title: Voltage-dependent changes in the permeability of nerve membranes to calcium and other divalent cations.
abstract: Transmitter release from depolarized nerve terminals seems to be preceded by a rise in the intracellular concentration of ionized calcium. In squid giant axons, depolarization promotes calcium entry by two routes: one that is blocked by tetrodotoxin and one that is insensitive to tetrodotoxin. The TTX-sensitive route seems to be the sodium channel of the action potential; but the TTX-insensitive route seems to be quite distinct from the sodium and potassium channels of the action potential. It is blocked by Mg-2+, Mn-2+ and Co-2+ ions and by the organic calcium antagonist D-600 and has many features in common with the mechanism that couples excitation to secretion.
mesh_terms: D000200:Action Potentials; D000331:Aequorin / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002413:Cations, Divalent; D003035:Cobalt / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008345:Manganese / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism; D009441:Neurilemma / Q000378:metabolism*; D009474:Neurons / Q000502:physiology / Q000648:ultrastructure; D012964:Sodium / Q000378:metabolism; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002132:Calcium Radioisotopes; D002413:Cations, Divalent; D013757:Tetraethylammonium Compounds; D003035:Cobalt; D008345:Manganese; D013779:Tetrodotoxin; D000331:Aequorin; D012964:Sodium; D014700:Verapamil; D008274:Magnesium; D002118:Calcium