Science：发现瘙痒神经元

据2009年8月7日的《科学》杂志报道说，科学家们已经查明了小鼠体内的一组对瘙痒刺激进行反应的神经元，改组神经元会通知脑部现在是开始瘙抓的时侯了。 这些发现本身也挠到了神经科学的一个长期的痒处：即神经系统是否对痛觉和瘙痒的感觉以同样的方式进行处置。

研究人员对瘙痒是否基本上不过是疼痛的一种形式或体内是否有专门的瘙痒、疼痛及其它感觉（即所谓的“标示线路假设”）的神经通路进行过辩论。 迄今为止，有关这一假说的证据仍然不甚一致，但由Yan-Gang Sun所做的一项新的研究应该有助于息止这一争议。 研究人员过去曾经确认了一种叫做GRPR的神经元受体是感受瘙痒刺激但却不感受疼痛刺激的受体。

现在，这些研究人员证明，那些脊髓中缺乏GRPR受体神经元的小鼠不会对瘙痒刺激进行挠抓反应，但它们感受疼痛的能力则与正常小鼠一样。 这类表达GRPR的神经元结果发现与另外一组叫做SST的神经元是不同的，而这曾经是人们过去争辩的焦点。 这些新的发现因而提示，表达GRPR的神经元是一个人们长期以来寻找的脊髓中的瘙痒感觉“标示线路”的组成成分。

原始出处：

Science DOI: 10.1126/science.1174868

Cellular Basis of Itch Sensation

Yan-Gang Sun 1, Zhong-Qiu Zhao 1, Xiu-Li Meng 2, Jun Yin 1, Xian-Yu Liu 1, Zhou-Feng Chen 1*

1 Departments of Anesthesiology, Psychiatry, and Developmental Biology, Washington University School of Medicine Pain Center, St. Louis, MO 63110, USA.
2 Departments of Anesthesiology, Psychiatry, and Developmental Biology, Washington University School of Medicine Pain Center, St. Louis, MO 63110, USA.; Department of Anesthesiology, Peking University Third Hospital, Beijing 100191, P.R. China.

Itch and pain are two distinct sensations. Although our previous study suggested that gastrin-releasing peptide receptor (GRPR) is an itch-specific gene in the spinal cord, a long-standing question of whether there are separate neuronal pathways for itch and pain remains unsettled. Here, we selectively ablated lamina I neurons expressing GRPR in the spinal cord of mice. These mice showed profound scratching deficits in response to all of the itching (pruritogenic) stimuli tested, irrespective of their histamine-dependence. In contrast, pain behaviors were unaffected. Our data also suggest that GRPR+ neurons are different from the spinothalamic tract (STT) neurons that have been the focus of the debate. Together, the present study suggests that GRPR+ neurons constitute a long-sought labeled line for itch sensation in the spinal cord.