Kappa-bungarotoxin: an intracellular study demonstrating blockade of neuronal nicotinic receptors by a snake neurotoxin.

Pressure injection of carbachol elicited dose-dependent depolarizations of the principal ganglionic neurons in embryonic chick ciliary ganglia. These depolarizations were associated with a marked decrease in input resistance. Carbachol-induced depolarizations were completely and reversibly antagonized by the snake neurotoxin Kappa-bungarotoxin but not by alpha-bungarotoxin. Kappa-bungarotoxin, therefore, appears to be a specific probe for the postsynaptic neuronal nicotinic receptor in the avian ciliary ganglion.