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Journal of Comparative Physiology A

, Volume 155, Issue 2, pp 197–208 | Cite as

Ionic bases of action potentials in identified flatworm neurones

  • Larry Keenan
  • Harold Koopowitz
Article

Summary

The ionic bases for generation of action potentials in three types of identified multimodal neurones of the brain ofNotoplana acticola, a polyclad flatworm, were studied. The action potentials were generated spontaneously, in response to water-borne vibrations, or by intracellularly injected current pulses. At least three components comprise the depolarizing excitable phase of the action potentials: (a) a rapidly inactivating TTXsensitive Na+ component (Fig. 2); (b) a Ca++ component that is unmasked by intracellular TEA+ (Figs. 4, 6, 7); (c) a TTX-resistant Na+ component (Fig. 8). Two K+ currents appear to account for the repolarization phase of the action potentials: (a) a rapid K+ current that is blocked by intracellular TEA+ (Figs. 4, 7, 8) and (b) a Ca++ -activated K+ conductance that is blocked by Ca++ and Ba++ (Fig. 6). Ionic mechanisms in the generation of action potentials in the central multimodal neurones ofNotoplana pharmacologically resemble those in higher metazoans.

Keywords

Current Pulse Ionic Mechanism Ionic Base Repolarization Phase Excitable Phase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

