Department of Neurology, Erasmus MC, Rotterdam, The Netherlands.
Neuroscientist. 2012 Feb;18(1):8-14. doi: 10.1177/1073858410391813. Epub 2011 Feb 28.
Nociceptive stimuli are transmitted through thinly myelinated or unmyelinated primary afferent fibers called nociceptors, which terminate mainly in the superficial dorsal horn of the spinal cord. While most nociceptive fibers terminate in the spinal segment of the entrance, (collateral) fibers may ascend and descend several segments upon their entry into the spinal cord, which is reflected in the receptive fields of central nociceptive neurons. In chronic pain states like inflammatory or neuropathic pain, the area of nociceptive activity may expand even further in rostrocaudal and mediolateral directions. Also, within minutes (inflammatory pain) or days (neuropathic pain), an increased sensitivity of peripheral and central nociceptive neurons will develop, which is referred to as sensitization. While anatomical, physiological, and psychophysical techniques have focused on one particular aspect of central sensitization at a time, functional imaging techniques like functional MRI, intrinsic optical imaging, and autofluorescent flavoprotein imaging (AFI) are able to capture both spatial and temporal dimensions of central sensitization simultaneously. AFI and other neuroimaging techniques may clarify fundamental aspects relating to the spread of nociceptive activity within the spinal cord and may thus provide a practical tool to test the efficacy of new analgesic drugs or procedures in animals and ultimately in humans.
伤害性刺激通过薄髓或无髓的初级传入纤维（称为伤害感受器）传递，主要终止于脊髓的浅层背角。虽然大多数伤害性纤维终止于进入的脊髓节段，但（侧支）纤维在进入脊髓后可能上升和下降几个节段，这反映在中枢伤害性神经元的感受野中。在慢性疼痛状态，如炎症性或神经性疼痛中，伤害性活动的区域可能在头尾部和内外侧方向进一步扩大。此外，在外周和中枢伤害性神经元中，敏感性会在几分钟（炎症性疼痛）或几天（神经性疼痛）内增加，这被称为敏化。虽然解剖学、生理学和心理物理学技术一次只关注中枢敏化的一个特定方面，但功能成像技术，如功能性磁共振成像、内源性光学成像和自发荧光黄素蛋白成像（AFI），能够同时捕捉中枢敏化的空间和时间维度。AFI 和其他神经影像学技术可以阐明与脊髓内伤害性活动传播相关的基本方面，因此可能为在动物中测试新的镇痛药物或程序的疗效提供实用工具，并最终在人类中提供工具。
