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The timing of channel opening during miniature endplate currents at the frog and mouse neuromuscular junctions: effects of fasciculin-2, other anti-cholinesterases and vesamicol

Abstract

Fluctuation analysis was used to estimate the mean single-channel conductance and the mean channel duration of opening. Miniature endplate currents (MEPCs) were measured with the voltage-clamp technique. The timing of endplate channel opening during the generation of the MEPC was estimated by a deconvolution method. Often all of the channels opened during the rise of the MEPC, but in about half of the examples some 10% of the channels opened after the peak. We studied the effects of acetylcholinesterase (AChE) inhibition with neostigmine, diisopropyl fluorophosphate (DFP) and fasciculin-2. With AChE largely inhibited, the number of channels opening increased as much as fourfold, largely by channels opening in the “tail” that follows the peak of the MEPC. The results were compared to models of MEPC generation. Models did not account well for the pattern of channel opening, particularly after AChE inhibition. In the presence of fasciculin-2, the addition of 2 μM (−)-vesamicol reduced the number of channels opening and shortened the period over which channels were open. One interpretation is that quantal ACh release is not almost instantaneous, but that some of the ACh is released over a period of a millisecond or more and that some of the release is blocked by (−)-vesamicol.

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References

  1. 1.

    Anderson AJ, Harvey AL, Mbugua PM (1985) Effects of fasciculin-2, an anticholinesterase polypeptide from green mamba venom, on neuromuscular transmission in mouse diaphragm preparations. Neurosci Lett 54:123–128

  2. 2.

    Anderson CR, Stevens CF (1973) Voltage clamp analysis of acetylcholine produced end-plate current fluctuations at frog neuromuscular junction. J Physiol (Lond) 235:655–691

  3. 3.

    Bartol TM Jr, Land BR, Salpeter EE, Salpeter MM (1991) Monte Carlo simulation of miniature endplate current generation in the vertebrate neuromuscular junction. Biophys J 59:1290–1307

  4. 4.

    Chang CC, Hong SJ, Lin H-L, Su MJ (1985) Acetylcholine hydrolysis during neuromuscular transmission in the synaptic cleft of skeletal muscle of mouse and chick. Neuropharmacology 24:533–539

  5. 5.

    Cohen I, Van der Kloot W, Attwell D (1981) The timing of channel opening during miniature and-plate currents. Brain Research 223:185–189

  6. 6.

    Colquhoun D, Large WA, Rang HP (1977) An analysis of the action of a false transmitter at the neuromuscular junction. J Physiol (Lond) 266:361–395

  7. 7.

    Edwards C, Dolezal V, Tucek S, Zemkova H, Vyskocil F (1985) Is an acetylcholine transport system responsible for nonquantal release of acetylcholine at the rodent myoneural junction? Proc Natl Acad Sci USA 82:3514–3518

  8. 8.

    Ellman GL, Courtney KD, Andres V Jr, Featherstone RM (1961) A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 7:88–95

  9. 9.

    Gage PW, McBurney RN (1975) Effects of membrane potential, temperature and neostigmine on the conductance change caused by a quantum of acetylcholine at the toad neuromuscular junction. J Physiol (Lond) 244:385–407

  10. 10.

    Gage PW, Van Helden D (1979) Effects of permanent monovalent cations on end-plate channels. J Physiol (Lond) 288:509–528

  11. 11.

    Giniatullin RA, Khamitov G, Khazipov R, Magazanik LG, Nikolsky EE, Snetkov VA, Vyskocil F (1989) Development of desensitization during repetitive end-plate activity and single end-plate currents in frog muscle. J Physiol (Lond) 412:113–122

  12. 12.

    Henderson EG, Post-Munson DJ, Reynolds LS, Epstein PM (1989) Echothiophate and cogeners decrease the voltage dependence of end-plate current decay in frog skeletal muscle. J Pharmacol Exp Ther 251:810–816

  13. 13.

    Karlsson E, Mbugua PM, Rodriguez-Ithurralde D (1985) Anticholinesterase toxins. Pharmacol Ther 30:259–276

  14. 14.

    Katz B, Miledi R (1973) The binding of acetylcholine to receptors and its removal from the synaptic cleft. J Physiol (Lond) 231:549–574

  15. 15.

    Katz B, Miledi R (1975) The nature of the prolonged endplate depolarization in anti-esterase treated muscle. Proc R Soc Lond [Biol] 192:27–38

  16. 16.

    Land BR, Salpeter EE, Salpeter MM (1980) Acetylcholine receptor site density affects the rising phase of miniature endplate currents. Proc Natl Acad Sci USA 77:3736–3740

  17. 17.

