Effects of ethidium bromide on the nicotinic acetylcholine receptor

Ethidium bromide was tested for electrophysiological effects at the postsynaptic membrane of the frog muscle endplate. At low concentrations ethidium bromide blocked the open ion channel of the nicotinic acetylcholine receptor and reduced its open time. The rates for channel blocking and unblocking were calculated giving a dissociation constant of 139 nM at -80 mV membrane potential.