Studies on the Role of Histamine and 5-Hydroxytryptamine in Immunity against the Nematode Trichostrongylus colubriformis

Infusion of solutions of histamine and 5-hydroxytryptamine into the small intestine of guinea pigs during the fourth larval stage of a primary infection with the nematode Trichostrongylus colubriformis led to significant worm expulsion. Incubation of fourth stage larvae with 5-hydroxytryptamine significantly reduced their excretion of the metabolic end product propionic acid. These results support the hypothesis that histamine and 5-hydroxytryptamine are involved in the expulsion of T.colubriformis by immune guinea pigs.