    Lupa MT, Tabti N, Thesleff S, Vyskocil F, Yu SP (1986) The nature and origin of calcium-insensitive miniature end-plate potentials at rodent neuromuscular junctions. J Physiol (Lond) 381:607–618

  18. 18.

    Madsen BW, Edeson RO, Lam HS, Milne RK (1984) Numerical simulation of miniature endplate currents. Neurosci Lett: 67–74

  19. 19.

    Magazanik LG, Snetkov VA, Giniatullin RA, Khazipov RN (1990) Changes in the time course of miniature endplate currents induced by bath-applied acetylcholine. Neuroscience Lett 113:281–285

  20. 20.

    Magleby KL, Stevens CF (1972) A quantitative description of end-plate currents. J Physiol (Lond) 223:173–197

  21. 21.

    Mittag TW, Ehrenpreis S, Hehir RM (1971) Functional acetylcholinesterase of rat diaphragm muscle. Biochem Pharmacol 20:2263–2273

  22. 22.

    Molgó J, Thesleff S (1982) 4-Aminoquinoline-induced ‘giant’ miniature endplate potentials at mammalian neuromuscular junctions. Proc R Soc Lond [Biol] 214:229–247

  23. 23.

    Molgó J, Magazanik LG, Hermel JM, Juzans P, Stinnakre J, Karlsson E (1993) Actions of fasciculin-1 and -2, anticholinesterase peptides isolated from green mamba venom, on endplate currents at the neuromuscular junction. (Abstracts of the Xth European Symposium on Animal, Plant and Microbial Toxins, Paris, France). Toxicon 31:536

  24. 24.

    Neher E, Sakmann B (1976) Noise analysis of drug induced voltage clamp currents in denervated frog muscle fibres. J Physiol (Lond) 258:705–729

  25. 25.

    Nigmatullin NR, Snetkov VA, Nikol'skii EE, Magazanik LG (1988) Modelling of miniature endplate current. Neirofiziologiya 20:390–397

  26. 26.

    Parnas H, Flashner M, Spira ME (1989) Sequential model to describe the nicotinic synaptic current. Biophys J 55:875–884

  27. 27.

    Prior C, Marshall IG, Parsons SM (1992) The pharmacology of vesamicol — an inhibitor of the vesicular acetylcholine transporter. Gen Pharmacol 23:1017–1022

  28. 28.

    Rosenberry TL (1979) Quantitative simulation of endplate currents at neuromuscular junctions based on the reaction of acetylcholine with acetylcholine receptor and acetylcholinesterase. Biophys J 26:263–290

  29. 29.

    Salpeter MM (1987) Vertebrate neuromuscular junctions: general morphology, molecular organization, and functional consequences. In: Salpeter MM (ed) The vertebrate neuromuscular junction. Liss, New York, pp 1–54

  30. 30.

    Schwartz M, Shaw L (1975) Signal processing: discrete spectral analysis, detection, and estimation. McGraw-Hill, New York, p 396

  31. 31.

    Scuka M, Mozrzymas JW (1992) Postsynaptic potentiation and desensitization at the vertebrate end-plate receptors. Progr Neurobiol 38:11–33

  32. 32.

    Sheridan RE, Lester HA (1977) Rates and equilibria at the acetylcholine receptor of electrophorus electroplaques. J Gen Physiol 70:187–219

  33. 33.

    Stavitzky A, Golay J (1964) Smoothing and differentiation of data by simplified least square procedure. Anal Chem 36:1627–1639

  34. 34.

    Thesleff S, Molgó J (1983) A new type of transmitter release at the neuromuscular junction. Neuroscience 9:1–8

  35. 35.

    Van der Kloot W (1988) Estimating the timing of quantal releases during end-plate currents at the frog neuromuscular junction. J Physiol (Lond) 402:595–603

  36. 36.

    Van der Kloot W (1988) The kinetics of quantal releases during end-plate currents at the frog neuromuscular junction. J Physiol (Lond) 402:605–626

  37. 37.

    Van der Kloot W (1991) The regulation of quantal size. Progr Neurobiol 36:93–130

  38. 38.

    Wathey JC, Nass MM, Lester HA (1979) Numerical reconstruction of the quantal event at nicotinic synapses. Biophys J 27:145–164

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Correspondence to William Van der Kloot.

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Van der Kloot, W., Balezina, O.P., Molgó, J. et al. The timing of channel opening during miniature endplate currents at the frog and mouse neuromuscular junctions: effects of fasciculin-2, other anti-cholinesterases and vesamicol. Pflügers Arch 428, 114–126 (1994). https://doi.org/10.1007/BF00374848

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Key words

  • Acetylcholine
  • Neuromuscular junction
  • Quantum
  • Synapse
  • Endplate current
  • Anticholinesterase