TTX

tetrodotoxin

TEA+

tetraethylammonium ion

LY

lucifer yellow

HRP

horseradish peroxidase

BRA

bilaterally reciprocally arrayed neurons

SC

single contralaterally projecting

SIC

single ipsilaterally and contralaterally projecting neurons

HAP

hyperpolarizing after potential

AHP

after hyperpolarization

EGTA

ethyleneglycol-bis-(β-amino-ethyl ester) N,N′-tetra-acetic acid

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References

  1. Adams P (1982) Voltage-dependent conductances of vertebrate neurons. TINS 5:116–119Google Scholar
  2. Adams DJ, Smith SJ, Thompson SH (1980) Ionic currents in molluscan soma. Annu Rev Neurosci 3:141–165Google Scholar
  3. Anderson PAV (1979) Ionic basis of action potentials and bursting activity in the hydromedusan jellyfish,Polyorchis penicillatus. J Exp Biol 78:859–872Google Scholar
  4. Armstrong CN, Binstock L (1965) Anomolous rectification in the squid giant axon injected with tetraethylammonium chloride. J Gen Physiol 48:859–872Google Scholar
  5. Bernardo KG, Stone G, Koopowitz H (1977) Primitive nervous systems: peripheral habituaton in decerebrate polyclad flatworms. J Neurobiol 8:141–150Google Scholar
  6. Byre JH, Koester J (1980) Neural mechanisms underlying stimulus control of ink release inAplysia. In: Koester J, Byrne JH (eds) Molluscan nerve cells from biophysics to behavior. Cold Spring Harbor Symp Quant Biol 1, pp 157–167Google Scholar
  7. Cahalan MD (1980) Molecular properties of sodium channels in excitable membranes. In: Cotman CW, Poste G, Nicholson GL (eds) The cell and neuronal function, Elvesier/North Holland and Biomedical Press, New York, pp 1–47Google Scholar
  8. Connor JA, Stevens CF (1971a) Inward and delayed outward membrane currents in isolated neural somata under voltage clamp. J Physiol (London) 213:21–30Google Scholar
  9. Connor JA, Stevens CF (1971b) Voltage clamp studies of a transient outward membrane current in gastropod neural somata. J Physiol (London) 213:21–30Google Scholar
  10. Crill WE, Schwindt PC (1983) Active currents in mammalian central neurons. TINS 6:236–240Google Scholar
  11. Eckert R, Lux HD (1976) A voltage-sensitive persistent calcium conduction in neuronal somata ofHelix. J Physiol (London) 254:129–151Google Scholar
  12. Frankenhaeuser B, Huxley AF (1964) The action potential in the myelinated nerve fiber ofXenopus laevis as computed on the basis of voltage clamp data. J Physiol (London) 171:302–315Google Scholar
  13. Geduldig D, Gruener R (1970) Voltage clamp of theAplysia giant neuron: early sodium and calcium current. J Physiol (London) 211:217–244Google Scholar
  14. Goodman CS, Spitzer NC (1981) The mature electrical properties of identified neurons in grasshopper embryos. J Physiol (London) 313:369–384Google Scholar
  15. Gorman ALF, Thomas MV (1981) Potassium conductance and internal calcium accumulation in a molluscan neurone. J Physiol (London) 308:287–313Google Scholar
  16. Gorman ALF, Hermann A, Thomas MV (1980) The neuronal pacemake cycle. In: Koester J, Byrne JH (eds) Molluscan nerve cells: from biophysics to behavior. Cold Spring Harbor Symp Quant Biol 1, pp 169–180Google Scholar
  17. Hagiwara S (1975) Ca-dependent action potential. In: Eisenmann G (ed) Membranes — A series of advances, vol 3. Dekker, New York, pp 359–382Google Scholar
  18. Herman A, Gorman ALF (1981) Effects of tetra-ethylammonium on potassium currents in molluscan neuron. J Gen Physiol 78:87–110Google Scholar
  19. Heyer CD, Lux HD (1976) Properties of a facilitating calcium current in pacemaker neurones of the snail,Helix pomatia. J Physiol (London) 262:319–348Google Scholar
  20. Hille B (1977) Ionic basis of resting and action potentials. In: Kandel ER (ed) Cellular biology of neurons, Part I, vol I. The handbook of physiology, Williams and Wilkins Co., Baltimore, MD, pp 99–136Google Scholar
  21. Hodgkin AL, Huxley AF (1952b) A quantitative description of membrane current and its application to conduction and excitation in nerve. J Physiol (London) 117:500–544Google Scholar
  22. Keenan L, Koopowitz H (1981) Tetrodotoxin-sensitive action potentials from the brain of the polyclad flatwormNotoplana acticola. J Exp Zool 215:209–213Google Scholar
  23. Keenan CL, Koopowitz H (1983a) Primitive nervous systems: Characteristics of identified multimodal neurones in the brain of the polyclad flatworm,Notoplana acticola. I. Morphology. PhD Dissertation, Univ of California Section I.Google Scholar
  24. Keenan CL, Koopowitz H (1983 b) Primitive neurones in the brain of the polyclad flatworm,Notoplana acticola. II. Electrophysiological responses. PhD Dissertation, Section II, Univ IrvineGoogle Scholar
  25. Koopowitz H, Keenan CL (1982) The primitive brains of Platyhelminthes. TINS 5:77–79Google Scholar
  26. Llinás RS, Sugimori M (1978) Dendritic calcium spiking in mammalian Purkinje cells: in vitro study of its function and development. Neurosci Abstr 4:66Google Scholar
  27. Matsuda Y, Yoshida S, Yonezawa I (1978) Tetrodotoxin sensitivity and Ca component of action potentials of mouse dorsal root ganglion cells cultured in vitro. Brain Res 154:69–82Google Scholar
  28. McLachlan EM (1977) The effects of strontium and barium ions at synapses in sympathetic ganglia. J Physiol (London) 267:497–518Google Scholar
  29. Meech RW (1974) The sensitivity ofHelix aspersa neurons to injected calcium ions. J Physiol (London) 237:259–277Google Scholar
  30. Meech RW (1978) Calcium-dependent potassium activation in nervous tissues. Annu Rev Biophys Bioeng 7:1–18Google Scholar
  31. Narahashi T (1974) Chemicals as tools in the study of excitable membranes. Physiol Rev 54:813–889Google Scholar
  32. Narahashi T, Moore JW, Scott WR (1964) Tetrodotoxin blockage of sodium conductance increase in lobster giant axons. J Gen Physiol 47:965–974Google Scholar
  33. Siegel JN (1979) Behavioral function of the reticular formation. Brain Ress Rev 1:69–105Google Scholar
  34. Solon MH, Koopowitz H (1982) Multimodal interneurons in the polyclad flatworm,Alloeoplana californica. J Comp Physiol 147:171–178Google Scholar
  35. Spencer AN, Satterlie RA (1981) The action potential and contraction in subumbrellar swimming muscle ofPolyorchis pencillatus (Hydromedusae). J Comp Physiol 144:401–407Google Scholar
  36. Stevens CF (1980) Ionic channels in neuromembranes: methods for studying their properties. In: Koester J, Byrne JH (eds) Molluscan nerve cells: From biophysics to behavior, Cold Spring Harbor Symp Quant Biol 1, pp 11–31Google Scholar
  37. Thompson SH, Aldrich RW (1980) Membrane potassium channels. In: Cotman CW, Poste G, Nicholson GL (eds) The cell surface and neuronal function, Elsevier/North-Holland Biomedical Press, New York, pp 49–85Google Scholar
  38. Tillotson D (1979) Characterization of calcium conductance depends on entry of Ca ions in molluscan nerves. Proc Natl Acad Sci USA 76:1497Google Scholar

Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • Larry Keenan
    • 1
  • Harold Koopowitz
    • 1
  1. 1.Developmental and Cell Biology DepartmentUniversity of CaliforniaIrvineUSA

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