The purpose of this study was: (1) to investigate the distribution of H1- and H2- histaminergic receptors in the pulmonary artery and vein of the pig, and (2) to observe the hemodynamic and respiratory effects induced by 10 min of i.v. infusion of histamine in the anesthetized pig. D-chlorpheniramine and cimetidine were used as H1- and H2-receptor antagonists. Our results demonstrate a contractile response of the isolated pulmonary vein and artery (i.d. from 2.0 to 2.5 mm) which is mediated by H1-receptors. The i.v. infusion of histamine was followed by an early significant increase of heart rate (HR) and mean pulmonary artery pressure. Subsequently a significant fall of cardiac output (CO) and dynamic pulmonary compliance were observed in association with hypoxia and hemoconcentration. After d-chlorpheniramine the infusion of histamine induced a marked pulmonary and systemic vasodilatation, hypotension and an increase in HR and CO. These effects could be dependent on a direct stimulation of H2-receptors possibly present in the smallest pulmonary vessels. Most of the effects observed during the infusion of histamine alone persisted after cimetidine administration. Moreover an increase of the pulmonary dynamic compliance was observed during H1-receptor stimulation. The combined blockade of H1- and H2-receptors prevented all the described effects.
- Anesthetized pig
- H- and H-histamine receptors
- Histamine Pulmonary hemodynamics
- Isolated pulmonary vessels
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience