title: The electrostatic basis of Mg++ inhibition of transmitter release.
abstract: The inhibition by Mg(++) of stimulus-evoked transmitter release is attributed to a decrease in surface potential, Psi(0), on the outer surface of the presynaptic terminal and hence a lower surface calcium concentration, [Ca(++)](0). Data on the frog neuromuscular junction are quantitatively fit by assuming that there is a negative charge density, sigma, on the outer surface of the presynaptic terminal of 6.5 x 10(13) charges per cm(2) and that simple diffuse double layer theory is applicable. No specific binding of Mg(++) or Ca(++) is required. Without any additional assumptions, the inhibitory effect of univalent cations is also quantitatively predicted.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001001:Anura; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003864:Depression, Chemical; D008274:Magnesium / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D008959:Models, Neurological; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D008274:Magnesium; D000109:Acetylcholine; D002118:Calcium