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Activity-based Training on a Treadmill with Spinal Cord Injured Wistar Rats

Spinal cord injury (SCI) results in lasting deficits that include both mobility and a multitude of autonomic-related dysfunctions. Locomotor training (LT) ...

University of Louisville

Spinal cord injury (SCI) causes dramatic changes in the quality of life, including coping with bladder dysfunction which requires repeated daily and nightly catheterizations. Our laboratory has recently demonstrated in a rat SCI model that repetitive sensory information generated through task-specific stepping and/or loading can improve nonlocomotor functions, including bladder function (Ward PJ, Herrity AN, Smith RR, Willhite A, Harrison BJ, Petruska JC, Harkema SJ, Hubscher CH. J Neurotrauma 31: 819-833, 2014). To target potential underlying mechanisms, the current study included a forelimb-only exercise group to ascertain whether improvements may be attributed to general activity effects that impact target organ-neural interactions or to plasticity of the lumbosacral circuitry that receives convergent somatovisceral inputs. Male Wistar rats received a T9 contusion injury and were randomly assigned to three groups 2 wk postinjury: quadrupedal locomotion, forelimb exercise, or a nontrained group. Throughout the study (including preinjury), all animals were placed in metabolic cages once a week for 24 h to monitor water intake and urine output. Following the 10-wk period of daily 1-h treadmill training, awake cystometry data were collected and bladder and kidney tissue harvested for analysis. Metabolic cage frequency-volume measurements of voiding and cystometry reveal an impact of exercise training on multiple SCI-induced impairments related to various aspects of urinary tract function. Improvements in both the quadrupedal and forelimb-trained groups implicate underlying mechanisms beyond repetitive sensory information from the hindlimbs driving spinal network excitability of the lumbosacral urogenital neural circuitry. Furthermore, the impact of exercise training on the upper urinary tract (kidney) underscores the health benefit of activity-based training on the entire urinary system within the SCI population.

Effects of exercise training on urinary tract function after spinal cord injury.

Urinary dysfunction is a common complaint following spinal cord injury (SCI) and is a leading issue for individuals with SCI that impacts their quality of life. One urinary complication that has received little attention is SCI-induced polyuria, even though individuals with SCI will significantly restrict their fluid intake to decrease urine production, leading to sequelae of medical complications. Understanding the mechanisms instigating the development of polyuria will allow us to target interventions that may alleviate polyuria symptoms, leading to significant improvements in the quality of life and urinary health of individuals with SCI. In a rat SCI contusion model, an increase in the amount of urine excreted over a 24-h period ( P ≤ 0.001) was found at 2 wk postinjury. The urine excreted was more dilute with decreased urinary creatinine and specific gravity ( P ≤ 0.001). Several factors important in fluid balance regulation, vasopressin (AVP), natriuretic peptides, and corticosterone (CORT), also changed significantly postinjury. AVP levels decreased ( P = 0.042), whereas atrial natriuretic peptide (ANP) and CORT increased ( P = 0.005 and P = 0.031, respectively) at 2 wk postinjury. There was also a positive correlation between the increase in ANP and urine volume postinjury ( P = 0.033). The changes in AVP, ANP, and CORT are conducive to producing polyuria, and the timing of these changes coincides with the development of SCI-induced polyuria. This study identifies several therapeutic targets that could be used to ameliorate polyuria symptoms and improve quality of life in individuals with SCI.

Altered vasopressin and natriuretic peptide levels in a rat model of spinal cord injury: implications for the development of polyuria.

Locomotor training (LT) as a therapeutic intervention following spinal cord injury (SCI) is an effective rehabilitation strategy for improving motor outcomes, but its impact on non-locomotor functions is unknown. Given recent results of our labs' pre-clinical animal SCI LT studies and existing overlap of lumbosacral spinal circuitries controlling pelvic-visceral and locomotor functions, we addressed whether LT can improve bladder, bowel and sexual function in humans at chronic SCI time-points (> two years post-injury).

Lynnette R. Montgomery

Department of Anatomical Sciences and Neurobiology

University of Louisville

Activity-based Training on a Treadmill with Spinal Cord Injured Wistar Rats

Lynnette R. Montgomery

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Anatomical Sciences and Neurobiology

University of Louisville

Activity-based Training on a Treadmill with Spinal Cord Injured Wistar Rats

Department of Anatomical Sciences and Neurobiology