Projection neurons in lamina III of the rat spinal cord are selectively innervated by local dynorphin-containing excitatory neurons

Baseer, N., Watanabe, M., Furuta, T., Kaneko, T. and Todd, A.J. (2012) Projection neurons in lamina III of the rat spinal cord are selectively innervated by local dynorphin-containing excitatory neurons. Journal of Neuroscience, 32(34), pp. 11854-11863. (doi: 10.1523/JNEUROSCI.2707-12.2012)

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Abstract

Large projection neurons in lamina III of the rat spinal cord that express the neurokinin 1 receptor are densely innervated by peptidergic primary afferent nociceptors and more sparsely by low-threshold myelinated afferents. However, we know little about their input from other glutamatergic neurons. Here we show that these cells receive numerous contacts from nonprimary boutons that express the vesicular glutamate transporter 2 (VGLUT2), and form asymmetrical synapses on their dendrites and cell bodies. These synapses are significantly smaller than those formed by peptidergic afferents, but provide a substantial proportion of the glutamatergic synapses that the cells receive (over a third of those in laminae I–II and half of those in deeper laminae). Surprisingly, although the dynorphin precursor preprodynorphin (PPD) was only present in 4–7% of VGLUT2 boutons in laminae I–IV, it was found in 58% of the VGLUT2 boutons that contacted these cells. This indicates a highly selective targeting of the lamina III projection cells by glutamatergic neurons that express PPD, and these are likely to correspond to local neurons (interneurons and possibly projection cells). Since many PPD-expressing dorsal horn neurons respond to noxious stimulation, this suggests that the lamina III projection cells receive powerful monosynaptic and polysynaptic nociceptive input. Excitatory interneurons in the dorsal horn have been shown to possess IA currents, which limit their excitability and can underlie a form of activity-dependent intrinsic plasticity. It is therefore likely that polysynaptic inputs to the lamina III projection neurons are recruited during the development of chronic pain states.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Todd, Professor Andrew
Authors: Baseer, N., Watanabe, M., Furuta, T., Kaneko, T., and Todd, A.J.
Subjects:Q Science > QH Natural history > QH301 Biology
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Research Group:Spinal Cord group
Journal Name:Journal of Neuroscience
Publisher:The Society for Neuroscience
ISSN:0270-6474
ISSN (Online):1529-2401
Published Online:12 July 2012
Copyright Holders:Copyright © 2012 The Authors
First Published:First published in Journal of Neuroscience 32(34):11854-11863
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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