The Journal of Membrane Biology

, Volume 29, Issue 1, pp 47–65 | Cite as

Potentiation of postjunctional cholinergic sensitivity of rat diaphragm muscle by high-energy-phosphate adenine nucleotides

  • Douglas A. Ewald
Article

Summary

The cholinergic sensitivity of rat diaphragm muscle, measured as the magnitude of depolarization responses to repetitive, iontophoretic pulses of acetylcholine (ACh) onto neuromuscular endplates, is increased by addition of ATP to the perfusion medium. Depolarization responses begin to increase within the first min after addition of 10mm ATP and plateau at 60% above control levels (mean value) after 4 to 6 min. Neither the magnitude nor the time course of the potentiations corresponds to changes in resting potential or membrane resistance. Other nucleotides are equally or less effective at the same concentration: ATP-ADP>UTP>AMP=GTP (=no added nucleotide control) The duration of the individual ACh responses does not increase during continuous exposure to the active nucleotides for up to 15 min except when the muscle is pretreated with eserine.

Mild enzymatic predigestion of the muscle with collagenase and then protease, increasing the availability of the postjunctional membrane to bath-applied drugs, decreases the variability and increases the magnitude of the potentiation to a given dose of ATP. The dose-response curve for ATP is then more than half-maximal at 1mm and the ranking of the other nucleotides relative to ATP is the same as without predigestion.

There is an optimum Ca++ concentration for the potentiation between zero and 2mm: potentiation is enhanced in Ca++-free medium, partially blocked in twice-normal Ca++ medium, and totally blocked in Ca++-free medium 10 min after a 5 min exposure to 2.5mm EGTA. The similar Ca++ dependence of ACh receptor activation in the absence of added nucleotide suggests that ATP directly facilitates receptor activation by ACh. This facilitory action could be one of the physiological roles for the ATP released from stimulated phrenic nerve.

Keywords

Free Medium Phrenic Nerve Adenine Nucleotide Membrane Resistance Perfusion Medium 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Abood, L.G., Koketsu, K., Miyamoto, S. 1962. Outflux of various phosphates during membrane depolarization of excitable tissues.Am. J. Physiol. 202:469Google Scholar
  2. Betz, W., Sakmann, B. 1971. “Disjunction” of frog neuromuscular synapses by treatment with proteolytic enzymes.Nature New Biol. 232:94PubMedGoogle Scholar
  3. Boyd, I.A., Forrester, T. 1968. The release of adenosine triphosphate from frog skeletal musclein vitro.J. Physiol. (London) 199:115Google Scholar
  4. Buchthal, F., Deutsch, A., Knappeis, G.G. 1944. Adenosine-triphosphate initiating contraction and changing birefringence in isolated cross-striated muscle fibers.Nature (London) 153:774Google Scholar
  5. Buchthal, F., Folkow, B. 1948. Interaction between acetylcholine and adenosine triphosphate in normal, curarized, and denervated muscle.Acta Physiol. Scand. 15:150Google Scholar
  6. Dawson, R.M.C., Hauser, H. 1970. Binding of calcium to phospholipids.In: Calcium and Cellular Function. A.W. Cuthbert, editor. pp. 17–41. St. Martin, New YorkGoogle Scholar
  7. Douglas, W.W., Poisner, A.M. 1966. On the relation between ATP splitting and secretion in the adrenal chromaffin cell: Extrusion of ATP (unhydrolyzed) during release of catecholamines.J. Physiol. (London) 183:249Google Scholar
  8. Dowdall, J.J., Boyne, A.F., Whittaker, V.P. 1974. Adenosine triphosphate: A constituent of cholinergic synaptic vesicles.Biochem. J. 140:1PubMedGoogle Scholar
  9. Eccles, J.C., Katz, B., Kuffler, S.W. 1942. Effect of eserine on neuromuscular transmission.J. Neurophysiol. 5:211Google Scholar
  10. Kometiani, Z.P., Kalandarishvili, A.A. 1969. Interrelationship of acetylcholine esterase and transport ATP-ase in the microsomes of the rat brain.Biofizika 14:213PubMedGoogle Scholar
  11. Lambert, D.H., Parsons, R.L. 1970. Influence of polyvalent cations on the activation of muscle end plate receptors.J. Gen. Physiol. 56:309PubMedGoogle Scholar
  12. Magazanik, L.G., Vyskočil, F. 1973. Desensitization at the motor endplate.In: Drug Receptors. H.P. Rang, editor. pp. 105–119. University Park Press, BaltimoreGoogle Scholar
  13. Maheshwari, U.R., Shirachi, D.Y., Trevor, A.J. 1971. Adenosine triphosphate inhibition of ion activated microsomal acetylcholinesterase of ox caudate nucleus.Brain Res. 35:437PubMedGoogle Scholar
  14. Meunier, F.-M., Israël, M., Lesbats, B. 1975. Release of ATP from simulated nerve electroplaque junctions.Nature (London) 257:407Google Scholar
  15. Oliver, A.P. 1971. A simple rapid method for preparing parallel micropipette electrodes.Electroencephelog.Clin. Neurophysiol. 31:284Google Scholar
  16. Silinsky, E.M., Hubbard, J.I. 1973. Release of ATP from rat motor nerve terminals.Nature (London) 243:404Google Scholar
  17. Thesleff, S. 1955. The mode of neuromuscular blockade caused by acetylcholine, nicotine, decamethonium, and succinylcholine.Acta Physiol. Scand. 34:218PubMedGoogle Scholar
  18. Trams, E.G. 1974. Evidence for ATP action on the cell surface.Nature (London) 252:480Google Scholar
  19. Zimmerman, H., Whittaker, V.P. 1974. Effect of electrical stimulation on the yield and composition of synaptic vesicles from the cholinergic synaptic vesicles of the electric organ ofTorpedo: A combined biochemical, electrophysiological, and morphological study.J. Neurochem. 22:435PubMedGoogle Scholar

Copyright information

© Springer-Verlag New York Inc. 1976

Authors and Affiliations

  • Douglas A. Ewald
    • 1
  1. 1.Department of ZoologyUniversity of CaliforniaBerkeley

Personalised recommendations