The neuromuscular blocking action of a series of bicyclic bis-oniu esters.

1. Thirteen bicyclic dicholine esters have been tested on mammalian and avian skeletal muscle preparations.2. One of the compounds exhibited depolarizing activity in all the preparations.3. Three of the compounds exhibited depolarizing or dual-blocking activity in avian and denervated mammalian preparations, but exhibited non-depolarizing blocking activity in innervated mammalian preparations.4. The remaining compounds exhibited non-depolarizing blocking activity with evidence of an additional facilitatory action.5. The activity exhibited was dependent upon the onium substituents and the structure of the bicyclic ring.6. All the compounds exhibited a choline-reversible block in the rapidly stimulated rat diaphragm preparation and six of them exhibited a secondary choline-reversible block of the rapidly stimulated cat tibialis anterior muscle.