The effects of atropine on anaphylactic shock in the guinea-pig.

The effects of atropine, 2 mg/kg i.v., on anaphylactic shock were studied in guinea-pigs sensitized to ovalbumin. Atropine only moderately reduced (--31%) the increase in pulmonary resistance observed and slightly prolonged (+26%) the survival time in pretreated animals compared with controls. These effects, however, were no statistically significant. The drug temporarily improved ventilation but had no influence on haematosis. On the other hand, atropine significantly reduced the amount of histamine released (--60%) and of GMPc synthetized in the lung (--21%). The levels of AMPc and prostaglandins E1, E2 and F2 alpha remained comparable to those of control animals. These results suggest that the reflex-induced action of the cholinergic system during anaphylaxis primarily affects large-calibre airways and that the role of acetylcholine in severe reactions is moderate when compared with the direct action of other mediators.