Abstract
Membrane currents were recorded from nonmyelinated frog endings by external electrodes. Changes in shape of the signals recorded at varying distances from the myelin end could be explained by assuming a non uniform distribution of Na and K channels along the presynaptic terminal. Specific channel blocking agents revealed that Na channels are present in highest density in the first half of each terminal branch and at almost undetectable levels near the extreme end, while K channels show a more widespread distribution with higher density at medial parts. Suppression of K conductance revealed Ca current which was seen as outward current near the myelin end.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Atwood HL (1976) Organization and synaptic physiology of crustacean neuromuscular systems. Progr Neurobiol 7:291–391
Benoit PR, Mabrini J (1970) Modification of transmitter release by ions which prolong the presynaptic action potential. J Physiol (Lond) 210:681–695
Bostock H, Searts TA, Sherratt RM (1981) The effects of 4-aminopyridine and tetraethylammonium ions normal and demyelinated mammalian nerve fibres. J Physiol (Lond) 313:301–315
Braun M, Schmidt RF (1966) Potential changes recorded from the motor nerve terminal during its activation. Pflügers Arch 287:56–80
Brigant JL, Mallart A (1982) Presynaptic currents in mouse motor endings. J Physiol (Lond) 333:619–636
Brismar T (1980) Potential clamp analysis of membrane currents in rat myelinated nerve fibres. J Physiol (Lond) 298:171–184
Burley ES, Jacobs RS (1981) Effects of 4-aminopyridine on nerve terminal action potentials. J Pharmacol Exper Ther 219:268–273
Chiu SY, Ritchie JM, Rogart RB, Stagg D (1979) A quantitative description of membrane currents in rabbit myelinated nerve. J Physiol (Lond) 292:149–166
Dudel J (1982) Transmitter release by graded local depolarization of presynaptic nerve terminals at the crayfish neuromuscular junction. Neurosci Lett 32:181–186
Eccles JC (1964) The physiology of synapses. Academic Press, New York, p 124
Gundersen CB, Katz B, Miledi R (1982) The antagonism of botulinium toxin and calcium in motor nerve terminals. Proc R Soc Lond B 216:369–376
Hodgkin AL, Huxley AF (1952) A quantitative description of membrane currents and its application to conduction and excitation in nerve. J Physiol (Lond) 117:500–544
Katz B, Miledi R (1965) Propagation of electric activity in motor nerve terminals. Proc R Soc (Lond) B 161:453–482
Katz B, Miledi R (1968) The effect of local blockage of motor nerve terminals. J Physiol (Lond) 199:729–741
Kirsch GE, Narahashi T (1978) 3,4-diaminopyridine. A potent new potassium channel blocker. Biophys J 22:507–512
Landh H, Thesleff S (1977) The mode of action of 4-aminopyridine and guanidine on transmitter release from motor nerve terminals. Eur J Pharmacol 42:411–412
Mallart A, Brigant JL (1982) Electrical activity at motor nerve terminals of the mouse. J Physiol (Paris) 78:407–411
Molgo J (1982) Effects of aminopyridines in neuromuscular transmission. In: Bowman WC, Lechat P, Thesleff S (eds) Aminopyridines and similary acting drugs. Pergamon Press, Oxford, p 95
Smith KJ, Schauf CL (1981) Size dependent variation of nodal properties in myelinated nerve. Nature Lond 293:297–298
Stämpfli R, Hille B (1976) Electrophysiology of the peripheral nerve. In: Llinás R, Precht W (eds) Frog neurobiology. Springer, Berlin Heidelberg New York, p 3
Thieffry M, Bruner J (1978) Direct evidence for a presynaptic action of glutamate at a crayfish neuromuscular junction. Brain Res 156:402–406
Zucker R (1974) Crayfish neuromuscular facilitation activated by constrant presynaptic action potentials and depolarizing pulses. J Physiol (Lond) 241:69–89
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Mallart, A. Presynaptic currents in frog motor endings. Pflugers Arch. 400, 8–13 (1984). https://doi.org/10.1007/BF00670529
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00670529