Molecular Mechanisms of the Itch Sensation in the Spinal Cord

摘要 慢性瘙痒是许多与皮肤、免疫力、 以及神经系统。慢性瘙痒在很大程度上对传统的抗组胺药物具有耐药性，而且 几乎没有有效的治疗方法可用。我们之前已经发现了一小部分瘙痒- 表达瘙痒受体胃泌素释放肽受体(GRPR)的特定神经元在 脊髓。GRPR+神经元是瘙痒感觉所必需的，但不是伤害性感受所必需的 变速箱。我们也开始阐明神经介素B受体(NMBR)的功能， 脊髓中的另一个瘙痒感受器。我们的目标是研究 发痒的传播。我们将利用几个独特的鼠线来检查背部 单细胞水平上的喇叭之痒电路。目标1将确定神经化学、解剖学和 GRPR神经元的电生理特性。我们将检查神经递质 GRPR神经元的表型以及GRPR神经元是投射神经元还是中间神经元 逆行标记。我们还将研究GRPR神经元的电生理特性 采用全细胞膜片钳记录。目标2将确定突触机制 潜在的GRP介导的瘙痒传递。我们将检验GRP引起的假说 GRPR神经元的兴奋是由离子型谷氨酸受体的调制介导的 (IGluRs)和GRP依赖机制在瘙痒原诱导中的不同作用 刺痒性传播。我们还将确定谷氨酸能输入在这一过程中的作用 并检测非组胺能和组胺能瘙痒原是否通过GRP和 IGluRs。目标3将确定瘙痒感觉神经元的分子特性和功能 慢性瘙痒症状。我们将确定在慢性前列腺癌中是否诱导了异位GRPR的表达 通过细胞消融的方法，瘙痒状态依赖于原代GRPR神经元。此外，我们 将表征GRPR神经元在慢性瘙痒条件下的电特性。最后，我们 将使用NMB-Saporin方法研究NMBR神经元在瘙痒感觉中的作用。

Abstract Chronic itch is a presenting sign in numerous diseases associated with the skin, the immune, and the nervous systems. Chronic itch is largely resistant to conventional antihistamines, and few effective therapies are available. We have previously uncovered a small subset of itch- specific neurons which express gastrin-releasing peptide receptor (GRPR), an itch receptor, in the spinal cord. GRPR+ neurons are required for pruritoceptive but not for nociceptive transmission. We have also begun to elucidate the function of neuromedin B receptor (NMBR), another itch receptor in the spinal cord. Our goal is to investigate fundamental mechanisms of itch transmission. We will take advantage of several unique mouse lines to examine the dorsal horn itch circuitry at the single cell level. Aim 1 will determine neurochemical, anatomic and electrophysiological properties of GRPR neurons. We will examine the neurotransmitter phenotype of GRPR neurons and whether GRPR neurons are projection or interneurons by retrograde labeling. We will also examine electrophysiological properties of GRPR neurons using whole cell patch-clamp recording. Aim 2 will determine the synaptic mechanisms underlying GRP-mediated itch transmission. We will test the hypothesis that GRP-evoked excitation of GRPR neurons is mediated by modulation of ionotropic glutamate receptors (iGluRs) and GRP-dependent mechanism is differentially involved in pruritogens-induced pruriceptive transmission. We will also determine the role of glutamatergic input in this process and examine whether nonhistaminergic and histaminergic pruritogen act through GRP and iGluRs. Aim 3 will determine molecular properties and function of itch-sensing neurons in chronic itch condition. We will determine whether ectopic GRPR expression induced in chronic itch condition is dependent on primary GRPR neurons by cell ablation approach. Moreover, we will characterize the electric properties of GRPR neurons in chronic itch condition. Finally, we will examine the role of NMBR neurons in itch sensation using NMB-saporin approach.