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Preclinical pilot study. To test the hypothesis that spinal opioidergic circuitry contributes to muscle stretch-induced locomotor deficits. Kentucky Spinal Cord Injury Research Center, Louisville, KY, USA. A pilot study with eight female Sprague-Dawley rats that received 25 g-cm T10 contusion injuries and recovered for 5 weeks. Rats were divided into two groups with one group receiving subcutaneous injections of naltrexone dissolved in saline (15 mg/kg) or an equal volume of saline. Each group received a daily 24-minute stretching protocol during weeks 6, 8, and 11 post-injury. Locomotor function was assessed throughout using the BBB Open Field Locomotor Scale. Consistent with previous findings, stretching reduced locomotor function in both naltrexone and saline groups. However, the loss of locomotor function appeared earlier in the naltrexone group. Animals in both groups had a similar rate of recovery following the termination of stretching. Interestingly, the administration of naltrexone did not influence acute thermal cutaneous nociceptive responses as measured by a tail-flick assay but caused a significant increase in spasticity following stretch. The results of this study suggest that the endogenous opioid system plays a role in modulating the negative impact of muscle stretch on spinal cord motor circuitry that is vulnerable due to loss of descending input. The observed actions of the broad-spectrum opioid antagonist naltrexone imply that pharmaceuticals targeting the endogenous opioid system post-SCI may have unintended consequences.

Spinal cord injury (SCI) is a devastating clinical condition resulting in significant disabilities. Apart from local injury within the spinal cord, SCI patients develop a myriad of complications including multi-organ dysfunction. Some of the dysfunctions may be directly or indirectly related to the sensory neurons of the dorsal root ganglia (DRG), which signal to both the spinal cord and the peripheral organs. After SCI, some classes of DRG neurons exhibit sensitization and undergo axonal sprouting both peripherally and centrally. Such physiological and anatomical re-organization after SCI contributes to both adaptive and maladaptive plasticity processes, which may be modulated by activity and exercise. In this study, we collected comprehensive gene expression data in whole DRG below the levels of the injury to compare the effects of SCI with and without two different forms of exercise in rats., Design Type(s)gene expression analysis objective • stimulus or stress design • transcription profiling designMeasurement Type(s)gene expressionTechnology Type(s)RNA sequencingFactor Type(s)Spinal Cord Injury • Exercise • biological replicateSample Characteristic(s)Rattus norvegicus • dorsal root ganglion Machine-accessible metadata file describing the reported data (ISA-Tab format)