Skip to main content
NCBI home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1983 Feb;335:89–100. doi: 10.1113/jphysiol.1983.sp014521

The calcium component of the action potential in spinal motoneurones of the rat.

Y Harada, T Takahashi
PMCID: PMC1197340  PMID: 6875900

Abstract

Intracellular recordings were made from motoneurones of the neonatal rat (1-14 days old) spinal cord isolated and perfused in vitro. An increase in extracellular Ca2+ concentration from 2 to 20 mM produced an increase in the amplitude of the after-depolarization (a.d.p.), while replacement of Ca2+ by Mn2+ virtually abolished the a.d.p. These changes in the a.d.p. occurred in parallel with those in the after-hyperpolarization (a.h.p.). The amplitudes of the a.d.p. and the a.h.p. were dependent upon the membrane potential: hyperpolarization increased the a.d.p. and decreased the a.h.p.; the opposite effects were produced by depolarization. The presence of Ca2+ spikes was demonstrated either by suppression of the voltage-dependent K+ conductance with tetraethylammonium (TEA) or after blocking the Na+ spike. The Ca2+ spike was all-or-none in nature and blocked by Mn2+ or Co2+. The a.h.p. amplitude was dependent upon the extracellular K+ concentration but also correlated with the amplitude of the Ca2+-dependent response. It is concluded that the a.d.p. is a Ca2+-dependent potential whose amplitude is under normal conditions markedly reduced by the voltage-dependent K+ conductance; the a.h.p. seems to be produced by an increase in the Ca2+-dependent K+ conductance.

Full text

PDF
89

Selected References

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

  1. Alvarez-Leefmans F. J., Miledi R. Voltage sensitive calcium entry in frog motoneurones. J Physiol. 1980 Nov;308:241–257. doi: 10.1113/jphysiol.1980.sp013470. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. BROCK L. G., COOMBS J. S., ECCLES J. C. The recording of potentials from motoneurones with an intracellular electrode. J Physiol. 1952 Aug;117(4):431–460. doi: 10.1113/jphysiol.1952.sp004759. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Baldissera F., Gustafsson B. Afterhyperpolarization conductance time course in lumbar motoneurones of the cat. Acta Physiol Scand. 1974 Aug;91(4):512–527. doi: 10.1111/j.1748-1716.1974.tb05707.x. [DOI] [PubMed] [Google Scholar]
  4. Barrett E. F., Barret J. N. Separation of two voltage-sensitive potassium currents, and demonstration of a tetrodotoxin-resistant calcium current in frog motoneurones. J Physiol. 1976 Mar;255(3):737–774. doi: 10.1113/jphysiol.1976.sp011306. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Blankenship J. E. Action of tetrodotoxin on spinal motoneurons of the cat. J Neurophysiol. 1968 Mar;31(2):186–194. doi: 10.1152/jn.1968.31.2.186. [DOI] [PubMed] [Google Scholar]
  6. COOMBS J. S., ECCLES J. C., FATT P. The electrical properties of the motoneurone membrane. J Physiol. 1955 Nov 28;130(2):291–325. doi: 10.1113/jphysiol.1955.sp005411. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Fulton B. P., Miledi R., Takahashi T. Electrical synapses between motoneurons in the spinal cord of the newborn rat. Proc R Soc Lond B Biol Sci. 1980 Jun 23;208(1170):115–120. doi: 10.1098/rspb.1980.0045. [DOI] [PubMed] [Google Scholar]
  8. GRANIT R., KERNELL D., SMITH R. S. DELAYED DEPOLARIZATION AND THE REPETITIVE RESPONSE TO INTRACELLULAR STIMULATION OF MAMMALIAN MOTONEURONES. J Physiol. 1963 Oct;168:890–910. doi: 10.1113/jphysiol.1963.sp007229. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Gustafsson B. Afterhyperpolarization and the control of repetitive firing in spinal neurones of the cat. Acta Physiol Scand Suppl. 1974;416:1–47. [PubMed] [Google Scholar]
  10. KERNELL D. THE DELAYED DEPOLARIZATION IN CAT AND RAT MOTONEURONES. Prog Brain Res. 1964;12:42–55. doi: 10.1016/s0079-6123(08)60616-0. [DOI] [PubMed] [Google Scholar]
  11. Katz B., Miledi R. Tetrodotoxin-resistant electric activity in presynaptic terminals. J Physiol. 1969 Aug;203(2):459–487. doi: 10.1113/jphysiol.1969.sp008875. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Krnjević K., Lamour Y., MacDonald J. F., Nistri A. Effects of some divalent cations on motoneurones in cats. Can J Physiol Pharmacol. 1979 Sep;57(9):944–956. doi: 10.1139/y79-144. [DOI] [PubMed] [Google Scholar]
  13. Krnjević K., Lisiewicz A. Injections of calcium ions into spinal motoneurones. J Physiol. 1972 Sep;225(2):363–390. doi: 10.1113/jphysiol.1972.sp009945. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Krnjević K., Puil E., Werman R. EGTA and motoneuronal after-potentials. J Physiol. 1978 Feb;275:199–223. doi: 10.1113/jphysiol.1978.sp012186. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Lederer W. J., Spindler A. J., Eisner D. A. Thick slurry bevelling: a new technique for bevelling extremely fine microelectrodes and micropipettes. Pflugers Arch. 1979 Sep;381(3):287–288. doi: 10.1007/BF00583261. [DOI] [PubMed] [Google Scholar]
  16. Meech R. W. Intracellular calcium injection causes increased potassium conductance in Aplysia nerve cells. Comp Biochem Physiol A Comp Physiol. 1972 Jun 1;42(2):493–499. doi: 10.1016/0300-9629(72)90128-4. [DOI] [PubMed] [Google Scholar]
  17. Nelson P. G., Burke R. E. Delayed depolarization in cat spinal motoneurons. Exp Neurol. 1967 Jan;17(1):16–26. doi: 10.1016/0014-4886(67)90118-5. [DOI] [PubMed] [Google Scholar]
  18. Otsuka M., Konishi S. Electrophysiology of mammalian spinal cord in vitro. Nature. 1974 Dec 20;252(5485):733–734. doi: 10.1038/252733a0. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

RESOURCES