(Credit: Image courtesy of Duke University Medical Center)
2012年10月27日 讯 /生物谷BIOON/ --在对触觉研究的同时，来自杜克大学医学中心的研究者指出，特殊的神经元会调节个体的感觉，感觉神经元以刺突为主要特定，基于其容量，其常常决定细胞对压力的敏感性。研究结果是通过对果蝇幼虫研究发现的，刊登于10月25日的国际杂志Current Biology上。该研究首次揭示了感觉神经元的功能，并且为理解人类的慢性疼痛综合征带来了帮助。
研究者W. Daniel Tracey表示，在单一分子水平上，感觉是我们理解的大多数的感知行为，当存在许多触摸感知神经元的时候，我们就不知道到底是哪一种神经元在对压力起反应。研究者对果蝇的幼虫进行研究阐明了触觉的感知，与人类和大多数动物一样，果蝇幼虫也可以通过接触来学习，感知环境、危险以及更多活动等。
为了阐明触觉的效应，研究者用睫毛的顶端来刺果蝇幼虫，同时测定其行为反应以及效应。通过研究，研究者发现了一些特殊的感觉神经元，尤其是2级和3级的多重树突状神经元，对于果蝇的触摸传感器来说，神经元的遗传沉默效应可以损伤感觉效应。
研究者的发现或许为研究动物模型以更好地理解触觉提供基础，Tracey说，我们并不知道是否人类也会出现类似的结构，但是未来研究中我们会对其它物种进行触觉感知的研究。研究者希望更好地理解人类的触觉可以帮助临床医师治疗那些疼痛或者感觉缺失的病人们。
通过学习更多的触觉感知效用，研究者就可以解释为何这些神经元对于刺激变得如此敏感，以及为何这些信号会损伤。或许在未来可以帮助人们理解慢性疼痛时间的发生及其致病的分子机制。相关研究由国家神经性疾病和卒中研究所等机构提供资助。（生物谷Bioon.com）
编译自：Sensory Neurons Identified as Critical to Sense of Touch
doi:10.1016/j.cub.2012.09.019
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PMID:
Dendritic Filopodia, Ripped Pocket, NOMPC, and NMDARs Contribute to the Sense of Touch in Drosophila Larvae
Asako Tsubouchi, Jason C. Caldwell, W. Daniel Tracey
Background Among the Aristotelian senses, the subcellular and molecular mechanisms involved in the sense of touch are the most poorly understood. Results We demonstrate that specialized sensory neurons, the class II and class III multidendritic (md) neurons, are gentle touch sensors of Drosophila larvae. Genetic silencing of these cells significantly impairs gentle touch responses, optogenetic activation of these cells triggers behavioral touch-like responses, and optical recordings from these neurons show that they respond to force. The class III neurons possess highly dynamic dendritic protrusions rich in F-actin. Genetic manipulations that alter actin dynamics indicate that the actin-rich protrusions (termed sensory filopodia) on the class III neurons are required for behavioral sensitivity to gentle touch. Through a genome-wide RNAi screen of ion channels, we identified Ripped Pocket (rpk), No Mechanoreceptor Potential C (nompC), and NMDA Receptors 1 and 2 (Nmdars) as playing critical roles in both behavioral responses to touch and in the formation of the actin-rich sensory filopodia. Consistent with this requirement, reporters for rpk and nompC show expression in the class III neurons. A genetic null allele of rpk confirms its critical role in touch responses. Conclusions Output from class II and class III md neurons of the Drosophila larvae is necessary and sufficient for eliciting behavioral touch responses. These cells show physiological responses to force. Ion channels in several force-sensing gene families are required for behavioral sensitivity to touch and for the formation of the actin-rich sensory filopodia.
