title: Effects of aconitine and batrachotoxin on Na currents and gating currents in the frog node of Ranvier.
abstract: The effects of aconitine and batrachotoxin (BTX) on Na currents and gating currents were studied on voltage clamped frog nodes of Ranvier. The relation between steady-state values of charge movement and test pulse potential (Q-E) was compared with the fraction of open channels at a given potential (F-E). In aconitine-treated nodes the half potential, Emid, of the F-E curve was -87 mV and the slope factor, k, was 6.6 mV. Compared to normal nodes aconitine shifted the F-E curve by -53 mV along the voltage axis without significantly altering the slope. The parameters of the Qon-E curve of aconitine-treated nodes were Emid = -63 mV and k = 18.8 mV compared with Emid = -30 mV and k = 17 mV in a normal node. For the Qoff-E curve Emid was -76 mV, fairly close to Emid of the F-E curve, but the slope remained much smaller than that of the F-E curve. Thus, in aconitine-treated nodes, the normalized Qon-E and Qoff-E curves stay below the F-E curve over almost the whole potential range, a situation different from that in untreated or chloramine-T-treated nodes (Drews 1987). Similar results were obtained with BTX. The F-E curve of BTX-treated fibres had a half potential Emid = -85.1 mV and a slope factor k = 4.7 mV. In contrast to aconitine-treated nodes, the F-E curve showed a secondary rise at E greater than -50 mV.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: I. Physiologisches Institut, Universität des Saarlandes, Homburg, Federal Republic of Germany.
authors.forename: G
authors.initials: G
authors.lastname: Drews
mesh_terms: D000157:Aconitine / Q000494:pharmacology*; D031841:Aconitum / Q000031:analogs & derivatives*; D000818:Animals; D001496:Batrachotoxins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008959:Models, Neurological; D011893:Rana esculenta; D011901:Ranvier's Nodes / Q000187:drug effects* / Q000502:physiology; D012964:Sodium / Q000502:physiology*
chemical_list: D001496:Batrachotoxins; D012964:Sodium; D000157:Aconitine