CHARACTERIZATION OF SUBSTANCE P‐INDUCED BRONCHOCONSTRICTION IN THE GUINEA‐PIG: A COMPARISON WITH ACETYLCHOLINE

Abstract

1. Substance P (0.5‐8.0 μg/kg, i.v.) induced bronchoconstriction in anaesthetized, mechanically‐ventilated guinea‐pigs, comprising increases in airways resistance and decreases in dynamic compliance. 2. These bronchoconstrictor responses were unaffected by bilateral vagotomy, pretreatment with pheniramine (2 mg/kg, i.v.) or by pretreatment with atropine (100 μg/kg, i.v.). Acetylcholine‐induced (4‐32 μg/kg, i.v.) bronchoconstriction was prevented by atropine pretreatment, whereas bilateral vagotomy inhibited responses to acetylcholine. 3. Ganglionic blockade using hexamethonium (20 mg/kg, i.v.) potentiated both substance P and acetylcholine on airways resistance and dynamic compliance. 4. Ind..