Immunostaining for Homer reveals the majority of excitatory synapses in laminae I-III of the mouse spinal dorsal horn

Gutierrez-Mecinas, M. , Kuehn, E. D., Abraira, V. E., Polgár, E., Watanabe, M. and Todd, A. J. (2016) Immunostaining for Homer reveals the majority of excitatory synapses in laminae I-III of the mouse spinal dorsal horn. Neuroscience, 329, pp. 171-181. (doi: 10.1016/j.neuroscience.2016.05.009) (PMID:27185486) (PMCID:PMC4915440)

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The spinal dorsal horn processes somatosensory information before conveying it to the brain. The neuronal organization of the dorsal horn is still poorly understood, although recent studies have defined several distinct populations among the interneurons, which account for most of its constituent neurons. All primary afferents, and the great majority of neurons in laminae I–III are glutamatergic, and a major factor limiting our understanding of the synaptic circuitry has been the difficulty in identifying glutamatergic synapses with light microscopy. Although there are numerous potential targets for antibodies, these are difficult to visualize with immunocytochemistry, because of protein cross-linking following tissue fixation. Although this can be overcome by antigen retrieval methods, these lead to difficulty in detecting other antigens. The aim of this study was to test whether the postsynaptic protein Homer can be used to reveal glutamatergic synapses in the dorsal horn. Immunostaining for Homer gave punctate labeling when viewed by confocal microscopy, and this was restricted to synapses at the ultrastructural level. We found that Homer puncta were colocalized with the AMPA receptor GluR2 subunit, but not with the inhibitory synapse-associated protein gephyrin. We also examined several populations of glutamatergic axons and found that the great majority of boutons were in contact with at least one Homer punctum. These results suggest that Homer antibodies can be used to reveal the great majority of glutamatergic synapses without antigen retrieval. This will be of considerable value in tracing synaptic circuits, and also in investigating plasticity of glutamatergic synapses in pain states.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Beresford-Polgar, Dr Erika and Todd, Professor Andrew and Gutierrez-Mecinas, Dr Maria
Authors: Gutierrez-Mecinas, M., Kuehn, E. D., Abraira, V. E., Polgár, E., Watanabe, M., and Todd, A. J.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Neuroscience
ISSN (Online):1873-7544
Published Online:13 May 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Neuroscience 329:171-181
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
644161Defining pain circuitry in health and diseaseAndrew ToddWellcome Trust (WELLCOME)102645/Z/13/ZINP - CENTRE FOR NEUROSCIENCE
627371Spinal inhibitory interneurons that suppress itchAndrew ToddMedical Research Council (MRC)MR/L003430/1INP - CENTRE FOR NEUROSCIENCE