Functional differences between neurochemically defined populations of inhibitory interneurons in the rat spinal dorsal horn

Polgár, E., Sardella, T.C.P., Tiong, S.Y.X., Locke, S., Watanabe, M. and Todd, A.J. (2013) Functional differences between neurochemically defined populations of inhibitory interneurons in the rat spinal dorsal horn. Pain, 154(12), pp. 2606-2615. (doi: 10.1016/j.pain.2013.05.001)

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Abstract

In order to understand how nociceptive information is processed in the spinal dorsal horn we need to unravel the complex synaptic circuits involving interneurons, which constitute the vast majority of the neurons in laminae I–III. The main limitation has been the difficulty in defining functional populations among these cells. We have recently identified 4 nonoverlapping classes of inhibitory interneuron, defined by expression of galanin, neuropeptide Y (NPY), neuronal nitric oxide synthase (nNOS) and parvalbumin, in the rat spinal cord. In this study we demonstrated that these form distinct functional populations that differ in terms of sst2A receptor expression and in their responses to painful stimulation. The sst2A receptor was expressed by nearly all of the nNOS- and galanin-containing inhibitory interneurons but by few of those with NPY and none of the parvalbumin cells. Many galanin- and NPY-containing cells exhibited phosphorylated extracellular signal-regulated kinases (pERK) after mechanical, thermal or chemical noxious stimuli, but very few nNOS-containing cells expressed pERK after any of these stimuli. However, many nNOS-positive inhibitory interneurons up-regulated Fos after noxious thermal stimulation or injection of formalin, but not after capsaicin injection; nor did parvalbumin cells express either activity-dependent marker after any of these stimuli. These results suggest that interneurons belonging to the NPY, nNOS and galanin populations are involved in attenuating pain, and for NPY and nNOS cells this is likely to result from direct inhibition of nociceptive projection neurons. They also suggest that the nociceptive inputs to the nNOS cells differ from those to the galanin and NPY populations.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sardella, Dr Thomas and Beresford-Polgar, Dr Erika and Todd, Professor Andrew
Authors: Polgár, E., Sardella, T.C.P., Tiong, S.Y.X., Locke, S., Watanabe, M., and Todd, A.J.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Pain
ISSN:0304-3959
ISSN (Online):1872-6623
Copyright Holders:Copyright © 2013 The Authors
First Published:First published in Pain 154(12):2606-2615
Publisher Policy:Reproduced under a Creative Commons License

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