Mason Andrew G, Newton James P, Cadden Samuel W
Oral Neurophysiology Research Group, The Dental School, University of Dundee, Dundee, UK.
Eur J Oral Sci. 2007 Oct;115(5):371-7. doi: 10.1111/j.1600-0722.2007.00470.x.
In humans, inhibitory jaw reflexes can be depressed by painful stimulation of remote parts of the body. The underlying mechanisms may involve diffuse noxious inhibitory controls (DNIC). Animal experiments have shown that the neurons which may mediate DNIC show spatial encoding (i.e. their responses vary in relation to the size of the body area being stimulated). The aim of this study was to investigate whether the modulation of an inhibitory jaw reflex shows similar spatial dependency. Electromyographic recordings were made in 9 subjects, from a masseter muscle that was activated to a level equivalent to 10% of that obtained during a maximum voluntary contraction. Reflex inhibitions were evoked by electrical stimuli to the upper lip, either alone (controls) or during the application of conditioning stimuli (47 degrees C water) to the fingers, the hand, the half forearm or the whole forearm. Conditioning stimuli applied to the larger but not to the smaller areas resulted in significant modulations of the reflex. There was a significant correlation between stimulus area and reflex magnitude. These results demonstrate a spatial dependency for the modulation of an inhibitory jaw reflex by painful stimuli -- a further parallel with DNIC as studied on single neurons in animals.
在人类中，抑制性下颌反射可因对身体其他部位的疼痛刺激而受到抑制。其潜在机制可能涉及弥散性伤害性抑制控制（DNIC）。动物实验表明，可能介导DNIC的神经元表现出空间编码（即它们的反应因受刺激身体区域的大小而异）。本研究的目的是调查抑制性下颌反射的调制是否表现出类似的空间依赖性。对9名受试者的咬肌进行肌电图记录，使咬肌激活至相当于最大自主收缩时所获水平10%的程度。通过对上唇进行电刺激诱发反射抑制，刺激可单独进行（对照组），也可在对手指、手部、半侧前臂或整个前臂施加条件刺激（47摄氏度的水）时进行。对较大区域而非较小区域施加条件刺激会导致反射的显著调制。刺激区域与反射幅度之间存在显著相关性。这些结果证明了疼痛刺激对抑制性下颌反射调制的空间依赖性——这是与在动物单个神经元上研究的DNIC的又一相似之处。
