Migration of Hymenolepis diminuta (Cestoda) and changes in 5-HT (serotonin) levels in the rat host following parenteral and oral 5-HT administration.

Changes in the distribution of the tapeworm Hymenolepis diminuta in the rat small intestine were studied for up to 3 h following intraperitoneal, intramuscular, subcutaneous, and oral administration of 5-HT. Changes in 5-HT levels in the arterial circulation, intestinal lumen, and in worm tissue were also monitored. In all cases following 5-HT administration there was an anteriad migration by H. diminuta. The extent of the migration was dose dependent, the higher the dose the more marked the migration response. Normal 5-HT levels in the parasitized gut are higher than those in uninfected animals. The pattern of increasing levels of 5-HT in worm tissue directly followed the increases in the intestinal lumen, suggesting that worm 5-HT was of host origin. Blood 5-HT level similarly followed luminal increases. It is suggested that the pharmacological action of 5-HT on H. diminuta resulting in worm migration is implemented through the regulation of helminth neuromuscular activity and the carbohydrate metabolism, as has been demonstrated in other parasitic worms.