INHIBITION BY THE TETRAMINE DISULPHIDE, BENEXTRAMINE, OF CARDIAC CHRONOTROPIC HISTAMINE H2‐RECEPTOR‐MEDIATED EFFECTS

1 Benextramine (N,N'‐bis[o‐methoxybenzylamino)‐n‐hexyl]cystamine), which irreversibly blocks α‐adrenoceptors and does not inhibit the H1‐receptor‐mediated contractile effect of histamine on guinea‐pig isolated ileum, also did not inhibit the H1‐receptor‐mediated inotropic effect of histamine on guinea‐pig isolated atrium. 2 Benextramine irreversibly inhibited the H2‐receptor‐mediated chronotropic effect of histamine on guinea‐pig isolated atrium. 3 Since its combination with the competitive H2‐receptor blocking drug cimetidine had an additive blocking effect, benextramine appears to act directly on the chronotropic H2‐receptor.