Autonomic Dysreflexia Persists Following Acute Rehabilitation in Rats with Incomplete Contusive Spinal Cord Injury
Bibliographic record
Abstract
Introduction Disruption of autonomic pathways following spinal cord injury (SCI) leads to altered cardiovascular (CV) function and homeostasis. The level and completeness of injury have great ramifications on the clinical presentation of CV pathology. Severe cervical and high thoracic lesions disrupt supraspinal control of sympathetic preganglionic neurons of the heart and upper body vasculature, leading to a state in which episodic hypertensive crises known as autonomic dysreflexia (AD) can develop. Rodent studies utilizing complete transection of the upper thoracic cord have shown that appropriately‐timed rehabilitation has the ability to reduce the severity of AD and normalize cardiac function. To date, no study has examined the impact of acute rehabilitation on CV function in a more clinically relevant contusive SCI model. Our objective was to evaluate the effects of either passive hind limb cycling (PHLC) or active swimming therapy on the development and severity of AD following severe T2 contusion. Methods Male Wistar rats with severe T2 contusions (400 kDyn, 5 second dwell, Infinite Horizons Impactor), were randomly divided into three groups: Control (T2‐CON, n=7), PHLC (T2‐ PHLC, n=5), or Swim rehabilitation (T2‐SWIM, n=6). A fourth group received T10 severe contusions and served as injured controls with intact cardiac sympathetic preganglionic pathways (T10‐CON, n=6). Rehabilitation therapy began 7 days post injury, and lasted for three weeks (30 minutes per day, 5 days per week). Five weeks post injury, rats were implanted with telemetric blood pressure devices (Millar, TRM54P) and pressor responses (i.e. AD) induced by colorectal distension (CRD) were evaluated. Results Resting hemodynamics did not differ between T2‐ PHLC, T2‐SWIM, and T2‐CON groups. Animals that received T10 injuries developed resting tachycardia (all groups p < .05). Pressor responses to CRD varied considerably across animals, but were significantly greater in T2 contused animals than in T10‐CON (all groups p < .05), and neither rehabilitation approach was able to attenuate the hypertensive crisis in response to CRD. However, if each group was subdivided based on BBB score, animals with low BBB scores (≤ 6) in the PHLC group were not statistically different from T10‐CON (p = .055). Conversely, both T2‐CON and T2‐SWIM animals with low BBB scores exhibited greater pressor responses during CRD (both groups p < .05). Conclusions Using a clinically relevant contusive model of SCI, we show that neither PHLC nor active swimming rehabilitation has the ability to favorably impact CV responses to CRD in incompletely injured T2 rats. However, if the most severely injured animals are assessed separately (BBB scores ≤ 6), PHLC appears to improve CV homeostasis and reduce the severity of pressor responses during CRD. This data suggests a relationship between locomotor recovery and CV function independent of applied PHLC or swim exercise that may depend more on improvements in hind limb activity and/or tissue sparing at the injury epicenter. Support or Funding Information iCORD VISIT Scholarship, CIHR, CNF, Kentucky Spinal Cord and Head Injury Trust (P30 RR031159), NIH (R56 NS052292), and Friends for Micheal
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".