Topical menthol--a human model for cold pain by activation and sensitization of C nociceptors
Bibliographic record
Abstract
Although cold hyperalgesia is a frequent symptom in patients with neuropathic pain, it is poorly understood. We investigated the mechanisms of cold pain by studying the effect of menthol on pain, temperature perception, touch sensation and skin perfusion. In 10 subjects, 40% l-menthol, and ethanol, serving as control, were topically applied to the forearm in a double-blinded two-way crossover study. Menthol induced significant pain and cold sensations, punctate and cold hyperalgesia and an increase in cutaneous perfusion. Other mechano-sensory and thermal tests were unchanged (touch, cold and warm detection thresholds, heat pain threshold; no dynamic and static hyperalgesia, no wind-up). To investigate the underlying mechanisms, the effects of menthol versus ethanol on the dorsum of the hand were tested during A fibre conduction blockade of the superficial radial nerve in another 10 subjects. The block itself led to hypoaesthesia for mechanical stimuli and anaesthesia for cold perception, but induced an increase in cold-mediated pain. This was due to lack of inhibition of C nociceptors normally exerted by concomitant activation of A fibres. Under these conditions, menthol-induced cold sensation and punctate hyperalgesia were abolished. However, menthol induced spontaneous pain with a trend to higher values than without block. Furthermore, the hyperalgesia to cold stimuli, that was already present during A fibre block, was further increased significantly by menthol. We suggested that menthol acts to sensitize cold-sensitive peripheral vasoactive C nociceptors and activates cold-specific A delta fibres. Punctate hyperalgesia is due to central sensitization based on the ongoing activity in the sensitized cold-sensitive peripheral C nociceptors. In conclusion, topical menthol is a human model for cold pain by exposing for the first time the mechanism of sensitized peripheral cold C nociceptors that may also be involved in neuropathic pain.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".