Changes in tissue and intestinal serotonin (5-HT) levels in the laboratory rat following feeding and the effect of 5-HT inhibitors on the migratory response of Hymenolepis diminuta (Cestoda)

Abstract

Following withdrawal of food for 24 h, rats infected with ten 11-day-old Hymenolepis diminuta were given, via stomach tube, either 2 mL water, 1.2 mmol MgSO4 in 2 mL water, 1.2 × 10−3 mmol methysergide hydrogenmaleinate in 2 mL water, or 1.2 × 10−2 mmol methysergide in 2 mL water. Thirty minutes after treatment rats were again given access to food. In untreated control animals and in two further experimental groups which received either 2 mL water or 1.2 × 10−2 mmol methysergide in 2 mL water, food continued to be withheld after treatment.The amount of food ingested was determined, as well as changes in mucosal, luminal, and worm serotonin (5-HT) levels. Changes in worm biomass distribution were also monitored. The addition of the specific 5-HT antagonist methysergide resulted in over a 90% inhibition in worm migratory response; MgSO4 resulted in 67% inhibition indicating a direct relationship between intestinal 5-HT levels and the distribution and the migratory behaviour of H. diminuta within the intestinal lumen.