Studies on the role of histamine and 5-hydroxytryptamine in immunity against the nematode Trichostrongylus colubriformis. IV. Inhibition of the expulsion of worms transplanted into the duodenum of immune guinea pigs.

Significant numbers of fourth larval stage Trichostrongylus colubriformis from sheep donors are expelled from the small intestine of T. colubriformis-immune guinea pigs within 8 h of transplantation into this organ. This model system for the immune expulsion of gastrointestinal nematode parasites was used in the current experiments to examine the effect of drugs recently shown to modify the release of histamine. The experiments showed that worm expulsion was inhibited by the beta-adrenergic agonists salbutamol and isoprenaline, the phosphodiesterase inhibitors aminophylline and ICI 63,197, the antiallergic drug ICI 74,917 and the antihistamine mepyramine. The beta-blocker propranolol prevented inhibition of worm expulsion following salbutamol treatment and there was some evidence of synergistic action between salbutamol and ICI 63,197. The results support previous findings suggesting an important role for histamine release in the effector mechanism of the immune response of guinea pigs against the parasitic nematode T.colubriformis.