Cliff M A, Green B G
Agriculture & Agri-Food Canada, Research Centre, Summerland, Canada.
Physiol Behav. 1996 Mar;59(3):487-94. doi: 10.1016/0031-9384(95)02089-6.
It was reported in a recent study that, like capsaicin, menthol is capable of producing a desensitization to sensory irritation in the oral cavity. Whereas capsaicin is known to be able to cross-desensitize with other chemical irritants, no such information exists for menthol. To address this question, the first experiment was designed to reveal whether cross-desensitization would occur between menthol and capsaicin. After a pretest on the tongue tip in which subjects rated the intensity of irritation and cold produced by 3.5 ppm capsaicin or 0.3% l-menthol, five samples of the same stimuli were sipped and swished at 1-min intervals for 5 min. Fifteen minutes later subjects were tested on the tongue tip with either capsaicin or menthol. The results 1) confirmed self-desensitization for both chemicals, 2) demonstrated cross-desensitization of menthol by capsaicin, and 3) revealed cross-sensitization of capsaicin by menthol. This series of outcomes suggests that menthol produces much of its sensory irritation via capsaicin-sensitive pathways, but that it excites and/or desensitizes those pathways via different mechanisms than does capsaicin. Analysis of the individual data revealed large differences in sensitization, and desensitization that were significantly correlated across chemicals, which suggests the possibility that the perceptual response to repeated exposures to irritants may be idiosyncratic. Contrary to earlier findings, the first experiment also revealed apparent self- and cross-desensitization of the menthol sensation of coolness. The latter outcome was investigated in a second experiment in which the effect of capsaicin desensitization on the perception of physical as well as chemical (menthol) cooling was measured when the stimuli were presented as oral rinses. No desensitization was found for either form of stimulation, which implied the apparent desensitization of coolness in Experiment I may have been due to the difficulty of discriminating sensations of cold from sensations of chemical irritation. The overall findings are discussed in terms of the complex sensory and perceptual interactions that take place within the chemesthetic modality.
最近一项研究报道，与辣椒素一样，薄荷醇能够使口腔对感觉刺激产生脱敏作用。虽然已知辣椒素能够与其他化学刺激物产生交叉脱敏，但关于薄荷醇却没有此类信息。为解决这个问题，第一个实验旨在揭示薄荷醇和辣椒素之间是否会发生交叉脱敏。在对舌尖进行预测试，让受试者对3.5 ppm辣椒素或0.3% l - 薄荷醇产生的刺激强度和冷感进行评分后，每隔1分钟啜饮并漱口5次相同刺激物的样品，共持续5分钟。15分钟后，用辣椒素或薄荷醇对受试者的舌尖进行测试。结果表明：1）证实了两种化学物质的自身脱敏作用；2）证明了辣椒素对薄荷醇的交叉脱敏作用；3）揭示了薄荷醇对辣椒素的交叉致敏作用。这一系列结果表明，薄荷醇通过辣椒素敏感途径产生其大部分感觉刺激，但它通过与辣椒素不同的机制来激发和/或使这些途径脱敏。对个体数据的分析揭示了致敏和脱敏方面的巨大差异，这些差异在不同化学物质之间具有显著相关性，这表明对反复接触刺激物的感知反应可能具有个体特异性。与早期研究结果相反，第一个实验还揭示了薄荷醇凉爽感明显的自身和交叉脱敏现象。在第二个实验中对后一结果进行了研究，在该实验中，当刺激物以口腔冲洗液形式呈现时，测量辣椒素脱敏对物理冷却以及化学（薄荷醇）冷却感知的影响。对于任何一种刺激形式均未发现脱敏现象，这意味着实验一中凉爽感的明显脱敏可能是由于难以区分冷感和化学刺激感所致。本文根据化学感觉模态内发生的复杂感觉和感知相互作用对总体研究结果进行了讨论。
