Background & Aims
Understanding the development and maintenance of pathological pain is critical for the discovery of therapeutic targets. Different forms of pathological pain alter nociceptive processing in the superficial dorsal horn (SDH) of the spinal cord through distinct mechanisms, but these differences are not well understood.1-4 The purpose of this project was to develop and and apply an ex-vivo SDH Ca2+ imaging pipeline to screen different forms of pathological pain.
Methods
We employed several models of pathological pain: acute inflammatory (Capsaicin), protracted inflammatory (Complete Freud’s Adjuvant, CFA), neuropathic (Spared Nerve Injury, SNI), and osteoarthritic (ACL transection, OA). All models exhibited peripheral mechanical hypersensitivity after injury. We captured network wide SDH dynamics of spontaneous and evoked cellular activity, under various pain conditions, using epifluorescent Ca2+ imaging in an ex-vivo
setup.5 To confirm this approach could elucidate alterations in cellular Ca2+ responses, we applied blockers of GABAergic and glycinergic receptor mediated inhibition (bicuculline and strychnine), a model of disinhibition.
Results
We observed that SDH cells exhibited a higher amplitude of Ca2+ response to glutamate in ipsilateral compared to contralateral controls. When glutamate was applied to stimulate neuronal activity, we found that the SDH neurons from Capsaicin, CFA, and SNI models exhibited a higher amplitude of Ca2+ response compared to controls, while the OA model did not elicit a difference in response. Unexpectedly, the number of spontaneously active neurons, in the absence of glutamate, was significantly decreased in the OA, Capsaicin, and CFA models.
Conclusions
Collectively, our findings provide further insight into the diverse manifestations of inflammatory, neuropathic, and osteoarthritic pain across different time scales in the spinal cord.
References
1 Kuner R. (2010). Central mechanisms of pathological pain. Nature medicine, 16(11), 1258–1266. https://doi.org/10.1038/nm.2231
2 Baron, R., Binder, A., & Wasner, G. (2010). Neuropathic pain: diagnosis, pathophysiological mechanisms, and treatment. The Lancet. Neurology, 9(8), 807–819. https://doi.org/10.1016/S1474-4422(10)70143-5
3 Costigan, M., & Woolf, C. J. (2000). Pain: molecular mechanisms. The journal of pain, 1(3 Suppl), 35–44. https://doi.org/10.1054/jpai.2000.9818
4 Luo, C., Kuner, T., & Kuner, R. (2014). Synaptic plasticity in pathological pain. Trends in neurosciences, 37(6), 343–355. https://doi.org/10.1016/j.tins.2014.04.002
5 Doolen, S., Blake, C. B., Smith, B. N., & Taylor, B. K. (2012). Peripheral nerve injury increases glutamate-evoked calcium mobilization in adult spinal cord neurons. Molecular pain, 8, 56. https://doi.org/10.1186/1744-8069-8-56
Presenting Author
Samuel Fung
Poster Authors
Samuel Fung
BSc(Hons)
University of Toronto
Lead Author
Erika Harding
PhD
Hotchkiss Brain Institute, University of Calgary
Lead Author
Jo Anne Stratton
PhD
Montreal Neurological Hospital and Institute, Department of Neurology, McGill University
Lead Author
Stephanie Norlock
MSc
Department of Neuroscience, Carleton University
Lead Author
Jenny Cheung
BSc
Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toront
Lead Author
Hantao Zhang
BSc
Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toront
Lead Author
Jeff Biernaskie
PhD
Hotchkiss Brain Institute, University of Calgary
Lead Author
Michael E Hildebrand
PhD
Department of Neuroscience, Carleton University
Lead Author
Robert P. Bonin
Lead Author
Topics
- Mechanisms: Biological-Systems (Physiology/Anatomy)