ACTION OF EBROTIDINE, RANITIDINE AND CIMETIDINE ON THE SPECIFIC BINDING TO HISTAMINE H-1-RECEPTOR AND H-2-RECEPTOR

Ebrotidine ethyl]amino]methylene]-4-bromo-benzenesulfonamide, CAS 1009 81-43-9, FI-3542), a selective H-2-receptor antagonist, has proved to competitively inhibit the positive chronotropism induced by histamine in isolated guinea pig atrium. The affinity of ebrotidine to histamine H-1- and H-2-receptors through the displacement of H-3-pyrilamine and H-3-thiotidine binding to guinea pig cerebellum and brain cortex memb ranes was investigated. Ebrotidine displaced H-3-thiotidine specific b inding to histamine H-2-receptors (K-i: 127.5 nmol/l), showing a highe r affinity (p < 0.05) than ranitidine (K-i: 190.0 nmol/l) and cimetidi ne (K-i: 246.1 nmol/l). None of the three substances displaced H-3-pyr ilamine binding to H-1-receptors (K-i: > 5000 nmol/l). The results sho wed that ebrotidine is a drug with a high affinity for H-2 receptors, higher than cimetidine and ranitidine.