Cable properties of a straight neurite of a leech neuron probed by a voltage-sensitive dye.
We measured a time-resolved map of electrical activity in a thin straight neurite (1.5 microns thick, 500 microns long) at a resolution of 8 microns and 0.4 ms. The neurite was obtained by guided outgrowth of an identified neuron of the leech on lanes of extracellular matrix protein. The electrical signals were detected by a fluorescent voltage-sensitive dye. We observed the voltage that was caused by an action potential elicited at the soma and by a Gaussian hyperpolarization induced at the soma, respectively. We compared the data with numerical solutions of the cable equation using the Hodgkin-Huxley parametrization. We could attribute the experimental results of depolarization and of hyperpolarization to the propagation of an action potential along an "active" cable and to the spread along a "passive" cable, respectively, if we assigned rather high specific resistances to the cytoplasm (RI = 250 omega.cm) and to the membrane (RM = 22 k omega.cm2). This assignment explained the slow velocity of 150 microns/ms of a pulse by active propagation and the limited range of 200 microns of a pulse by passive spread.
Fromherz
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Abteilung Biophysik der Universität Ulm, Germany.
Müller
C O
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D000200:Action Potentials; D000818:Animals; D004558:Electric Stimulation; D016326:Extracellular Matrix Proteins; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D007865:Leeches; D008433:Mathematics; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D008959:Models, Neurological; D016501:Neurites / Q000502:physiology* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011726:Pyridinium Compounds; D013343:Styrenes
D016326:Extracellular Matrix Proteins; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D013343:Styrenes; C070534:RH 421