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Synaptic input from homonymous group I afferents in m. longissimus lumborum motoneurons in the L4 spinal segment in cats

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Abstract

We examined the relationship between input resistance and amplitude of monosynaptic and polysynaptic EPSPs produced by electrical stimulation of group I muscle afferents innervating the m. longissimus lumborum (Long) at different levels (L1–L4) in Long motoneurons in L4 spinal segments to obtain an insight into the neuronal control of trunk muscles. In the Long motoneuron pool, the amplitude of monosynaptic EPSP was shown to have a close relationship to input resistance. Furthermore, the relation between the amplitude of polysynaptic EPSP after stimulating Long nerves at L3 and input resistance was statistically significant, but the relation between EPSP amplitude evoked by stimulation of Long at L1 or L2 and input resistance was not statistically significant. Our findings suggest a position-dependent control of motoneuron activity by group I muscle afferents. The motoneuron activities carried out by monosynaptic pathways and polysynaptic pathways from adjacent spinal segments are dependent on the intrinsic properties of motoneurons (input resistance, etc.), while the motoneuron activities carried out by polysynaptic pathways from the far spinal segments have independent intrinsic properties.

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Acknowledgement

We are grateful for suggestions by Em. Professor Shigemi Mori of the National Institute for Physiological Science, Okazaki, Japan.

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Authors and Affiliations

  1. Department of Veterinary Physiology, Yamaguchi University, 753-8515, Yamaguchi City, Japan

    Junko Akatani & Naomi Wada

  2. Department of Central Nervous System, Tokyo Metropolitan Institute of Gerontology, 173-0015, Tokyo, Japan

    Kenro Kanda

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  1. Junko Akatani
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  2. Kenro Kanda
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  3. Naomi Wada
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Correspondence to Naomi Wada.

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Akatani, J., Kanda, K. & Wada, N. Synaptic input from homonymous group I afferents in m. longissimus lumborum motoneurons in the L4 spinal segment in cats. Exp Brain Res 156, 396–398 (2004). https://doi.org/10.1007/s00221-003-1819-4

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  • DOI: https://doi.org/10.1007/s00221-003-1819-4

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