Skip to main content
PMC home page
The Journal of General Physiology logoLink to The Journal of General Physiology
. 1970 Nov 1;56(5):543–558. doi: 10.1085/jgp.56.5.543

Mechanism of Excitation of Aplysia Neurons by Carbon Dioxide

A M Brown 1, P R Berman 1
PMCID: PMC2225973  PMID: 4319973

Abstract

The abdominal ganglion of Aplysia californica was perfused with artificial seawater equilibrated at different P COCO2's and pH's for 5 min or less. 5% CO2 dropped perfusate pH from 8.0 to 6.5 and produced depolarization and increased discharge rate in visceromotor neurons. Half the giant cells studied had a similar response, whereas the other half were hyperpolarized. Pacemaker neurons showed little, if any, response to such changes in pH or CO2. Membrane conductance of responsive cells was always increased. The effect of CO2 occurred even when synaptic transmission was blocked by low calcium and high magnesium, and therefore must have been a direct result of CO2 or the concomitant fall in pH. When extracellular pH was lowered to 6.5 using HCl or H2SO4 and no CO2, the same effects were observed. Also, local application of HCl or H2SO4 to the external surface of the cell soma elicited depolarization and spike discharge. When extracellular pH was held constant by continual titration, 5–50% CO2 had no effect. Intracellular pH was probably decreased at least one pH unit under these circumstances. Thus CO2 per se, decreased intracellular pH, and increased bicarbonate ion were without effect. It is concluded that CO2 acts solely through a decrease in extracellular pH.

Full Text

The Full Text of this article is available as a PDF (1.4 MB).

Selected References

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

  1. ADLER S., ROY A., RELMAN A. S. INTRACELLULAR ACID-BASE REGULATION. II. THE INTERACTION BETWEEN CO-2 TENSION AND EXTRACELLULAR BICARBONATE IN THE DETERMINATION OF MUSCLE CELL PH. J Clin Invest. 1965 Jan;44:21–30. doi: 10.1172/JCI105123. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. ADRIAN R. H. The effect of internal and external potassium concentration on the membrane potential of frog muscle. J Physiol. 1956 Sep 27;133(3):631–658. doi: 10.1113/jphysiol.1956.sp005615. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Alving B. O. Spontaneous activity in isolated somata of Aplysia pacemaker naurons. J Gen Physiol. 1968 Jan;51(1):29–45. doi: 10.1085/jgp.51.1.29. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Brown A. M., Sutton R. B., Walker J. L., Jr Increased chloride conductance as the proximate cause of hydrogen ion concentration effects in Aplysia neurons. J Gen Physiol. 1970 Nov;56(5):559–582. doi: 10.1085/jgp.56.5.559. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. CHALAZONITIS N. Effects of changes in Pco2 and Po2 on rhythmic potentials from giant neurons. Ann N Y Acad Sci. 1963 Jun 24;109:451–479. doi: 10.1111/j.1749-6632.1963.tb13480.x. [DOI] [PubMed] [Google Scholar]
  6. CONWAY E. J. Nature and significance of concentration relations of potassium and sodium ions in skeletal muscle. Physiol Rev. 1957 Jan;37(1):84–132. doi: 10.1152/physrev.1957.37.1.84. [DOI] [PubMed] [Google Scholar]
  7. Chalazonitis N., Takeuchi H. Application microélectrophorétique locale d'ions H et variations des paramètres bioélectriques de la membrane neuronique. C R Seances Soc Biol Fil. 1966;160(3):610–615. [PubMed] [Google Scholar]
  8. FURSHPAN E. J., POTTER D. D. Transmission at the giant motor synapses of the crayfish. J Physiol. 1959 Mar 3;145(2):289–325. doi: 10.1113/jphysiol.1959.sp006143. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. GRUNDFEST H. Ionic mechanisms in electrogenesis. Ann N Y Acad Sci. 1961 Sep 6;94:405–457. doi: 10.1111/j.1749-6632.1961.tb35554.x. [DOI] [PubMed] [Google Scholar]
  10. Geduldig D., Junge D. Sodium and calcium components of action potentials in the Aplysia giant neurone. J Physiol. 1968 Dec;199(2):347–365. doi: 10.1113/jphysiol.1968.sp008657. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. LING G., GERARD R. W. The normal membrane potential of frog sartorius fibers. J Cell Physiol. 1949 Dec;34(3):383–396. doi: 10.1002/jcp.1030340304. [DOI] [PubMed] [Google Scholar]
  12. MEVES H., VOLKNER K. G. Die Wirkung von CO2 auf das Ruhemembranpotential und die elektrischen Konstanten der quergestreiften Muskelfaser. Pflugers Arch. 1958;265(5):457–476. doi: 10.1007/BF00369773. [DOI] [PubMed] [Google Scholar]
  13. VON EULER C., SODERBERG U. Medullary chemosensitive receptors. J Physiol. 1952 Dec;118(4):545–554. doi: 10.1113/jphysiol.1952.sp004816. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. WADDELL W. J., BUTLER T. C. Calculation of intracellular pH from the distribution of 5,5-dimethyl-2,4-oxazolidinedione (DMO); application to skeletal muscle of the dog. J Clin Invest. 1959 May;38(5):720–729. doi: 10.1172/JCI103852. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Waddell W. J., Bates R. G. Intracellular pH. Physiol Rev. 1969 Apr;49(2):285–329. doi: 10.1152/physrev.1969.49.2.285. [DOI] [PubMed] [Google Scholar]
  16. Walker J. L., Jr, Brown A. M. Unified account of the variable effects of carbon dioxide on nerve cells. Science. 1970 Mar 13;167(3924):1502–1504. doi: 10.1126/science.167.3924.1502. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of General Physiology are provided here courtesy of The Rockefeller University Press

RESOURCES