STUDIES ON THE NONSPECIFIC BLOCKING ACTION OF BENZYLTRIMETHYLAMMONIUM BROMIDE (BTM)

¹ Departments of Pharmacology and Physiology, College of Medicine, University of Iowa, Iowa City, Iowa

The blocking action of benzyltrimethylammonium bromide (BTM) was investigated on the superfused guinea-pig ileum with the agonists acetylcholine, histamine and potassium chloride. The low doses of the agonists were blocked to a greater degree than the higher doses. In the presence of atropine, BTM still blocked the responses to potassium chloride. By doubling the potassium in the bathing solution the action of BTM could be abolished. On the rat uterus BTM blocked the responses to acetylcholine and serotonin in a manner similar to the ileum. BTM decreased the membrane resistance in the isolated frog skin and gastric mucosa. On the mucosa it blocked the effect of acetylcholine. The drug reduced the nerve compound action potential only in high concentrations but at normal blocking concentrations it caused a rubidium-86 efflux from the nerve. The blocking action of BTM is thought to be related to a decrease in membrane resistance accompanied by an efflux of potassium.