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