Time-course of analgesic effects of botulinum neurotoxin type A (BoNTA) on human experimental model of pain induced by injection of glutamate into temporalis muscle
Bibliographic record
Abstract
Abstract Background/aims Analgesic effects of BoNTA develop within few hours in animal studies and within days in human studies. We have previously shown that BoNTA can block glutamate-induced mechanical sensitization and neurogenic vasodilation in rat temporalis muscle within 3 h. The present translational study was designed to explore the time-course of analgesic effects of BoNTA on pain, sensitization and vasomotor responses in a glutamateevoked human pain model. Methods BoNTA (5U) and saline were injected (30 min interval) into the left and right temporalis muscles of 12 healthy males (24.2° 2 years). Pressure pain threshold (PPT), skin temperature (thermo camera) and tissue perfusion (laser Doppler flowmetry) were measured every hour for 3 h. Afterwards, subjects received an intramuscular injection of glutamate (1M– 0.2 mL) into the left and right temporalis muscles. Pain intensity (VAS) was recorded for 10 min after injection and pain distribution was then mapped. PPT was measured at 15 and 30 min following the glutamate injections, while skin temperature and tissue perfusion were recorded at 5, 15 and 30 min. Results This preliminary data showed that BoNTA significantly reduced glutamate-evoked peak pain intensity compared with saline ( P = 0.042). Expansion of pain area was also smaller in the muscles pretreated with BoNTA ( P = 0.045). Glutamate-induced vasomotor reactions (elevated skin temperature and tissue perfusion) showed a tendency to decline in BoNTA-pretreated muscles. A similar pattern was seen in terms ofmuscle sensitivity with higher PPT values in BoNTA-pretreated muscles. Conclusions BoNTA induced a direct analgesic effect withi 3 h of its injection into the temporalis muscle. This phenomenon, at least in part, might be through BoNTA actions on nociceptors. Present data also indicated that BoNTA attenuated glutamateinduced muscle sensitization and vasomotor reactions. This finding may suggest additional effects of BoNTA on the pattern of release of substances which are involved in pain pathways.
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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 | 0.000 |
| 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".