Willer J C
Laboratoire de neurophysiologie, faculté de médecine Pitié-Salpêtrière, Paris, France.
Neurophysiol Clin. 1990 Nov;20(5):335-56. doi: 10.1016/s0987-7053(05)80203-5.
In the first part of this report a methodology is described which allows an objective and specific exploration of experimental pain in man by using some electrophysiological features of cutaneous reflexes. This method can be summarized as follows: in normal and trained volunteers, we studied simultaneously the recruitment curves of the nociceptive flexion reflex of a knee-flexor muscle (biceps femoris muscle) and that of pain sensation elicited by electrical stimulation of the ipsilateral sural nerve at the ankle. In this procedure, we found that the reflex threshold (Tr) was closely related to that of pain threshold (Tp) around a similar value (10 mA). In the same way, both the threshold of the maximal recruitment of the reflex (Tmr) and that of tolerance to pain (Tpt) were found to be close to 33 mA. These values are reliably reproducible in one subject from one session to the other, and in all subjects with minimal inter-individual variations and without any significant inter-sex difference. These close relationships between Tr and Tp and between Tmr and Tpt respectively constituted the basic ground for the elaboration of the methodology for investigating objectively the human nociceptive reactions. In the second part of the paper, this methodology is applied for studying the spinal mechanisms of morphine analgesia when the drug is given either by intravenous route in normal subjects and in paraplegic patients or administered epidurally in patients with acute postoperative pain. On the one hand, the resulting data strongly validate the model since they show that pain and nociceptive reflex are similarly depressed by morphine in a dose-response fashion. On the other hand, data also show that the spinal level is one of the main important sites of the mechanisms of morphine-induced analgesia since this drug is found to strongly depress selectively the nociceptive transmission directly at the spinal level. Finally, this method is applied for investigating the nociceptive reactions in patients affected either with a pathological lack of pain sensation or, by contrast, in patients complaining of acute or chronic pain from various origins. Since the nociceptive flexion reflex can be considered as a specific and objective physiological correlate of a pain sensation, it can be successfully employed as a useful tool for investigating some aspects of the human nociceptive reactions in both experimental and pathological situations.
在本报告的第一部分，描述了一种方法，该方法通过利用皮肤反射的一些电生理特征，对人体实验性疼痛进行客观且特定的探究。该方法可总结如下：在正常且经过训练的志愿者中，我们同时研究了膝屈肌（股二头肌）的伤害性屈曲反射和通过电刺激同侧踝部腓肠神经所引发的疼痛感觉的募集曲线。在此过程中，我们发现反射阈值（Tr）与疼痛阈值（Tp）在相似值（10毫安）附近密切相关。同样，反射最大募集阈值（Tmr）和疼痛耐受阈值（Tpt）均被发现接近33毫安。这些值在同一受试者的不同实验时段中可可靠重现，且在所有受试者中个体间差异极小，不存在任何显著的性别差异。Tr与Tp以及Tmr与Tpt之间的这些紧密关系分别构成了精心设计客观研究人类伤害性反应方法的基础。在论文的第二部分，当吗啡通过静脉途径给予正常受试者和截瘫患者，或通过硬膜外给药于急性术后疼痛患者时，该方法被用于研究吗啡镇痛的脊髓机制。一方面，所得数据有力地验证了该模型，因为数据表明疼痛和伤害性反射以剂量反应方式被吗啡类似地抑制。另一方面，数据还表明脊髓水平是吗啡诱导镇痛机制的主要重要部位之一，因为发现该药物在脊髓水平直接强烈且选择性地抑制伤害性传递。最后，该方法被用于研究患有病理性痛觉缺失的患者，或者相反，研究抱怨来自各种原因的急性或慢性疼痛的患者的伤害性反应。由于伤害性屈曲反射可被视为疼痛感觉的一种特定且客观的生理关联，它可成功用作在实验和病理情况下研究人类伤害性反应某些方面的有用工具。
