Topical capsaicin modulates the two-point discrimination threshold-Modulation depends on stimulation modality and intensity.

Autor: Frahm KS; Integrative Neuroscience Group, CNAP-Center for Neuroplasticity and Pain, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark., Andersen OK; Integrative Neuroscience Group, CNAP-Center for Neuroplasticity and Pain, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark., Arendt-Nielsen L; Translational Pain Biomarkers, CNAP-Center for Neuroplasticity and Pain, SMI®, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.; Department of Gastroenterology & Hepatology, Mech-Sense, Department of Clinical Medicine, Aalborg University Hospital, Aalborg, Denmark.; Steno Diabetes Center North Denmark, Aalborg University Hospital, Aalborg, Denmark., Gervasio S; Neural Engineering and Neurophysiology Group, SMI®, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark., Mørch CD; Integrative Neuroscience Group, CNAP-Center for Neuroplasticity and Pain, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
Jazyk: angličtina
Zdroj: European journal of pain (London, England) [Eur J Pain] 2024 Nov; Vol. 28 (10), pp. 1855-1865. Date of Electronic Publication: 2024 Aug 08.
DOI: 10.1002/ejp.4701
Abstrakt: Background: Spatial acuity concerns the ability to localize and discriminate sensory input and is often tested using the two-point discrimination threshold (2PDT). Sensitization of the pain system can affect the spatial acuity, but it is unclear how 2PDTs of different testing modalities are affected. The aim was to investigate if the 2PDTs for mechanical and heat stimulation at different intensities were modulated by topical capsaicin sensitization.
Methods: 30 healthy subjects were divided into either a capsaicin or a placebo group. The 2PDT was tested using two different modalities, mechanical and thermal (laser) delivered at innocuous and noxious intensities. The 2PDT were determined at baseline and re-assessed 48 h later. In the follow-up session, the subjects either had a capsaicin patch (8%) or placebo patch placed in the testing area for 30 min before re-testing the 2PDT.
Results: The 2PDT was highly dependent on stimulation modality and intensity. The lowest 2PDT was found for innocuous mechanical stimuli (40.0 mm, 95% CI 38.1-41.9 mm), and the highest 2PDT was found for innocuous thermal stimuli (81.7 mm, 95% CI 73.9-89.5 mm). Topical capsaicin generally increased the 2PDT, but this was only significant for innocuous mechanical stimuli. The perceived intensity of the stimuli was increased following capsaicin and was generally higher for noxious stimuli than for innocuous stimuli (ANOVA, p < 0.001).
Conclusions: This study showed that capsaicin provoked pain sensitization increased the 2PDT. The 2PDT tested using innocuous mechanical stimuli showed less variable results indicating that this test is most suitable to detect this aspect of spatial acuity.
Significance Statement: This study investigated how the two-point discrimination threshold (2PDT) can be modulated by topical capsaicin. The 2PDT was assessed for two different modalities (thermal and mechanical) and for two different intensities (innocuous and noxious) before and after capsaicin. The results showed that the 2PDT was generally impaired following capsaicin, but this was only significant for mechanical innocuous stimuli. Furthermore, it was shown that mechanical innocuous stimuli assessed the 2PDT with lower variability than other combinations.
(© 2024 The Author(s). European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation ‐ EFIC ®.)
Databáze: MEDLINE
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