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Journal of Experimental Biology, Vol 175, Issue 1 59-87, Copyright © 1993 by Company of Biologists
JOURNAL ARTICLES |
LE Moore, RH Hill and S Grillner
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77550.
1. Voltage and current-clamp steps were added to a sum of sine waves to measure the tetrodotoxin-insensitive membrane properties of neurons in the intact lamprey spinal cord. A systems analysis in the frequency domain was carried out on two types of cells that have very different morphologies in order to investigate the structural dependence of their electrophysiological properties. The method explicitly takes into account the geometrical shapes of (i) nearly spherical dorsal cells with one or two processes and (ii) motoneurons and interneurons that have branched dendritic structures. Impedance functions were analysed to obtain the cable properties of these in situ neurons. These measurements show that branched neurons are not isopotential and, therefore, a conventional voltage-clamp analysis is not valid. 2. The electrophysiological data from branched neurons were curve-fitted with a lumped soma-equivalent cylinder model consisting of eight equal compartments coupled to an isopotential cell body to obtain membrane parameters for both passive and active properties. The analysis provides a quantitative description of both the passive electrical properties imposed by the geometrical structure of neurons and the voltage-dependent ionic conductances determined by ion channel kinetics. The model fitting of dorsal cells was dominated by a one-compartment resistance and capacitance in parallel (RC) corresponding to the spherical, non-branched shape of these cells. Branched neurons required a model that contained both an RC compartment and a cable that reflected the structure of the cells. At rest, the electrotonic length of the cable was about two. Uniformly distributed voltage-dependent ionic conductance sites were adequate to describe the data at different membrane potentials. 3. The frequency domain admittance method in conjunction with a step voltage clamp was used to control and measure the oscillatory behavior induced by N-methyl-D-aspartate (NMDA) on lamprey spinal cord neurons. Voltage-clamp currents and impedance functions were measured at different membrane potentials. The impedance functions had a voltage-dependent resonance and phase shift characteristic of a negative conductance. These measurements provide a quantitative analysis of the conductances induced by NMDA in central neurons of the lamprey spinal cord and directly establish the basis of the non-linear oscillatory behavior previously observed in the presence of NMDA. NMDA was shown specifically to activate a negative and a positive conductance, both of which were markedly affected by the membrane potential. It is shown that the net current in the presence of NMDA must be considered as the algebraic sum of currents in opposite directions.(ABSTRACT TRUNCATED AT 400 WORDS)
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  A. Uno, E. Idoux, M. Beraneck, P.-P. Vidal, L. E. Moore, V. J. Wilson, and N. Vibert Static and Dynamic Membrane Properties of Lateral Vestibular Nucleus Neurons in Guinea Pig Brain Stem Slices J Neurophysiol, September 1, 2003; 90(3): 1689 - 1703. [Abstract] [Full Text] [PDF]
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M. Beraneck, M. Hachemaoui, E. Idoux, L. Ris, A. Uno, E. Godaux, P.-P. Vidal, L. E. Moore, and N. Vibert Long-Term Plasticity of Ipsilesional Medial Vestibular Nucleus Neurons After Unilateral Labyrinthectomy J Neurophysiol, July 1, 2003; 90(1): 184 - 203. [Abstract] [Full Text] [PDF]
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 S. Alford, E. Schwartz, and G. V. Di Prisco The Pharmacology of Vertebrate Spinal Central Pattern Generators Neuroscientist, June 1, 2003; 9(3): 217 - 228. [Abstract] [PDF]
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B. S. Mleux and L. E. Moore Firing Properties and Electrotonic Structure of Xenopus Larval Spinal Neurons J Neurophysiol, March 1, 2000; 83(3): 1366 - 1380. [Abstract] [Full Text] [PDF]
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B. S. Mleux and L. E. Moore Active Dendritic Membrane Properties of Xenopus Larval Spinal Neurons Analyzed With a Whole Cell Soma Voltage Clamp J Neurophysiol, March 1, 2000; 83(3): 1381 - 1393. [Abstract] [Full Text] [PDF]
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 L. E. Moore, N. Chub, J. Tabak, and M. O'Donovan NMDA-Induced Dendritic Oscillations during a Soma Voltage Clamp of Chick Spinal Neurons J. Neurosci., October 1, 1999; 19(19): 8271 - 8280. [Abstract] [Full Text] [PDF]
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L. Prime, Y. Pichon, and L. E. Moore N-Methyl-D-Aspartate-Induced Oscillations in Whole Cell Clamped Neurons From the Isolated Spinal Cord of Xenopus laevis Embryos J Neurophysiol, August 1, 1999; 82(2): 1069 - 1073. [Abstract] [Full Text] [PDF]
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J. T. Buchanan Commissural Interneurons in Rhythm Generation and Intersegmental Coupling in the Lamprey Spinal Cord J Neurophysiol, May 1, 1999; 81(5): 2037 - 2045. [Abstract] [Full Text] [PDF]
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