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 H. diminuta in the rat small intestine were studied for up to 3 h following i.p., i.m., s.c. and oral administration of 5-HT [hydroxytryptamine]. Changes in 5-HT levels in the arterial circulation, intestinal lumen and in worm tissue were 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 levels similarly followed luminal increases. Possibly, the pharmacological action of 5-HT on H. diminuta resulting in worm migration is implemented through the regulation of helminth neuromuscular activity and carbohydrate metabolism, as has been demonstrated in other parasitic worms.