Abstract
Experiments were conducted on brain isolated from the frogRana ridibunda using a current chop technique of transmembrane polarization and discrete measurement of membrane potential by a single microelectrode during intervals between waves of current. It was found that the current-voltage relationship of the motorneuron is non-linear; i.e., membrane resistance decreases considerably in step with increased depolarizing current. After the initial reduction, membrane resistance began to climb back when a more protracted current lasting 1–2 min was applied; consequently membrane potential level shifted towards more positive values of +50 mV and above at current levels of 40–60 nA. It then became possible to bring about complete reversal of monosynaptic EPSP produced in the lumbar motoneurons by stimulation of the brainstem reticular formation or by microelectrode stimulation of the ventrolateral tract descending fibers and to measure reversal potential of these EPSP directly, without resorting to computing or extrapolation. Measurements varied mainly between 0 and −10 mV.
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Literature cited
A. Gutman, Nerve Cell Dendrites [in Russian], Mokslas, Vil'nyus (1984).
G. G. Kurchavyi, “Properties of excitatory postsynaptic currents in cat motoneurons,” Fiziol. Zh. SSSR,66, No. 22, 169–175 (1980).
G. T. Kurchavyi, M. V. Motorina, and A. I. Shapovalov, “Distribution of synaptic inputs on analogous motoneuron models,” Neirofiziologiya,5, No. 3, 289–297 (1973).
G. G. Kurchavyi and B. T. Ryabov, “Measurement of postsynaptic currents in frog motoneurons using techniques of single electrode voltage clamping,” Fiziol. Zh. SSSR,70, No. 1, 94–97 (1984).
A. I. Shapovalov, Postsynaptic Processes in Central Neurons [in Russian], in: A General Physiology of the Nervous System, Nauka, Leningrad, (1979).
A. I. Shapovalov and B. I. Shiryaev, “Ionic mechanisms underlying excitation of the neuronal postsynaptic membrane of the vertebrate central nervous system,” Dokl. Akad. Nauk. SSSR,225, No. 2, 477–479 (1975).
B. I. Shiryaev, Descending Synaptic Influences on Frog Motoneurons, Dissertation, Leningrad, (1972).
J. Eccles, Physiology of Synapses, Academic Press (1964).
T. Araki and C. A. Terzuolo, “Membrane currents in spinal motoneurones associated with action potential and synaptic activity,” J. Neurophysiol.,25, No. 6, 772–789 (1962).
W. H. Calvin, “Dendritic synapses and reversal potentials: theoretical implications of the view from the soma,” Exp. Neurol.,24, No. 3, 248–264 (1969).
J. S. Coombs, J. C. Eccles, and P. Fatt, “Excitatory synaptic action in motoneurones,” J. Physiol.,130, No. 2, 374–395 (1955).
F. R. Edwards, S. J. Redman, and B. Walmsley, “The effect of polarising currents on unitary Ia excitatory post-synaptic potentials evoked in spinal motoneurones,” J. Physiol.,259, 705–724 (1976).
I. Engberg and K. C. Marshall, “Reversal potential for Ia excitatory postsynaptic potentials in spinal motoneurones of cats,” Neuroscience,4, No. 11, 1583–1591 (1979).
A. S. Finkel and S. J. Redman, “The synaptic current evoked in cat spinal motoneurones by impulses in single group Ia axons,” J. Physiol.,342, 615–632 (1983).
P. G. Flatman, I. Engberg, and J. D. S. Lambert, “Reversibility of Ia EPSP investigated with intracellularly iontophoresed QX-22,” J. Neurophysiol.,48, No. 2, 419–430 (1982).
M. Ito and T. Oshima, “Electrical behavior of the motoneurone membrane during intracellularly applied current steps,” J. Physiol.,180, No. 3, 607–635 (1965).
K. Kuba and S. Nishi, “Characteristics of fast excitatory postsynaptic current in bull frog sympathetic ganglion cells,” Pflügers Arch.,378, No. 2, 205–212 (1979).
W. Rall, R. E. Burke, T. G. Smith,et al., “Dendritic location of synapses and possible mechanisms for the monosynaptic EPSP in motoneurones,” J. Neurophysiol.,30, No. 5, 1169–1193 (1967).
A. I. Shapovalov and g. G. Kurchavyi, “Effects of transmembrane polarization and TEA injection on monosynaptic actions from motor cortex, red nucleus and group Ia afferents on lumbar motoneurones in the monkey,” Brain Res.,82, No. 1, 47–67 (1974).
A. I. Shapovalov, B. I. Shiriaev, and A. A. Velumian, “Mechanisms of postsynaptic excitation in amphibian motoneurones,” J. Physiol.,279, 437–455 (1978).
R. Werman and P. L. Carlen, “Unusual behaviour of the Ia EPSP in cat spinal motoneurones,” Brain Res.,112, No. 2, 395–401 (1976).
W. A. Wilson and M. M. Goldner, “Voltage clamping with single microelectrodes,” J. Neurobiol.,6, No. 4, 411–422 (1975).
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I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 18, No. 4, pp. 534–542, July–August, 1986.
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Kalinina, N.I., Kurchavyi, G.G. & Ryabov, V.T. Reversal potential for monosynaptic EPSP in frog motoneurons. Neurophysiology 18, 393–401 (1986). https://doi.org/10.1007/BF01052810
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DOI: https://doi.org/10.1007/BF01052810