Co‐localization of nociceptive markers in the lumbar dorsal root ganglion and spinal cord of dromedary camel. Issue 17 (24th September 2021)

• Record Type: Journal Article
• Authors: Javed, Hayate; Rehmathulla, Sumisha; Tariq, Saeed; Ali, Mahmoud A.; Emerald, Bright Starling; Shehab, Safa
• Is Part Of: Journal of comparative neurology. Volume 529:Issue 17(2021)
• Page Start: 3710
• Page End: 3725
• Publication Date: 2021-09-24
• Subjects: dromedary camel -- IB4 -- CGRP -- TRPV1 -- NPY -- CCK -- NOS -- DRG -- spinal cord -- AB_725809 -- AB_91824 -- AB_2315370 -- AB_51814; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.25240
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: Nociceptive markers in mice have been identified in two distinct peptidergic and nonpeptidergic neurons in the dorsal root ganglion (DRG) and distributed in different laminae of the dorsal horn of the spinal cord. Recently, however, a study in humans showed a significant overlapping in these two populations. In this study, we investigated the distribution of various nociceptive markers in the lumbar DRG and spinal cord of the dromedary camel. Immunohistochemical data showed a remarkable percentage of total neurons in the DRG expressed IB4 binding (54.5%), calcitonin gene‐related peptide (CGRP; 49.5%), transient receptor potential vanilloid 1 (TRPV1; 48.2%), and nitric oxide synthase (NOS; 30.6%). The co‐localization data showed that 89.6% and 74.0% of CGRP‐ and TRPV1‐labeled neurons, respectively, were IB4 positive. In addition, 61.6% and 84.2% of TRPV1‐ and NOS‐immunoreactive neurons, respectively, were also co‐localized with CGRP. The distribution of IB4, CGRP, TRPV1, substance P, and NOS immunoreactivities in the spinal cord were observed in lamina I and outer lamina II (IIo). Quantitative data showed that 82.4% of IB4‐positive nerve terminals in laminae I and IIo were co‐localized with CGRP, and 86.0% of CGRP‐labeled terminals were co‐localized with IB4. Similarly, 85.1% of NOS‐labeled nerve terminals were co‐localized with CGRP. No neuropeptide Y (NPY) or cholecystokinin (CCK) immunoreactivities were detected in the DRG, and no co‐localization between IB4, NPY, and CCK were observed in the spinal cord. Our results demonstrate marked convergence of nociceptive markers in the primary afferent neurons in camels, which is similar to humans rather than the mouse. The data also emphasizes the importance of interspecies differences when selecting ideal animal models for studying nociception and treating chronic pain. Abstract : Confocal images showing marked co‐localization of TRPV1, IB4, and CGRP in one section (a–d) and NOS, IB4, and CGRP in another section (e–h) of the camel DRG.