Effect of histamine, serotonin, and acetylcholine on the peripheral airways.

Abstract

Injection of histamine into the right side of the heart of paralyzed, vagotomized, artificially ventilated cats increased transpulmonary pressure swing ([DELTA]PTP) within 3 sec, expelled air from the lungs, decreased pulmonary compliance (CL) and increased pulmonary resistance (RL), without decreasing anatomic dead space (Vd). Air expulsion and the decrease in CL were related aad independent of the increase in RL. Left heart injections produced delayed and smaller changes. Histological studies made after histamine injection and rapid freezing of the lungs showed constriction of respiratory bronchioles and alveolar ducts (peripheral airway constriction). Right heart injection of serotonin and acetylcholine increased RL more and decreased CL less than histamine, and they decreased Vd, suggesting constriction of conducting airways (bronchoconstriction) as well as peripheral airway constriction. With right heart injection of histamine, serotonin, and acetylcholine in dogs, [DELTA]PTP increased prior to constriction of a bypassed tracheal segment. The results show that constriction of the peripheral airways produces characteristic changes that are different from bronchoconstriction.