Itch neurons studied in vivo

描述（由申请人提供）：慢性瘙痒与慢性疼痛一样，在临床上被认为是痛苦和生活质量下降的主要原因。虽然瘙痒伴随着许多神经，皮肤和全身性疾病，但在潜在的外周神经机制的研究中，它受到的关注不如疼痛。有两种一般的方法来研究背根神经节神经元的生理特性，这些神经元对引起人类瘙痒或动物瘙痒相关行为的化学刺激作出反应。第一种是电生理记录这些神经元对应用于其皮肤感受野的化学物质的反应中诱发的动作电位。第二种方法是使用细胞体（索马），解离并放置在培养物中，作为外周终末的模型来检查化学感觉转导的细胞分子机制。在这个模型的测试中，我们将联合收割机这两种方法和比较的反应特性的索马和感受野在完整的，可视化的，伤害性DRG神经元，在体内。我们将使用遗传分子荧光标记来识别麻醉小鼠中特定类型DRG神经元的索马。将从索马细胞外记录动作电位，以响应递送至其皮肤感受野的刺激和痛觉刺激。然后，将激活感受野的刺激性化学物质局部应用于索马，并测量体膜兴奋性或细胞内钙的变化。为了比较，将从具有相同荧光标记的急性解离的胞体获得类似的测量。如果成功，结果将指向研究瘙痒介导化学物质如何在外周神经元中感知的潜在细胞机制的新方法，这是开发药物的重要先导，这些药物将专门用于阻断人类的病理性瘙痒。 公共卫生相关性：该实验将测试一种新的生理制剂的可行性，该制剂将允许在功能鉴定的外周感觉神经元中进行化学诱发瘙痒的细胞分子研究。该方法是使用遗传分子标记来识别感觉神经元的特定亚型，并在体内和体外使用电生理记录和钙成像方法来确定其功能特性。结果将指出研究瘙痒介导化学物质如何在外周神经元中感知的潜在细胞机制的新方法，这是开发专门用于阻断人类病理性瘙痒的药物的重要先导。

DESCRIPTION (provided by applicant): Chronic itch, like chronic pain, is clinically recognized as a major cause of suffering and loss in the quality of life. Although itch accompanies many neurological, dermatological and systemic diseases, it has received less attention than pain in studies of underlying peripheral neural mechanisms. There have been two general approaches to studying the physiological properties of dorsal root ganglion neurons that respond to chemical stimuli that evoke itch in humans or itch-associated behavior in animals. The first is to electrophysiologically record action potentials evoked in these neurons in response to a pruritic chemical applied to their cutaneous receptive fields. The second approach is to examine the cellular molecular mechanisms of chemical sensory transduction using the cell body (soma), dissociated and placed in culture, as a model of the peripheral terminal endings. In a test of this model, we will combine these two approaches and compare the response properties of the soma and the receptive field in the intact, visualized, nociceptive DRG neuron, in vivo. We will use genetic-molecular fluorescent markers to identify the soma of a particular type of DRG neuron in the anesthetized mouse. Action potentials will be recorded extracellularly from the soma in response to pruritic and algesic stimuli delivered to its cutaneous receptive field. Then pruritic chemicals that activated the receptive field will be topically applied to the soma and alterations in somal membrane excitability or intracellular calcium will be measured. Similar measurements will be obtained, for comparison, from acutely dissociated somas with the same fluorescent markers. If successful, the outcome will point to new methods of studying the underlying cellular mechanisms of how itch mediating chemicals are sensed in peripheral neurons, an important precursor to the development of drugs that will act specifically to block pathological itch in humans. PUBLIC HEALTH RELEVANCE: The experiments will test the feasibility of a new physiological preparation that will allow cellular-molecular studies of chemically evoked itch to be carried out in functionally identified peripheral sensory neurons, in vivo. The approach is to use genetic-molecular markers to identify specific subtypes of sensory neurons and use electrophysiological recording and calcium imaging methods both in vivo and also in vitro to determine their functional properties. The outcome will point to new methods of studying the underlying cellular mechanisms of how itch mediating chemicals are sensed in peripheral neurons, an important precursor to the development of drugs that will act specifically to block pathological itch in humans.