Intrathecal neurokinin A facilitates the spinal nociceptive flexor reflex evoked by thermal and mechanical stimuli and synergistically interacts with substance P

Authors

  • X.-J. XU,

    1. Department of Clinical Physiology, Section of Clinical Neurophysiology, Karolinska Institute, Huddinge University Hospital, Huddinge, Sweden
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  • Z. WIESENFELD-HALLIN

    Corresponding author
    1. Department of Clinical Physiology, Section of Clinical Neurophysiology, Karolinska Institute, Huddinge University Hospital, Huddinge, Sweden
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Section of Clinical Neurophysiology, Huddinge University Hospital, S-141 86 Huddinge, Sweden.

Abstract

The neuropeptide neurokinin A was injected intrathecally and its effect on the spinal nocifensive flexor reflex was examined. The reflex, which was evoked by electrical, thermal or mechanical stimulation of the foot and was recorded from the ipsilateral hamstring muscles, was substantially facilitated by 7 pmol intrathecally injected neurokinin A. The facilitatory effect of neurokinin A to thermal stimulation was, however, significantly stronger than to electrical or mechanical stimuli. Furthermore, co-administration of neurokinin A with substance P induced a significant synergistic facilitation of the reflex. It is suggested that neurokinin A, like substance P, may be released in association with activation of polymodal C-nociceptors.

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