Naugle Kelly M, Cruz-Almeida Yenisel, Vierck Charles J, Mauderli Andre P, Riley Joseph L
Pain Research and Intervention Center of Excellence, College of Dentistry, University of Florida, P.O. Box 103628, Gainesville, FL 32611, USA.
Pain Research and Intervention Center of Excellence, College of Medicine, University of Florida, 2004 Mowry Road, Gainesville, FL 32611, USA.
Behav Brain Res. 2015 Aug 1;289:61-8. doi: 10.1016/j.bbr.2015.04.014. Epub 2015 Apr 20.
The current study evaluated age differences in conditioned pain modulation using a test stimulus that provided the opportunity to evaluate changes in heat pain sensitivity, sensitization, and desensitization within the same paradigm. During this psychophysical test, pain intensity clamping uses REsponse Dependent STIMulation (REDSTIM) methodology to automatically adjust stimulus intensity to maintain a desired pain rating set-point. Specifically, stimulus intensity increases until a pre-defined pain rating (the setpoint) is exceeded, and then decreases until pain ratings fall below the setpoint, with continued increases and decreases dictated by ratings. The subjects are blinded in terms of the setpoint and stimulus intensities. Younger and older subjects completed two test sessions of two REDSTIM trials, with presentation of conditioning cold stimulation between the trials of one session but not the other. The results indicated that conditioning cold stimulation similarly decreased the overall sensitivity of younger and older subjects, as measured by the average temperature that maintained a setpoint rating of 20 (on a scale of 0-100). The conditioning stimulus also significantly enhanced sensitization following ascending stimulus progressions and desensitization following descending stimulus progressions in older subjects relative to younger subjects. Thus, older subjects experienced greater swings in sensitivity in response to varying levels of painful stimulation. These results are discussed in terms of control over pain intensity by descending central modulatory systems. These findings potentially shed new light on the central control over descending inhibition and facilitation of pain.
本研究使用一种测试刺激评估了条件性疼痛调制中的年龄差异，该测试刺激提供了在同一范式内评估热痛敏感性、敏化和脱敏变化的机会。在这项心理物理学测试中，疼痛强度钳制采用响应依赖刺激（REDSTIM）方法自动调整刺激强度，以维持所需的疼痛评分设定点。具体而言，刺激强度会增加，直到超过预定义的疼痛评分（设定点），然后降低，直到疼痛评分低于设定点，随后根据评分持续增减。受试者对设定点和刺激强度不知情。年轻和年长受试者完成了两个包含两次REDSTIM试验的测试环节，其中一个环节的两次试验之间会施加条件性冷刺激，而另一个环节则不会。结果表明，通过维持20（0 - 100评分量表）设定点评分的平均温度来衡量，条件性冷刺激同样降低了年轻和年长受试者的总体敏感性。相对于年轻受试者，条件性刺激在年长受试者中还显著增强了刺激强度上升后的敏化以及刺激强度下降后的脱敏。因此，年长受试者在对不同程度疼痛刺激的反应中，敏感性波动更大。本文根据下行中枢调节系统对疼痛强度的控制对这些结果进行了讨论。这些发现可能为下行抑制和疼痛易化的中枢控制带来新的启示。
