Distinct brainstem to spinal cord noradrenergic pathways inversely regulate spinal neuronal activity

Mateusz W. Kucharczyk*, Francesca Di Domenico, Kirsty Bannister

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)
33 Downloads (Pure)

Abstract

Brainstem to spinal cord noradrenergic pathways include a locus coeruleus origin projection and diffuse noxious inhibitory controls. While both pathways are traditionally viewed as exerting an inhibitory effect on spinal neuronal activity, the locus coeruleus was previously shown to have a facilitatory influence on thermal nocioception according to the subpopulation of coerulean neurons activated. Coupled with knowledge of its functional modular organisation and the fact that diffuse noxious inhibitory controls are not expressed in varied animal models of chronicity, we hypothesized a regulatory role for the locus coeruleus on non-coerulean, discrete noradrenergic cell group(s). We implemented locus coeruleus targeting strategies by microinjecting canine adenovirus encoding for channelrhodopsin-2 under a noradrenaline-specific promoter in the spinal cord (retrogradely labelling a coeruleospinal module) or the locus coeruleus itself (labelling the entire coerulean module). Coeruleospinal module optoactivation abolished diffuse noxious inhibitory controls (two-way ANOVA, P < 0.0001), which were still expressed following locus coeruleus neuronal ablation. We propose that the cerulean system interacts with, but does not directly govern, diffuse noxious inhibitory controls. This mechanism may underlie the role of the locus coeruleus as a 'chronic pain generator'. Pinpointing the functionality of discrete top-down pathways is crucial for understanding sensorimotor modulation in health and disease.

Original languageEnglish
Pages (from-to)2293-2300
Number of pages8
JournalBrain
Volume145
Issue number7
Early online date4 Mar 2022
DOIs
Publication statusPublished - 1 Jul 2022

Keywords

  • descending modulation
  • diffuse noxious inhibitory controls
  • locus coeruleus
  • noradrenaline
  • spinal wide dynamic range neurons

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