INVESTIGATIONS INTO MECHANISM OF RESPIRATORY EFFECTS OF ANAPHYLATOXIN

The influence of various drugs on anaphylatoxin-induced bronchoconstriction and respiratory stimulation has been investigated in guinea pigs. 1. Urethane anaesthesia protects from the lethal outcome of even high doses of AT, although qualitatively the effects remain unchanged. 2. Acetyl salicylic acid inhibits the bronchoconstriction. 3. Furthermore, atropine as well as methysergide reduce the bronchoconstriction, but do not block it, nor do they prevent the lethality of high doses of AT. 4. Pretreatment of guinea pigs with tripelennamine combined with atropin prevents any bronchoconstriction after injection of AT, an effect that is not obtained with tripelennamine alone. 5. The tachypnoic effect of AT is not affected by anaesthesia or by pretreatment with atropine, tripelennamine, methysergide, acetylsalicylic acid or endoanaesthesia. It is however abolished after bilateral vagotomy. 6. It is concluded that AT is probably a general liberator of biogenic amines. The bronchospasm appears to be brought about not only by liberated histamine but also by 5-hydroxytryptamine and cholinergic stimulation. The tachypnoic effect of AT is caused by a reflex mechanism, the afferent pathway of which runs in the vagus nerve. The receptors are yet unknown, they seem to be situated in the lung and are different from those receptors which mediate the tachypnoea induced by histamine, veratrine and bradykinin. © 1968 Springer-Verlag.