In order to validate the use of [3H]mepyramine as a radioligand to label airway histamine H1 receptors, the results of radioligand binding experiments using porcine tracheal tissue membranes were compared with the results of physiologic studies measuring histamine-induced trachealis muscle contraction. Close agreement was found between histamine-induced [3H]mepyramine binding inhibition and histamine concentration-contraction-response curves. Close agreement was also found between the KD of mepyramine-induced [3H]mepyramine binding inhibition and the K beta of mepyramine antagonism of muscle contractions stimulated by 10(-4) M histamine. [3H]Mepyramine binding was found to be rapid, reversible, saturable and stereospecific. Only H1 agonists and antagonists displayed potent [3H]mepyramine binding inhibition in competition binding studies. The results fulfill criteria for histamine H1 receptor identification by radioligand binding with [3H]mepyramine.
Aminopyridines Animals