Itch and Pain Differences and Commonalities
Itch and Pain Differences and Commonalities
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DOI：
10.1007/978-3-662-46450-2_14
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发表时间：
2015-01-01
期刊：
影响因子：
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通讯作者：
Schmelz, Martin
中科院分区：
文献类型：
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作者：
Schmelz, Martin
疼痛和瘙痒通常被认为是对立的，因为疼痛刺激如抓挠抑制瘙痒。此外，阿片类药物对疼痛加工的抑制产生瘙痒，进一步支持了它们的对立作用。瘙痒和疼痛加工的不同特定途径已经被发现，并且在小鼠中建立了一些分子标记，这些分子标记在初级传入和脊髓水平上识别参与组胺能和非组胺能瘙痒加工的神经元。这些结果与瘙痒的特异性理论一致，可能表明疼痛和瘙痒应该在神经元、介质和机制的水平上分开研究。然而，除了广泛重叠的瘙痒和疼痛介质外，也有证据表明初级传入事件的功能重叠：当表皮局部激活时，伤害性初级传入事件可以引起瘙痒，并且在志愿者局部神经生长因子应用后发现伤害感受器和痛觉感受器都增敏。因此，慢性瘙痒和疼痛发生的机制，包括原发性传入神经的自发活动和致敏，以及脊髓致敏，可能在很大程度上重叠。因此，研究概念应该解决共同的机制，而不是将瘙痒和疼痛分开。这种方法似乎最适合临床条件的神经性瘙痒和疼痛，也慢性炎症条件。虽然瘙痒研究人员可以从疼痛领域的大量信息中受益，但疼痛研究人员会发现，自发瘙痒的行为读数比动物自发疼痛的行为读数要简单得多，而且作为瘙痒活动来源的皮肤甚至在患者身上也更容易获得。
Pain and itch are generally regarded antagonistic as painful stimuli such as scratching suppresses itch. Moreover, inhibition of pain processing by opioids generates itch further supporting their opposing role. Separate specific pathways for itch and pain processing have been uncovered, and several molecular markers have been established in mice that identify neurons involved in the processing of histaminergic and non-histaminergic itch on primary afferent and spinal level. These results are in agreement with the specificity theory for itch and might suggest that pain and itch should be investigated separately on the level of neurons, mediators, and mechanisms. However, in addition to broadly overlapping mediators of itch and pain, there is also evidence for overlapping functions in primary afferents: nociceptive primary afferents can provoke itch when activated very locally in the epidermis, and sensitization of both nociceptors and pruriceptors has been found following local nerve growth factor application in volunteers. Thus, also mechanisms that underlie the development of chronic itch and pain including spontaneous activity and sensitization of primary afferents as well as spinal cord sensitization may well overlap to a great extent. Rather than separating itch and pain, research concepts should therefore address the common mechanisms. Such an approach appears most appropriate for clinical conditions of neuropathic itch and pain and also chronic inflammatory conditions. While itch researchers can benefit from the large body of information of the pain field, pain researchers will find behavioral readouts of spontaneous itch much simpler than those for spontaneous pain in animals and the skin as source of the pruritic activity much more accessible even in patients.