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. 1985 Oct;367:163–181. doi: 10.1113/jphysiol.1985.sp015819

Calcium entry and transmitter release at voltage-clamped nerve terminals of squid.

G J Augustine, M P Charlton, S J Smith
PMCID: PMC1193058  PMID: 2865362

Abstract

Presynaptic and post-synaptic cells of the squid giant synapse were voltage-clamped simultaneously to study the relationship between presynaptic Ca current and transmitter-induced post-synaptic current (p.s.c.). Local Ca application was used to restrict Ca current and transmitter release to a limited region of the presynaptic terminal and thus minimize errors due to spatial heterogeneity of presynaptic membrane potential. Presynaptic terminals were depolarized by brief (3-6 ms) voltage-clamp pulses of varying amplitude to collect graded series of presynaptic Ca current and p.s.c. records. During presynaptic depolarization at 14 degrees C, Ca current activation preceded initial onset of p.s.c. (on-p.s.c.) by an interval of approximately 1 ms. The main component of on-p.s.c. followed Ca current activation by about 2 ms. The delay between a brief Ca tail current and peak response of the p.s.c. produced after pulse termination (off-p.s.c.) was also approximately 2 ms. Curves relating both Ca current and p.s.c. magnitudes to presynaptic potential were bell shaped with peaks near -10 mV, but the p.s.c. curve showed stronger voltage dependence on both sides of the peak. With very small and very large presynaptic command pulses, Ca current could be observed without measureable p.s.c. Synaptic transfer curves, plotting p.s.c. as a function of presynaptic Ca current, resembled third-power functions. On the average, p.s.c.s fit a curve representing the 2.9 power of Ca current (range 2.4-3.5 in eighteen experiments). Transfer curves consisted of two limbs: one from presynaptic pulses below -10 mV and the other from more positive pulses. These two limbs were similar and generally resembled power functions of identical exponent. It is thus likely that the third-power function accurately reflects synaptic current transfer, rather than interference from some other voltage-dependent process. Power functions fitting small-pulse and large-pulse limbs of some transfer curves had different scale coefficients, even though exponent values were the same. Consideration of synaptic transmission kinetics suggests that the voltage dependence of Ca channel opening rates can probably explain the difference in transfer curve limbs. Our experiments provide no evidence for an intrinsic voltage dependence of the transmitter release process.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Alnaes E., Rahamimoff R. On the role of mitochondria in transmitter release from motor nerve terminals. J Physiol. 1975 Jun;248(2):285–306. doi: 10.1113/jphysiol.1975.sp010974. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Augustine G. J., Charlton M. P., Smith S. J. Calcium entry into voltage-clamped presynaptic terminals of squid. J Physiol. 1985 Oct;367:143–162. doi: 10.1113/jphysiol.1985.sp015818. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Augustine G. J., Eckert R. Divalent cations differentially support transmitter release at the squid giant synapse. J Physiol. 1984 Jan;346:257–271. doi: 10.1113/jphysiol.1984.sp015020. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bixby J. L., Spitzer N. C. Enkephalin reduces quantal content at the frog neuromuscular junction. Nature. 1983 Feb 3;301(5899):431–432. doi: 10.1038/301431a0. [DOI] [PubMed] [Google Scholar]
  5. Charlton M. P., Smith S. J., Zucker R. S. Role of presynaptic calcium ions and channels in synaptic facilitation and depression at the squid giant synapse. J Physiol. 1982 Feb;323:173–193. doi: 10.1113/jphysiol.1982.sp014067. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Dodge F. A., Jr, Rahamimoff R. Co-operative action a calcium ions in transmitter release at the neuromuscular junction. J Physiol. 1967 Nov;193(2):419–432. doi: 10.1113/jphysiol.1967.sp008367. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Dunlap K., Fischbach G. D. Neurotransmitters decrease the calcium ocmponent of sensory neurone action potentials. Nature. 1978 Dec 21;276(5690):837–839. doi: 10.1038/276837a0. [DOI] [PubMed] [Google Scholar]
  8. Gorman A. L., Levy S., Nasi E., Tillotson D. Intracellular calcium measured with calcium-sensitive micro-electrodes and Arsenazo III in voltage-clamped Aplysia neurones. J Physiol. 1984 Aug;353:127–142. doi: 10.1113/jphysiol.1984.sp015327. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. HAGIWARA S., TASAKI I. A study on the mechanism of impulse transmission across the giant synapse of the squid. J Physiol. 1958 Aug 29;143(1):114–137. doi: 10.1113/jphysiol.1958.sp006048. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Hagiwara S., Byerly L. Calcium channel. Annu Rev Neurosci. 1981;4:69–125. doi: 10.1146/annurev.ne.04.030181.000441. [DOI] [PubMed] [Google Scholar]
