TY - JOUR
T1 - Primary afferent and spinal cord expression of gastrin-releasing peptide: Message, protein and antibody concerns
AU - Solorzano, Carlos
AU - Villafuerte, David
AU - Meda, Karuna
AU - Cevikbas, Ferda
AU - Braz, Joao
AU - Sharif-Naeini, Reza
AU - Juarez-Salinas, Dina
AU - Llewellyn-Smith, Ida
AU - Guan, Zhonghui
AU - Basbaum, Allan
PY - 2015/1/14
Y1 - 2015/1/14
N2 - There is continuing controversy relating to the primary afferent neurotransmitter that conveys itch signals to the spinal cord. Here, we investigated the DRG and spinal cord expression of the putative primary afferent-derived “itch” neurotransmitter, gastrin-releasing peptide (GRP). Using ISH, qPCR, and immunohistochemistry, we conclude that GRPis expressed abundantly in spinal cord, but not in DR Gneurons. Titration of the most commonly used GRP antiserum in tissues from wild-type and GRP mutant mice indicates that the antiserum is only selective for GRP at high dilutions. Paralleling these observations, we found that a GRPeGFP transgenic reporter mouse has abundant expression in superficial dorsalhorn neurons, but not in the DRG. In contrast to previous studies, neither dorsal rhizotomy noran intrathecal injection of capsaicin, which completely eliminated spinal cord TRPV1-immunoreactive terminals, altered dorsal horn GRP immunoreactivity. Unexpectedly, however, peripheral nerve injury induced significant GRP expression in a heterogeneous population of DRG neurons. Finally, duallabeling and retrograde tracing studies showed that GRP-expressing neurons of the superficial dorsal horn are predominantly interneurons, that a small number coexpress protein kinase C gamma (PKCγ), but that none coexpress the GRP receptor (GRPR). Our studies support the view that pruritogens engage spinal cord “itch” circuits via excitatory superficial dorsal horn interneurons that express GRP and that likely target GRPR-expressing interneurons. The fact that peripheral nerve injury induced de novo GRP expressionin DRG neurons points to a novel contribution of this peptide to pruritoceptive processing in neuropathic itch conditions.
AB - There is continuing controversy relating to the primary afferent neurotransmitter that conveys itch signals to the spinal cord. Here, we investigated the DRG and spinal cord expression of the putative primary afferent-derived “itch” neurotransmitter, gastrin-releasing peptide (GRP). Using ISH, qPCR, and immunohistochemistry, we conclude that GRPis expressed abundantly in spinal cord, but not in DR Gneurons. Titration of the most commonly used GRP antiserum in tissues from wild-type and GRP mutant mice indicates that the antiserum is only selective for GRP at high dilutions. Paralleling these observations, we found that a GRPeGFP transgenic reporter mouse has abundant expression in superficial dorsalhorn neurons, but not in the DRG. In contrast to previous studies, neither dorsal rhizotomy noran intrathecal injection of capsaicin, which completely eliminated spinal cord TRPV1-immunoreactive terminals, altered dorsal horn GRP immunoreactivity. Unexpectedly, however, peripheral nerve injury induced significant GRP expression in a heterogeneous population of DRG neurons. Finally, duallabeling and retrograde tracing studies showed that GRP-expressing neurons of the superficial dorsal horn are predominantly interneurons, that a small number coexpress protein kinase C gamma (PKCγ), but that none coexpress the GRP receptor (GRPR). Our studies support the view that pruritogens engage spinal cord “itch” circuits via excitatory superficial dorsal horn interneurons that express GRP and that likely target GRPR-expressing interneurons. The fact that peripheral nerve injury induced de novo GRP expressionin DRG neurons points to a novel contribution of this peptide to pruritoceptive processing in neuropathic itch conditions.
KW - DRG
KW - GRP
KW - GRPR
KW - Itch
KW - Nerve injury
KW - Pain
UR - http://www.scopus.com/inward/record.url?scp=84920972659&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.2955-14.2015
DO - 10.1523/JNEUROSCI.2955-14.2015
M3 - Article
VL - 35
SP - 648
EP - 657
JO - Journal of Neuroscience
JF - Journal of Neuroscience
SN - 0270-6474
IS - 2
ER -