Lamina-specific population encoding of cutaneous signals in the spinal dorsal horn using multi-electrode arrays

Greenspon, Charles M.; Battell, Emma E.; Devonshire, Ian M.; Donaldson, Lucy F.; Chapman, Victoria; Hathway, Gareth J.

Abstract

The dorsal spinal cord (DH) is a complex laminar structure integrating peripheral signals into the central nervous system. Spinal somatosensory processing is commonly measured electrophysiologically in vivo by recording the activity of individual Wide Dynamic Range neurons in the deep DH and extrapolating their behaviour to all cells in every lamina. This fails to account for the specialised processes that occur in each lamina and the considerable heterogeneity in cellular phenotype within and between laminae. Here we overcome this oversimplification by employing linear multi‐electrode arrays (MEAs) in the DH of anaesthetized rats to simultaneously measure activity across all laminae. The MEAs, comprised of 16‐channels, were inserted into the lumbar dorsal horn and peripheral neurones activated electrically via transcutaneous electrodes and ethologically with von Frey hairs (vFh) or an aluminium heating block. Ascending electrical stimuli showed fibre thresholds with distinct dorso‐ventral innervation profiles. Wind up was observed across the DH during the C‐fibre and post‐discharge latencies following 0.5Hz stimulation. Intrathecal application of morphine (5ng/50ul) significantly reduced Aδ and C‐fibre evoked activity in deep and superficial DH. Light vFhs (≤10g) predominantly activated intermediate and deep laminae whereas noxious vFh (26g) also activated the superficial laminae. Noxious heat (55°C) induced significantly greater activity in the superficial and deep laminae than the innocuous control (30°C). The application of these arrays produced the first description of the processing of innocuous and noxious stimuli throughout the intact DH.

Citation

Greenspon, C. M., Battell, E. E., Devonshire, I. M., Donaldson, L. F., Chapman, V., & Hathway, G. J. (2019). Lamina-specific population encoding of cutaneous signals in the spinal dorsal horn using multi-electrode arrays. Journal of Physiology, 597(2), 377-397. https://doi.org/10.1113/jp277036

• Journal Article Type: Article
• Acceptance Date: Oct 31, 2018
• Online Publication Date: Nov 3, 2018
• Publication Date: Jan 15, 2019
• Deposit Date: Nov 21, 2018
• Publicly Available Date: Nov 21, 2018
• Journal: The Journal of Physiology
• Print ISSN: 0022-3751
• Electronic ISSN: 1469-7793
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 597
• Issue: 2
• Pages: 377-397
• DOI: https://doi.org/10.1113/jp277036
• Public URL: https://nottingham-repository.worktribe.com/output/1295172
• Publisher URL: https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/JP277036