Histamine as an endogenous antagonist of nicotinic ACh-receptor

The mechanism of an inhibitory effect of histamine on the sensitivity of frog skeletal muscle endplate was analyzed by studying the dose-response relation between the quantity of ACh applied iontophoretically and the ACh-induced postsynaptic current (ACh current), and also the interaction between histamine and erabutoxin-b (ETX-b). The results obtained show that histamine, like curare, decreased the sensitivity of ACh-receptor in a competitive manner.