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

IF 3.5 2区医学 Q1 ANESTHESIOLOGY

European Journal of Pain Pub Date : 2024-08-08 DOI:10.1002/ejp.4701

Ken Steffen Frahm, Ole Kæseler Andersen, Lars Arendt-Nielsen, Sabata Gervasio, Carsten Dahl Mørch

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Abstract

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.

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局部辣椒素可调节两点辨别阈值--调节取决于刺激方式和强度。

背景：空间敏锐度涉及对感觉输入进行定位和分辨的能力，通常使用两点分辨阈值（2PDT）进行测试。疼痛系统的敏感性会影响空间敏锐度，但目前还不清楚不同测试模式的 2PDT 会受到怎样的影响。我们的目的是研究不同强度的机械刺激和热刺激的 2PDT 是否会受到局部辣椒素致敏的影响。方法：30 名健康受试者被分为辣椒素组和安慰剂组。方法：30 名健康受试者被分为辣椒素组和安慰剂组，使用两种不同的方式，即无害强度和有害强度的机械刺激和热刺激（激光），对 2PDT 进行测试。2PDT 在基线时测定，48 小时后再次评估。在后续环节中，受试者在测试区域贴上辣椒素贴片（8%）或安慰剂贴片 30 分钟，然后重新测试 2PDT ：结果：2PDT 与刺激方式和强度有很大关系。无害机械刺激的 2PDT 最低（40.0 毫米，95% CI 38.1-41.9 毫米），无害热刺激的 2PDT 最高（81.7 毫米，95% CI 73.9-89.5 毫米）。外用辣椒素通常会增加 2PDT 值，但这只对无害的机械刺激有显著影响。使用辣椒素后，对刺激强度的感知增加，并且有害刺激的感知强度普遍高于无害刺激（方差分析，P 结论）：本研究表明，辣椒素引起的痛觉过敏增加了 2PDT 。使用无害机械刺激进行的 2PDT 测试结果变化较小，表明该测试最适合检测空间敏锐度的这一方面：本研究调查了局部辣椒素如何调节两点辨别阈值（2PDT）。在使用辣椒素前后，对两种不同模式（热和机械）和两种不同强度（无害和有害）的 2PDT 进行了评估。结果表明，在服用辣椒素后，2PDT 普遍受损，但这只对机械性无害刺激有显著影响。此外，与其他组合相比，机械性无害刺激对 2PDT 的评估变异性较低。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

European Journal of Pain 医学-临床神经学

CiteScore

7.50

自引率

5.60%

发文量

163

审稿时长

4-8 weeks

期刊介绍： European Journal of Pain (EJP) publishes clinical and basic science research papers relevant to all aspects of pain and its management, including specialties such as anaesthesia, dentistry, neurology and neurosurgery, orthopaedics, palliative care, pharmacology, physiology, psychiatry, psychology and rehabilitation; socio-economic aspects of pain are also covered. Regular sections in the journal are as follows: • Editorials and Commentaries • Position Papers and Guidelines • Reviews • Original Articles • Letters • Bookshelf The journal particularly welcomes clinical trials, which are published on an occasional basis. Research articles are published under the following subject headings: • Neurobiology • Neurology • Experimental Pharmacology • Clinical Pharmacology • Psychology • Behavioural Therapy • Epidemiology • Cancer Pain • Acute Pain • Clinical Trials.