CHOLINOCEPTOR ACTIVATION SUBSERVING THE EFFECTS OF INTERFERON-GAMMA ON THE CONTRACTILITY OF RAT ILEUM

RECOMBINANT rat interferon gamma stimulated the contractility of isola ted rat ileum at doses of 4-12 units/ml. Muscarinic cholinoceptors wer e involved, as treatment of the tissue with atropine prevented the con tractile response of the ileum. Furthermore, interferon gamma increase d the affinity of carbachol for the cholinoceptors and did not change its maximum effect. Neurogenic pathways were also involved since pretr eatment of ileum with hexamethonium, hemicholinium or tetrodotoxin imp aired the contractile effect of interferon gamma. In contrast to the a ction of exogenous carbachol, the effects of interferon gamma are indi rect. They appear to involve a G protein regulating phosphoinositide t urnover and cytoskeletal structures since they could not be induced in ileum strips that were pretreated with pertussis toxin, phospholipase C inhibitors (2-nitro-carboxyphenyl, NN-diphenyl carbamate and neomyc in), cytochalasine B or colchicine.