alpha-Bungarotoxin and P15 toxin binding site in mammalian sympathetic ganglia.

alpha-Bungarotoxin (alpha-Bgtx) demonstrates a specific and saturable binding to rat superior cervical ganglion, yet it does not block ganglionic response mediated by nicotinic receptors in the guinea pig vas deferens-hypogastric nerve preparation. P15 toxin, a probe for ganglionic nicotinic receptor, prevents the binding of alpha-Bgtx to rat ganglia, and alpha-Bgtx prevents the ganglioplegic action of hexamethonium. Hexamethonium does not block the binding of alpha-Bgtx and P15 to rat ganglia. It is concluded that alpha-Bgtx and P15 bind to ganglionic nicotinic receptor at a common site which is different from that of cholinergic agonists and antagonists.