  11. Hartzell H. C., Kuffler S. W., Yoshikami D. Post-synaptic potentiation: interaction between quanta of acetylcholine at the skeletal neuromuscular synapse. J Physiol. 1975 Oct;251(2):427–463. doi: 10.1113/jphysiol.1975.sp011102. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Katz B., Miledi R. Further study of the role of calcium in synaptic transmission. J Physiol. 1970 May;207(3):789–801. doi: 10.1113/jphysiol.1970.sp009095. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Katz B., Miledi R. The role of calcium in neuromuscular facilitation. J Physiol. 1968 Mar;195(2):481–492. doi: 10.1113/jphysiol.1968.sp008469. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Klein M., Kandel E. R. Presynaptic modulation of voltage-dependent Ca2+ current: mechanism for behavioral sensitization in Aplysia californica. Proc Natl Acad Sci U S A. 1978 Jul;75(7):3512–3516. doi: 10.1073/pnas.75.7.3512. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Knight D. E., Baker P. F. Calcium-dependence of catecholamine release from bovine adrenal medullary cells after exposure to intense electric fields. J Membr Biol. 1982;68(2):107–140. doi: 10.1007/BF01872259. [DOI] [PubMed] [Google Scholar]
  16. Kusano K., Landau E. M. Depression and recovery of transmission at the squid giant synapse. J Physiol. 1975 Feb;245(1):13–32. doi: 10.1113/jphysiol.1975.sp010832. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Lester H. A. Transmitter release by presynaptic impulses in the squid stellate ganglion. Nature. 1970 Aug 1;227(5257):493–496. doi: 10.1038/227493a0. [DOI] [PubMed] [Google Scholar]
  18. Llinás R., Steinberg I. Z., Walton K. Presynaptic calcium currents and their relation to synaptic transmission: voltage clamp study in squid giant synapse and theoretical model for the calcium gate. Proc Natl Acad Sci U S A. 1976 Aug;73(8):2918–2922. doi: 10.1073/pnas.73.8.2918. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Llinás R., Steinberg I. Z., Walton K. Presynaptic calcium currents in squid giant synapse. Biophys J. 1981 Mar;33(3):289–321. doi: 10.1016/S0006-3495(81)84898-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Llinás R., Steinberg I. Z., Walton K. Relationship between presynaptic calcium current and postsynaptic potential in squid giant synapse. Biophys J. 1981 Mar;33(3):323–351. doi: 10.1016/S0006-3495(81)84899-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Llinás R., Sugimori M., Simon S. M. Transmission by presynaptic spike-like depolarization in the squid giant synapse. Proc Natl Acad Sci U S A. 1982 Apr;79(7):2415–2419. doi: 10.1073/pnas.79.7.2415. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. MARTIN A. R. A further study of the statistical composition on the end-plate potential. J Physiol. 1955 Oct 28;130(1):114–122. doi: 10.1113/jphysiol.1955.sp005397. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Mann D. W., Joyner R. W. Miniature synaptic potentials at the squid giant synapse. J Neurobiol. 1978 Jul;9(4):329–335. doi: 10.1002/neu.480090410. [DOI] [PubMed] [Google Scholar]
  24. Miledi R. Spontaneous synaptic potentials and quantal release of transmitter in the stellate ganglion of the squid. J Physiol. 1967 Sep;192(2):379–406. doi: 10.1113/jphysiol.1967.sp008306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Nachshen D. A., Drapeau P. A buffering model for calcium-dependent neurotransmitter release. Biophys J. 1982 May;38(2):205–208. doi: 10.1016/S0006-3495(82)84548-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Onodera K., Takeuchi A. Distribution and pharmacological properties of synaptic and extrasynaptic glutamate receptors on crayfish muscle. J Physiol. 1980 Sep;306:233–250. doi: 10.1113/jphysiol.1980.sp013394. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Pumplin D. W., Reese T. S., Llinás R. Are the presynaptic membrane particles the calcium channels? Proc Natl Acad Sci U S A. 1981 Nov;78(11):7210–7213. doi: 10.1073/pnas.78.11.7210. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Rahamimoff R. A dual effect of calcium ions on neuromuscular facilitation. J Physiol. 1968 Mar;195(2):471–480. doi: 10.1113/jphysiol.1968.sp008468. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Rahamimoff R., Meiri H., Erulkar S. D., Barenholz Y. Changes in transmitter release induced by ion-containing liposomes. Proc Natl Acad Sci U S A. 1978 Oct;75(10):5214–5216. doi: 10.1073/pnas.75.10.5214. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Reichardt L. F., Kelly R. B. A molecular description of nerve terminal function. Annu Rev Biochem. 1983;52:871–926. doi: 10.1146/annurev.bi.52.070183.004255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Requena J., DiPolo R., Brinley F. J., Jr, Mullins L. J. The control of ionized calcium in squid axons. J Gen Physiol. 1977 Sep;70(3):329–353. doi: 10.1085/jgp.70.3.329. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Smith S. J., Augustine G. J., Charlton M. P. Transmission at voltage-clamped giant synapse of the squid: evidence for cooperativity of presynaptic calcium action. Proc Natl Acad Sci U S A. 1985 Jan;82(2):622–625. doi: 10.1073/pnas.82.2.622. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Stevens C. F. A comment on Martin's relation. Biophys J. 1976 Aug;16(8):891–895. doi: 10.1016/S0006-3495(76)85739-6. [DOI] [PMC free article] [PubMed] [Google Scholar]

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