Periaqueductal grey cyclooxygenase-dependent facilitation of C-nociceptive drive and encoding in dorsal horn neurons in the rat

J Lianne Leith, Alex W Wilson, Hao-Jun You, Bridget M Lumb, Lucy F Donaldson

Research output: Contribution to journalArticle (Academic Journal)

5 Citations (Scopus)

Abstract

The experience of pain is strongly affected by descending control systems originating in the brainstem ventrolateral periaqueductal grey (VL-PAG), which control the spinal processing of nociceptive information. A- and C-fibre nociceptors detect noxious stimulation, and have distinct and independent contributions to both the perception of pain quality (fast and slow pain respectively), and to the development of chronic pain. Evidence suggests a separation in the central processing of information arising from A- versus C-nociceptors; for example, inhibition of the cyclooxygenase-1-prostaglandin system within the VL-PAG alters spinal nociceptive reflexes evoked by C-nociceptor input in vivo via descending pathways, leaving A-nociceptor-evoked reflexes largely unaffected. As the spinal neuronal mechanisms underlying these different responses remain unknown, we determined the effect of inhibition of VL-PAG cyclooxygenase-1 on dorsal horn wide-dynamic-range neurons evoked by C- versus A-nociceptor activation. Inhibition of VL-PAG cyclooxygenase-1 in anaesthetised rats increased firing thresholds of lamina IV-V wide-dynamic-range dorsal horn neurons in response to both A- and C-nociceptor stimulation. Importantly, wide-dynamic-range dorsal horn neurons continued to faithfully encode A-nociceptive information, even after VL-PAG cyclooxygenase-1 inhibition, whereas in contrast, the encoding of C-nociceptor information by wide-dynamic-range spinal neurons was significantly disrupted. Dorsal horn neurons with stronger C-nociceptor input were affected by cyclooxygenase-1 inhibition to a greater extent than those with weak C-fibre input. These data show that the gain and contrast of C-nociceptive information processed in individual wide-dynamic-range dorsal horn neurons is modulated by prostanergic descending control mechanisms in the ventrolateral periaqueductal grey. This article is protected by copyright. All rights reserved.

Original languageEnglish
Pages (from-to)5093-5107
JournalJournal of Physiology
Volume592
DOIs
Publication statusPublished - 19 Sep 2014

Bibliographical note

This article is protected by copyright. All rights reserved.

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