Central Neural Mechanisms of Itch

与几种情况相关的瘙痒可以用抗组胺药物有效地治疗。然而，引起的瘙痒 受很多条件影响，包括比较常见的皮肤病和全身性疾病，都不能。 由于目前没有有效的治疗方法，这些后一种类型的瘙痒构成了相当大的临床问题。 可用。在之前的资助期间，我们的团队已经表明，不同的灵长类种群 脊髓丘脑束(STT)神经元对皮内注射组胺产生瘙痒刺激的反应 以及Cowhage，一种临床上重要的非组胺能瘙痒模型。我们的研究结果表明， 中枢神经系统内的通路携带有关组胺能和非组胺能形式的瘙痒的信息。在……里面 实验在特定目标1下，我们将确定组胺对STT神经元的影响， 辣椒素或组织蛋白酶S这些研究将确定是否有两个或更多不同的 灵长类STT中的瘙痒感觉通路。我们最近还发现，抓挠接受者 在对组胺的反应中，STT神经元的视野在几秒钟内抑制了反应，反映了 通过抓挠皮肤瘙痒而产生的舒缓。具体目标2下的研究将确定 抓挠引起的抑制仅依赖于脊髓内的回路或是否有 也是来自大脑的重要贡献。吗啡住院患者给药频繁产生 痒得厉害。这种副作用会限制用于治疗慢性疼痛的吗啡的用量。在特定的目标下 3，我们将确定离子导入应用吗啡是否激活瘙痒和抑制非刺激性 瘙痒(伤害性)STT神经元。我们使用逆行激活技术的结果显示 瘙痒感受性灵长类STT轴突投射到丘脑后部的几个特定核团。在……下面 具体目标4，我们将记录这些丘脑区神经元对组胺注射或 牛舍的应用。我们将识别丘脑瘙痒感觉神经元的皮质投射部位 逆行激活。这些研究将为与瘙痒相关的加工提供重要的新信息 丘脑和大脑皮层的信息。 相关性(请参阅说明)： 拟议的神经生理学实验将进一步加深我们对瘙痒和疼痛感觉的理解 是由脊髓和大脑中不同类型感觉神经元的反应调节的。这 将通过识别中枢神经系统中的感觉过程而有益于公众健康 对患有慢性瘙痒或疼痛的患者进行药理调整。

Itch associated with several conditions can be effectively treated with antihistamines. However itch caused by many conditions, including relatively common dermatological disorders and systemic diseases, can not. These latter types of itch constitute a considerable clinical problem since no effective treatment is currently available. During the previous period of funding, our group has shown that separate populations of primate spinothalamic tract (STT) neurons respond to the itch-producing stimuli intradermal injections of histamine and cowhage, a model of clinically important, non-histaminergic itch. Our results suggest that separate pathways within the CNS carry information regarding histaminergic and non-histaminergic forms of itch. In experiments under Specific Aim 1, we will determine the effects on STT neurons of application of histamine, cowhage, capsaicin, or cathepsin S. These studies will determine whether there are two, or more, distinct pruriceptive pathways within the primate STT. We have also recently found that scratching the receptive fields of STT neurons during a response to histamine inhibited the response for several seconds, mirroring the relief produced by scratching an itchy area of skin. Studies under Specific Aim 2 will determine whether the scratching induced inhibition is dependent solely upon circuitry within the spinal cord or whether there are also important contributions from the brain. Administration of morphine inpatients frequently produces severe itch. This side effect can limit the amount of morphine given to treat chronic pain . Under Specific Aim 3, we will determine whether iontophoretically applied morphine activates pruriceptive and inhibits non- pruriceptive (nociceptive) STT neurons. Our results using antidromic activation techniques revealed that pruriceptive primate STT axons project to several specific nuclei within the posterior thalamus. Under Specific Aim 4, we will record the responses of neurons in these thalamic areas to histamine injections or applications of cowhage. We will identify cortical projection sites of pruriceptive thalamic neurons using antidromic activation. These studies will provide important new information on the processing itch-related information in both the thalamus and cerebral cortex. RELEVANCE (See instructions): The proposed neurophysiological experiments will further our understanding of how itch and pain sensations are mediated by the responses of different types of sensory neurons in the spinal cord and the brain. This will benefit public health by identification of sensory processes in the central nervous system that must be modified pharmacologically in patients suffering from chronic itch or pain.