Actions of Anaphylatoxin on Circulation and Respiration of the Guinea Pig

Abstract

A purified preparation of anaphylatoxin was investigated in spontaneously breathing guinea pigs, anesthetized generally or locally. The blood pressure, respiratory air flow and pleural pressure was recorded. The predominant action is to cause bronchospasm, which is partly elicited by histamine liberation and partly by a probably direct effect. The bronchoconstrictor effect is preceded by a period of tachypnea. It leads to lung inflation which may be followed by reflex apnea. A biphasic effect was observed on the circulation: a fall in blood pressure followed by a rise. Only some of the actions of anaphylatoxin cause tachyphylaxis, namely the direct and indirect bronchoconstrictor effects and the hypertensive action. The tachypnea and fall in blood pressure can be elicited repeatedly without reduction of responses.