Luminescence control of Amphipholis squamata (Ophiuroidea): Nature of cholinergic receptors

Acetylcholine application on isolated arms of Amphipholis squamata induced a luminescent response. We investigated the nature of the cholinergic receptors involved in the luminescence control of Amphipholis. Nicotinic antagonists, tubocurarine and butyrylcholine chloride, had no inhibitory effect. Muscarinic antagonists, atropine and benzotropine mesylate, inhibited Amphipholis lurriinescence. The effects of specific M₁ and M₂ muscarinic agonists and antagonists suggest the presence of muscarinic receptors with predominance of M₂ subtype receptors.