Differential presynaptic control of the synaptic effectiveness of cutaneous afferents evidenced by effects produced by acute nerve section

Authors

  • P. Rudomin,

    1. Department of Physiology, Biophysics and Neurosciences, Center of Research and Advanced Studies of the Instituto Politécnico Nacional, México
    2. Colegio Nacional, México
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  • I. Jiménez,

    1. Department of Physiology, Biophysics and Neurosciences, Center of Research and Advanced Studies of the Instituto Politécnico Nacional, México
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  • D. Chávez

    1. Department of Physiology, Biophysics and Neurosciences, Center of Research and Advanced Studies of the Instituto Politécnico Nacional, México
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P. Rudomin: Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y de Estudios Avanzados, del Instituto Politécnico Nacional, Avenida Instituto Politécnico Nacional 2408, México DF 07360, México. Email: rudomin@fisio.cinvestav.mx

Key points

  • • We investigated, in the anaesthetized cat, the effects of acute section of the saphenous and superficial peroneal nerves on the synaptic effectiveness of the sural nerve afferents.
  • • We found that acute section of these nerves produced a long-lasting increase of the sural-evoked field potentials. At the same time, sural afferents ending within Rexed's laminae III–IV showed a reduced tonic primary afferent depolarization, while sural afferents projecting deeper into the dorsal horn (Rexed's laminae V–VI) instead showed increased tonic primary afferent depolarization.
  • • It is suggested that a differential control of the synaptic effectiveness of the low-threshold cutaneous afferents according to their sites of termination within the dorsal horn provides means for a selective processing of sensory information in response to tactile and nociceptive stimulation or during the execution of different motor tasks.

Abstract  In the anaesthetized cat, the acute section of the saphenous (Saph) and/or the superficial peroneal (SP) nerves was found to produce a long-lasting increase of the field potentials generated in the dorsal horn by stimulation of the medial branch of the sural (mSU) nerve. This facilitation was associated with changes in the level of the tonic primary afferent depolarization (PAD) of the mSU intraspinal terminals. The mSU afferent fibres projecting into Rexed's laminae III–IV were subjected to a tonic PAD that was reduced by the acute section of the SP and/or the Saph nerves. The mSU afferents projecting deeper into the dorsal horn (Rexed's laminae V–VI) were instead subjected to a tonic PAD that was increased after Saph and SP acute nerve section. A differential control of the synaptic effectiveness of the low-threshold cutaneous afferents according to their sites of termination within the dorsal horn is envisaged as a mechanism that allows selective processing of sensory information in response to tactile and nociceptive stimulation or during the execution of different motor tasks.

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