Itch is one of the most primal sensations, being both ubiquitous and important for the well-being of animals. For more than a century, a desire to understand how itch is encoded by the nervous system has prompted the advancement of many theories. Within the past 15 years, our understanding of the molecular and neural mechanisms of itch has undergone a major transformation, and this remarkable progress continues today without any sign of abating. Here I describe accumulating evidence that indicates that itch is distinguished from pain through the actions of itch-specific neuropeptides that relay itch information to the spinal cord. According to this model, classical neurotransmitters transmit, inhibit and modulate itch information in a context-, space- and time-dependent manner but do not encode itch specificity. Gastrin-releasing peptide (GRP) is proposed to be a key itch-specific neuropeptide, with spinal neurons expressing GRP receptor (GRPR) functioning as a key part of a convergent circuit for the conveyance of peripheral itch information to the brain.

痒是最原始的感觉之一，它无处不在，对动物的福祉很重要。一个多世纪以来，对了解神经系统如何编码瘙痒的渴望推动了许多理论的发展。在过去的 15 年里，我们对瘙痒的分子和神经机制的理解发生了重大转变，这一显着的进步一直持续到今天，没有任何减弱的迹象。在这里，我描述了越来越多的证据表明，通过将瘙痒信息传递到脊髓的瘙痒特异性神经肽的作用，可以将瘙痒与疼痛区分开来。根据该模型，经典神经递质以上下文、空间和时间依赖的方式传输、抑制和调节瘙痒信息，但不编码瘙痒特异性。