Department of Oral & Maxillofacial Surgery, School of Clinical Dentistry, Claremont Crescent, Sheffield S10 2TA, UK.
J Physiol. 2010 Jan 1;588(Pt 1):117-24. doi: 10.1113/jphysiol.2009.181511. Epub 2009 Nov 23.
It has been suggested that primary afferent C-fibres that respond to innocuous tactile stimuli are important in the sensation of pleasurable touch. Although it is known that C-tactile fibres terminate in the substantia gelatinosa (lamina II) of the spinal cord, virtually all of the neurons in this region are interneurons, and currently it is not known how impulses in C-mechanoreceptors are transmitted to higher centres. In the current study, I have tested the quantitative response properties of 'wide dynamic range' projection neurons in lamina I of the spinal cord to graded velocity brushing stimuli to identify whether low-threshold mechanoreceptor input to these neurons arises from myelinated or umyelinated nerve fibres. Graded velocity brushing stimuli (6.6-126 cm s(-1)) were used to characterize the mechanoreceptor inputs to 'wide dynamic range' neurons in lamina I of the dorsal horn that had axons that projected to the contralateral parabrachial nucleus. The most effective tactile stimuli for activation of 'wide dynamic range' lamina I spinoparabrachial neurons were low velocity brush strokes: peak discharge occurred at a mean velocity of 9.2 cm s(-1) (range 6.6-20.4 cm s(-1), s.d. 5.0 cm s(-1)), and declined exponentially as brush velocity increased. The data indicate that C-fibres, but not A-fibres, conveyed low-threshold mechanoreceptor inputs to lamina I projection neurons.
有人提出，对无害触觉刺激产生反应的初级传入 C 纤维在愉悦触摸感中起着重要作用。虽然已知 C 触觉纤维终止于脊髓的胶状质（II 层），但该区域的几乎所有神经元都是中间神经元，目前尚不清楚 C 机械感受器的冲动如何传递到更高的中枢。在目前的研究中，我测试了脊髓 I 层中“宽动态范围”投射神经元对分级速度刷刺激的定量反应特性，以确定这些神经元的低阈值机械感受器输入是否来自有髓或无髓神经纤维。使用分级速度刷刺激（6.6-126 cm s(-1)) 来描述投射到对侧臂旁核的背角 I 层中“宽动态范围”神经元的机械感受器输入。最有效的触觉刺激是激活“宽动态范围”I 层脊髓-臂旁神经元的低速度刷刺激：峰值放电发生在平均速度为 9.2 cm s(-1)（范围 6.6-20.4 cm s(-1)，s.d. 5.0 cm s(-1)），随着刷速度的增加呈指数下降。数据表明，C 纤维而不是 A 纤维向 I 层投射神经元传递低阈值机械感受器输入。
