title: The non-competitive acetylcholinesterase inhibitor APS12-2 is a potent antagonist of skeletal muscle nicotinic acetylcholine receptors.
abstract: APS12-2, a non-competitive acetylcholinesterase inhibitor, is one of the synthetic analogs of polymeric alkylpyridinium salts (poly-APS) isolated from the marine sponge Reniera sarai. In the present work the effects of APS12-2 were studied on isolated mouse phrenic nerve-hemidiaphragm muscle preparations, using twitch tension measurements and electrophysiological recordings. APS12-2 in a concentration-dependent manner blocked nerve-evoked isometric muscle contraction (IC(50)=0.74 μM), without affecting directly-elicited twitch tension up to 2.72 μM. The compound (0.007-3.40 μM) decreased the amplitude of miniature endplate potentials until a complete block by concentrations higher than 0.68 μM, without affecting their frequency. Full size endplate potentials, recorded after blocking voltage-gated muscle sodium channels, were inhibited by APS12-2 in a concentration-dependent manner (IC(50)=0.36 μM) without significant change in the resting membrane potential of the muscle fibers up to 3.40 μM. The compound also blocked acetylcholine-evoked inward currents in Xenopus oocytes in which Torpedo (α1(2)β1γδ) muscle-type nicotinic acetylcholine receptors (nAChRs) have been incorporated (IC(50)=0.0005 μM), indicating a higher affinity of the compound for Torpedo (α1(2)β1γδ) than for the mouse (α1(2)β1γε) nAChR. Our data show for the first time that APS12-2 blocks neuromuscular transmission by a non-depolarizing mechanism through an action on postsynaptic nAChRs of the skeletal neuromuscular junction.
authors.affiliation: Institute of Physiology, Pharmacology and Toxicology, Veterinary Faculty, University of Ljubljana, Gerbičeva 60, SI-1000 Ljubljana, Slovenia.
authors.forename: Marjana
authors.initials: M
authors.lastname: Grandič
authors.forename: Romulo
authors.initials: R
authors.lastname: Aráoz
authors.forename: Jordi
authors.initials: J
authors.lastname: Molgó
authors.forename: Tom
authors.initials: T
authors.lastname: Turk
authors.forename: Kristina
authors.initials: K
authors.lastname: Sepčić
authors.forename: Evelyne
authors.initials: E
authors.lastname: Benoit
authors.forename: Robert
authors.initials: R
authors.lastname: Frangež
mesh_terms: D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D055369:Miniature Postsynaptic Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects; D018733:Nicotinic Antagonists; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D011726:Pyridinium Compounds / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012044:Regression Analysis; D014981:Xenopus
chemical_list: C561372:1,3-dodecylpyridinium bromide; D002800:Cholinesterase Inhibitors; D018733:Nicotinic Antagonists; D011726:Pyridinium Compounds; D011978:Receptors, Nicotinic