title: Reappearance of miniature endplate potentials in frog neuromuscular junctions "silenced" by lanthanum ions.
abstract: Miniature endplate potentials and currents were recorded from frog sartorius muscle fibres. As expected from previous work, La3+ caused a very large increase in miniature endplate potential frequency, followed by a progressive decrease, ending in the virtually complete disappearance of miniature endplate potentials. Soon after its application, La3+ caused an increase in the amplitude of miniature endplate potentials due to a lengthening of the underlying miniature endplate currents. Analysis of membrane current fluctuations produced by acetylcholine showed that La3+ caused an increase in the lifetime of the channels opened by acetylcholine. After miniature endplate potentials had vanished following La3+ treatment, the muscles were placed in organ culture conditions to see if miniature endplate potentials would reappear. After several hours miniature endplate potential activity was resumed in about 25% of the endplates, and disappeared again a few hours later, presumably because of accelerated nerve terminal degeneration. Preliminary electron microscopic observations suggest that the recovery of miniature endplate potential activity was accompanied by re-formation of synaptic vesicles in the motor endings.
authors.affiliation: Department of Biophysics, University College London, U.K.
authors.forename: M I
authors.initials: MI
authors.lastname: Glavinović
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: R
authors.initials: R
authors.lastname: Miledi
mesh_terms: D000818:Animals; D007811:Lanthanum / Q000494:pharmacology*; D009045:Motor Endplate / Q000187:drug effects / Q000502:physiology*; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D011896:Rana temporaria; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D007811:Lanthanum