Abstract

The blocking action of benzyltrimethylammonium bromide (BTM) was studied with various nicotinic preparations. On the superfused frog rectus abdominis muscle preparations the compound blocked responses to acetylcholine, nicotine and KCl. Doubling the potassium in the bathing solution negated the BTM effect. BTM caused inhibition of the rabbit sciatic nerve gastrocnemius muscle preparation and the blockade was potentiated by neostigmine and not affected by calcium or choline. The compound also blocked the chick biventer cervicis muscle preparation. The blockade was potentiated by neostigmine and offset by doubling the potassium in the external medium. BTM decreased the sensitivity to iontophoretically applied acetylcholine and miniature end-plate potential amplitude. It decreased the resting membrane potentials of both innervated and denervated muscles and blocked the action potentials of both innervated and denervated muscles and blocked the action potential only in high concentrations. BTM is thought to have a dual mechanism of action, a depolarizing type of blockade at lower doses and a blocking action induced by potassium effiux from the cell at higher dose levels.