Altered transcription of glutamatergic and glycinergic receptors in spinal cord dorsal horn following spinal cord transection is minimally affected by passive exercise of the hindlimbs

Abstract

Gene expression is altered following a spinal transection (STx) in both motor and sensory systems. Exercise has been shown to influence gene expression in both systems post-STx. Gene expression alterations have also been shown in the dorsal root ganglia and nociceptive laminae of the spinal cord following either an incomplete spinal cord injury (SCI) or a contusive SCI. However, the effect of STx and exercise on gene expression in spinal cord laminae I-III has not fully been examined. Therefore, the purpose of this study was to determine whether gene expression in laminae I-III is altered following STx and determine whether superimposed passive exercise of the hindlimbs would influence gene expression post-STx in laminae I-III. Laser capture microdissection was used to selectively harvest laminae I-III of lumbar spinal cord sections, and quantitative RT-PCR was used to examine relative expression of 23 selected genes in samples collected from control, STx and STx plus exercise rats. We demonstrate that post-STx, gene expression for metabotropic glutamate receptors 1, 5 and 8 were up-regulated, whereas ionotropic glutamatergic receptor (Glur2) and glycinergic subunit GLRA1 expression was down-regulated. Daily exercise attenuated the down-regulation of Glur2 gene expression in laminae I-III. Our results demonstrate that in a STx model, gene expression is altered in laminae I-III and that although passive exercise influences gene expression in both the motor and sensory systems, it had a minimal effect on gene expression in laminae I-III post-STx.

Three-Week Treadmill Exercise Enhances Persistent Inward Currents, Facilitates Dendritic Plasticity, and Upregulates the Excitability of Dorsal Raphe Serotonin Neurons in ePet-EYFP Mice

“…Neurons are remarkable in their capacity to respond and adapt to environmental changes through synaptic plasticity and channel mechanisms. It has been shown in numerous studies that exercise, as one of the environmental changes, improves the excitability of neurons through hyperpolarization of the voltage threshold, increase in action potential (AP) discharge rate, and reduction in rheobase (Beaumont and Gardiner, 2002 ; Gardiner, 2006 ; Gardiner et al, 2006 ; Krutki et al, 2015 ; Chopek et al, 2018 ; MacDonell and Gardiner, 2018 ). Conversely, in the case of restricted activity such as spinal cord transection or suspension of the hindlimbs, changes in the membrane properties are opposite to those induced in the increased activity (Cormery et al, 2005 ).…”

Mechanisms of spinal cord stimulation for the treatment of pain: Still in the dark after 50 years

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