Psychophysical Studies of Itch

瘙痒(瘙痒)是一个主要的临床问题，也是最令人不安的皮肤和许多 系统性疾病。在正常皮肤中，瘙痒可以由各种瞬时刺激引起，而不会改变 皮肤敏感度。相反，在病理条件下，例如由皮炎、昆虫引起的 叮咬或试验性地使用组胺等瘙痒化学物质，加剧瘙痒状态 (“皮肤瘙痒”)在受影响的皮肤内部和周围发展。在发痒的皮肤上，通常会引起瘙痒刺激 强烈的瘙痒(多膝)和无害的刺激可以唤起或增强持续的瘙痒或唤起 疼痛增强(分别为同种异体膝曲和痛觉过敏)。关于瘙痒的心理物理学的研究很少。 或者是躯体传入通路来调节瘙痒。同样，很少有心理物理学的研究 对瘙痒的抑制或对调节抑制的神经机制的研究。我们建议 对瘙痒的心理物理研究，以及疼痛和其他非瘙痒皮肤刺激对瘙痒的调节 正常皮肤和化学诱导的瘙痒皮肤。对于正常和瘙痒的皮肤，我们都会使用单一的 用形容词标记量表比较痛痒感觉的大小和时间进程 机械、热和化学刺激。瘙痒和疼痛的大小和时间进程的差异 在项目2和项目3中，可以使用由每个刺激引起的感觉来区分瘙痒和疼痛编码 感觉神经元。我们将测试非瘙痒条件刺激(CS)在调制皮肤瘙痒中的作用。 皮肤正常，皮肤瘙痒，皮肤瘙痒的发展和持续。我们将检验这一假设 有两个瘙痒感觉系统，一个负责调节瘙痒，另一个是皮肤瘙痒，每个系统都在 两个不同伤害性感受系统的抑制控制--一个在暴露于CS的区域内工作 以及调节疼痛或原发性痛觉过敏，另一种作用于更广泛的区域，并调节继发性疼痛 痛觉过敏和/或痛觉过敏。这些研究的结果不仅将增加我们对瘙痒的理解 皮肤发痒。它们还将提供关于抑制瘙痒的内源性机制的新信息，以及 可能是开发止痒药物的合适靶点。

Itching (pruritus) is a major clinical problem and one of the most disturbing symptoms of cutaneous and many systemic diseases. In normal skin, itch can be evoked by a variety of transient stimuli with no changes in cutaneous sensitivity. In contrast, under pathological conditions brought on, for example, by dermatitis, insect bites or experimentally by the application of a pruritic chemical such as histamine, a heightened pruritic state ("itchy skin") develops within and surrounding the affected skin. In itchy skin, normally pruritic stimuli elicit an enhanced itch (hyperknesis) and innocuous stimuli can evoke or enhance an ongoing itch or evoke an enhanced pain (alloknesis and hyperalgesia, respectively). There are few studies of the psychophysics of itch or of the somatic afferent pathways mediating itch. Similarly, there have been few psychophysical studies of the inhibition of itch or studies of the neural mechanisms mediating the inhibition. We propose psychophysical studies of itch, and its modulation by painful and other non-pruritic cutaneous stimuli, in normal skin and in chemically induced itchy skin. For both normal and itchy skin we will use a single adjective-labeled scale to compare the magnitude and time course of itch and pain sensations evoked by mechanical, heat and chemical stimuli. Differences in the magnitude and time course of itch and pain sensations evoked by each stimulus can be used in projects 2 and 3 to distinguish itch- from pain-coding sensory neurons. We will test the effects of non-pruritc conditioning stimuli (CS) in modulating itch in normal skin, itch in itchy skin and the development and persistence of itchy skin. We will test the hypothesis that there are two pruriceptive systems, one mediating itch, the other itchy skin and that each of these is under the inhibitory control of two different nociceptive systems - one operating within the area exposed to the CS and mediating pain or primary hyperalgesia, the other operating over a wider area and mediating secondary hyperalgesia and/or allodynia. The outcome of these studies will not only increase our understanding of itch and itchy skin. They will also provide novel information on endogenous mechanisms that inhibit itch and that may be appropriate targets for the development of drugs to control itching.