abnormal egg formation. In contrast to the former two changes, the effects on the female reproductive system are not specific for TAC, but are observed also after administration of subcurative doses of other antischistosomal drugs.
3.At a later stage, inhibition of acetylcholinesterase activity in the nervous system of the worm resulting in a paralysis of the adhesive organs. This coincides with the separation of the sexual pairs and a shift of the worms from the mesenteric vessels toward the liver. The drug-induced paralysis of the adhesive organs is reversed immediately on exposure of the worms to cholinergic-blocking agents in vitro.