Psychophysical Studies of Itch

瘙痒是一种常见的临床问题，有时甚至会使人丧失能力。有几条证据表明 灵长类动物的脊髓丘脑束(STT)神经元携带瘙痒信息。我们最近在寻找 痛觉(瘙痒编码)STT灵长类神经元投射到丘脑腹侧后外侧核(VPL) 丘脑表明，这些只解释了由瘙痒刺激引起的伤害性特征。但更远的地方 需要研究来完成我们对这些神经元的调查。这个项目的一个主要目标是检查 构成STT的其他几个主要成分的神经元对瘙痒刺激的反应 灵长类动物。我们将使用机械、热和化学刺激，包括组胺和母牛饲料 针叶-后者被认为能引起组胺非依赖性瘙痒-用于心理物理研究 项目1中的瘙痒。我们将确定STT神经元投射到VPL或腹侧后下或 用微逆刺激方法研究丘脑后核团。我们将确定以下方面的回应 这些神经元对瘙痒刺激的反应在统计上与对心理物理功能的反应相匹配 描述由这些和其他刺激产生的瘙痒或疼痛的潜伏期、强度和持续时间。这将是 使我们能够确定被检查的神经元是否对瘙痒或 伤害性刺激。瘙痒化学物质会产生大面积的皮肤瘙痒(同种异体膝曲)。我们将决定 STT神经元反应的改变是否可以解释皮肤瘙痒的发生。我们还将 确定潜在重要的一类非常缓慢传导的STT轴突 猫的症状也存在于猴子身上，如果它们对瘙痒和伤害性刺激有反应。在决赛中 一系列的实验，我们将检查皮肤手法的效果，已知可以增加或 减少STT的瘙痒反应(包括温暖、冷却和抓挠) 神经元。这些研究应该为深入了解脊髓和丘脑的机制提供帮助。 潜在的瘙痒及其抑制，因此，可能导致改善慢性瘙痒的治疗。

Itch is a common and sometimes disabling clinical problem. Several lines of evidence indicate that spinothalamic tract (STT) neurons in primates carry pruriceptive information. Our recent search for pruriceptive (itch coding) STT primate neurons projecting to the ventral posterior lateral nucleus (VPL) of thalamus suggest that these account only for the nociceptive qualities evoked by pruritic stimuli. But further studies are needed to complete our survey of these neurons. A major goal of this project is to examine the responses to pruritic stimuli of neurons that form several of the other major components of the STT in primates. We will use mechanical, thermal and chemical pmritic stimuli including histamine and cowhage spicules -the latter believed to evoke a histamine-independent itch - that are used in psychophysical studies of itch in Project 1. We will identify STT neurons that project to either VPL or to the ventral posterior inferior or posterior nuclei of thalamus using micro-antidromic stimulation methods. We will determine the responses of these neurons to pruritic stimuli and statistically match the responses to psychophysical functions that describe the latency, intensity and duration of itch or pain produced by these and other stimuli. This will allow us to determine whether an examined neuron responds specifically or selectively to pruritic or nociceptive stimuli. Pruritic chemicals produce large areas of itchy skin (alloknesis). We will determine whether changes in the responses of STT neurons can account for occurrence of itchy skin. We will also determine whether the potentially important class of very slowly conducting STT axons that have been described in cats also exist in monkeys and if they respond to pruritic and nociceptive stimuli. In the final series of experiments, we will examine the effects of cutaneous manipulations that are known to increase or decrease the sensation of itch (including warming, cooling, and scratching) on pruritic responses of STT neurons. These studies should provide insight into to the mechanisms in both the spinal cord and thalamus underlying itch and its inhibition, and, thereby, potentially lead to improved treatments of chronic itch.