Effect of histamine and its antagonists on the course of Nippostrongylus brasiliensis in rats

Abstract

The involvement of histamine in the rejection of Nippostrongylus brasiliensis (nematode) from rats harbouring 18 to 20-day-old infections was investigated. Parenteral administration of histamine delayed worm rejection. A similar effect was observed with histamine depletor, compound 48/80, and the prostaglandin synthesis inhibitor indomethacin. Antihistaminics, mepyramine and pyribenzamine failed to alter the course of infection, and neither did the histamine synthesis inhibitor, semicarbazide. Pretreatment of rats with the H₁, histamine receptor antagonist, mepyramine, effectively antagonized histamine-induced worm retention, whereas the H₂ histamine receptor antagonist cimetidine had a negligible effect. The results suggest that histamine or histamine depletors do not have any apparent role in self-cure mechanism; rather they support parasitism.