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

Abstract

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