Mason Andrew G, van der Glas Hilbert W, Scott Brendan J J, Cadden Samuel W
Oral Neurophysiology Research Group, The Dental School, University of Dundee, Dundee, DD1 4HN, UK.
Exp Brain Res. 2007 Sep;182(1):81-91. doi: 10.1007/s00221-007-0972-6. Epub 2007 May 22.
In human beings, inhibitory jaw reflexes can be depressed by painful stimulation of remote parts of the body. Since similar effects can be produced by the stress of anticipating pain, we wished to investigate whether the effects of remote painful stimuli are dependent on stress. EMG recordings were made from a masseter muscle while subjects maintained activity in the muscle at approximately 12.5% of maximum using visual feedback. The protocols involved three sequences: (1) "standard controls" in which reflexes were evoked by electrical test stimuli applied to the upper lip; (2) "standard conditioning" in which painful electrical conditioning stimuli were applied over the sural nerve 100 ms before the test stimuli; (3) "random sequences" in which test-only and conditioning-test combinations were employed in a double-blind, random, order. Data are presented as means +/- SEMs. In the standard controls, the stimuli evoked clear inhibitory reflexes (latency 37 +/- 1.3 ms, duration 62 +/- 5.6 ms; n = 10) in all the subjects. During standard conditioning, the reflex magnitude was reduced significantly (by 50.0 +/- 8.5%, P = 0.0002, one-sample t-test). When the test-only and conditioning-test responses were extracted from the random sequences, there was also a significant reduction in the reflex magnitude following conditioning (by 34.6 +/- 5.5%, P = 0.0002, one-sample t-test) albeit less so than between the standard sequences (P = 0.03, paired t-test). A second series of experiments suggested that these lesser effects during the random sequences were not substantially due to any loss of temporal summation of the conditioning mechanisms. The evidence for this was that application of pairs of conditioning stimuli did not produce a significantly greater effect than single conditioning stimuli within a random sequence (39.9 +/- 9.6% as opposed to 32.7 +/- 9.1% reductions in the reflex, P = 0.117, paired t-test). Therefore since any stress in the random sequences would not have been "tied" to the conditioned responses alone, the effects of remote painful stimuli on this inhibitory jaw reflex cannot be entirely secondary to stress.
在人类中，对身体远处部位的疼痛刺激可抑制下颌反射。由于预期疼痛的压力也能产生类似效果，我们希望研究远处疼痛刺激的效果是否依赖于压力。在受试者利用视觉反馈将咬肌活动维持在最大活动量的约12.5%时，记录咬肌的肌电图。实验方案包括三个序列：(1)“标准对照”，通过对上唇施加电测试刺激来诱发反射；(2)“标准条件反射”，在测试刺激前100毫秒对腓肠神经施加疼痛性电条件刺激；(3)“随机序列”，采用仅测试和条件刺激-测试组合，以双盲、随机顺序进行。数据以平均值±标准误表示。在标准对照中，刺激在所有受试者中均诱发了明显的抑制性反射（潜伏期37±1.3毫秒，持续时间62±5.6毫秒；n = 10）。在标准条件反射期间，反射幅度显著降低（降低50.0±8.5%，P = 0.0002，单样本t检验）。当从随机序列中提取仅测试和条件刺激-测试反应时，条件反射后反射幅度也显著降低（降低34.6±5.5%，P = 0.0002，单样本t检验），尽管降低幅度小于标准序列之间的差异（P = 0.03，配对t检验）。另一系列实验表明，随机序列中这些较小的效应并非主要由于条件反射机制的时间总和丧失。证据是，在随机序列中，成对施加条件刺激所产生的效应并不比单个条件刺激显著更大（反射降低分别为39.9±9.6%和32.7±9.1%，P = 0.117，配对t检验）。因此，由于随机序列中的任何压力并非仅与条件反应“相关联”，远处疼痛刺激对这种抑制性下颌反射的影响不能完全归因于压力。
