Long-duration, low-concentration topical capsaicin diminishes central sensitization
Bibliographic record
Abstract
The development of chronic pain is typically predicated by neuroplastic changes within the spinal cord in response to persistent noxious stimuli, termed central sensitization. Sensitization increases the sensitivity to stimuli of neurons directly in contact with the initial noxious stimulus, termed primary hyperalgesia, as well as those in the adjacent regions, termed secondary hyperalgesia. TRPV1 receptors, found throughout the spinal cord and periphery, are key contributors to the development t of sensitization. Capsaicin, the active ingredient in chili peppers, is a known agonist of TRPV1 receptors and, due to the unique ability of these receptors to become defunctionalized with intense or prolonged capsaicin exposure, is a common ingredient in pain relieving ointments. Defunctionalization, via capsaicin, eliminates the typical primary sensitization and has been demonstrated through the application of high dosage (>5%) capsaicin treatments. The purpose of this study was to analyze the effects of defunctionalizing capsaicin-sensitive nociceptors, using a prolonged low concentration (<1%) capsaicin treatment, on peripheral and central pain development. Following the application period, a battery of quantitative sensory assessments were performed. Following our intervention, heat and cold pain perceptions during heat and cold evoked potentials were significantly lower in the capsaicin region compared to the control region. Analysis of the neurophysiological outcomes from the evoked potentials, revealed that contact heat, but not cold, evoked potential amplitudes at the capsaicin treatment region were significantly decreased. Heat pain and warm detection thresholds were significantly increased in the capsaicin treated region whereas cold pain or cold detection thresholds did not change. Mechanical pain sensitivity following the heat sensitization protocol, increased in the control but not the capsaicin region. These findings indicate that prolonged, low-concentration, capsaicin application successfully defunctionalized TRPV1 receptors and diminished secondary hyperalgesia development in the capsaicin treated region. These findings suggest that the use of low concentration capsaicin may be beneficial in preventing central sensitization in conditions such as chronic pain.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".