title: Three potassium currents in mouse motor nerve terminals.
abstract: A study of the K conductance of the presynaptic membrane has been performed in the triangularis sterni muscle of the mouse. External currents generated in the presynaptic terminals upon invasion by action potentials have been recorded using microelectrodes inserted into the perineurium of preterminal nerve bundles. The voltage-dependent K current could be pharmacologically dissected into fast (IKf) and slow (IKs) components. While both are sensitive to 3,4-diaminopyridine (3,4-DAP), only IKf is sensitive to tetraethylammonium (TEA). Uranyl (100-200 microM) and guanidine (5-10 mM) produced a near complete block of IKf and IKs, which can explain their facilitatory effect upon transmitter release. The third K current of presynaptic terminals is Ca2+-dependent, but was activated also by Sr2+. This current could be suppressed by nanomolar doses of charybdotoxin; it is also sensitive to TEA but not to 3,4-DAP, uranyl or guanidine.
authors.affiliation: Unité de Physiologie Neuromusculaire, Laboratoire de Neurobiologie Cellulaire et Moléculaire, C.N.R.S., Gif sur Yvette, France.
authors.forename: N
authors.initials: N
authors.lastname: Tabti
authors.forename: C
authors.initials: C
authors.lastname: Bourret
authors.forename: A
authors.initials: A
authors.lastname: Mallart
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives*; D000077770:Amifampridine; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D006146:Guanidines / Q000494:pharmacology; D051379:Mice; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009942:Organometallic Compounds / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D006146:Guanidines; D009942:Organometallic Compounds; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; C005460:uranyl acetate; D015761:4-Aminopyridine; D000077770:Amifampridine