THE EFFECTS OF H1‐ AND H2‐RECEPTOR AGONISTS AND ANTAGONISTS ON TOTAL LUNG RESISTANCE, DYNAMIC LUNG COMPLIANCE AND IRRITANT RECEPTOR DISCHARGE IN THE ANAESTHETIZED DOG

Abstract

1 The effects of histamine and 4 methylhistamine (i.v.) alone, and in the presence of chlorpheniramine or cimetidine, on total lung resistance (R_L), dynamic lung compliance (C_dyn) and irritant receptor activity have been studied in dogs anaesthetized with chloralose. 2 Histamine produced dose-related increases in R_L and irritant receptor activity with associated falls in C_dyn which were blocked by chlorpheniramine but unaffected by cimetidine. 3 4 Methylhistamine produced small insignificant changes in R₁ and C_dyn and small significant increases in irritant receptor activity which were reduced with chlorpheniramine but unaffected by cimetidine. 4 The results suggest that histamine increases irritant receptor activity, either directly or indirectly, via H₁-receptors.