title: Intracellular magnesium does not antagonize calcium-dependent acetylcholine secretion.
abstract: 1. The effects of intracellular application of Ca and Mg ions on evoked acetylcholine secretion at frog motor nerve terminals were studied. Ca and Mg were applied to the nerve-ending cytoplasm using liposomes as a vehicle. 2. Under conditions in which intracellular application of Ca produced many-fold increased in evoked acetylcholine release. 3. When Mg was applied to the nerve-ending cytoplasm concurrently with Ca, acetylcholine release was further increased above the level produced by introducing Ca alone. 4. The results suggest that intracellular Mg does not antagonize depolarization-secretion coupling and that antagonism of transmitter release by extracellular Mg occurs only at the external surface of the nerve ending.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D003593:Cytoplasm / Q000187:drug effects; D066298:In Vitro Techniques; D008081:Liposomes / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000378:metabolism* / Q000502:physiology; D009469:Neuromuscular Junction / Q000378:metabolism*; D011894:Rana pipiens; D012636:Secretory Rate / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D008081:Liposomes; D008274:Magnesium; D000109:Acetylcholine; D002118:Calcium