Expression of gastrin-releasing peptide by excitatory interneurons in the mouse superficial dorsal horn

Gutierrez-Mecinas, M. , Watanabe, M. and Todd, A. J. (2014) Expression of gastrin-releasing peptide by excitatory interneurons in the mouse superficial dorsal horn. Molecular Pain, 10, 79. (doi: 10.1186/1744-8069-10-79) (PMID:25496164) (PMCID:PMC4320531)

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Abstract

Background: Gastrin-releasing peptide (GRP) and its receptor have been shown to play an important role in the sensation of itch. However, although GRP immunoreactivity has been detected in the spinal dorsal horn, there is debate about whether this originates from primary afferents or local excitatory interneurons. We therefore examined the relation of GRP immunoreactivity to that seen with antibodies that label primary afferent or excitatory interneuron terminals. We tested the specificity of the GRP antibody by preincubating with peptides with which it could potentially cross-react. We also examined tissue from a mouse line in which enhanced green fluorescent protein (EGFP) is expressed under control of the GRP promoter.<p></p> Results: GRP immunoreactivity was seen in both primary afferent and non-primary glutamatergic axon terminals in the superficial dorsal horn. However, immunostaining was blocked by pre-incubation of the antibody with substance P, which is present at high levels in many nociceptive primary afferents. EGFP+ cells in the GRP-EGFP mouse did not express Pax2, and their axons contained the vesicular glutamate transporter 2 (VGLUT2), indicating that they are excitatory interneurons. In most cases, their axons were also GRP-immunoreactive. Multiple-labelling immunocytochemical studies indicated that these cells did not express either of the preprotachykinin peptides, and that they generally lacked protein kinase Cγ, which is expressed by a subset of the excitatory interneurons in this region.<p></p> Conclusions: These results show that GRP is expressed by a distinct population of excitatory interneurons in laminae I-II that are likely to be involved in the itch pathway. They also suggest that the GRP immunoreactivity seen in primary afferents in previous studies may have resulted from cross-reaction of the GRP antibody with substance P or the closely related peptide neurokinin A.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Todd, Professor Andrew and Gutierrez-Mecinas, Dr Maria
Authors: Gutierrez-Mecinas, M., Watanabe, M., and Todd, A. J.
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Journal Name:Molecular Pain
Publisher:BioMed Central
ISSN:1744-8069
ISSN (Online):1744-8069
Copyright Holders:Copyright © 2014 The Authors
First Published:First published in Molecular Pain 10:79
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