Meyer R A, Davis K D, Cohen R H, Treede R D, Campbell J N
Department of Neurosurgery, Johns Hopkins University, Baltimore, MD 20723.
Brain Res. 1991 Oct 11;561(2):252-61. doi: 10.1016/0006-8993(91)91601-v.
A problem in the study of nociceptors is that intense stimuli are used to locate the receptive field (RF), and thus the receptor may be damaged before the first responses are recorded. In addition, some nociceptors do not respond to the mechanical stimuli often used to search for the RF. To overcome these problems, an electrical search technique was developed to locate the RF of cutaneous nociceptors. In the hairy skin of anesthetized monkey, we used this technique to locate the RF of 63 A delta-fibers and 22 C-fibers that had extremely high thresholds or were unresponsive to mechanical stimuli. We refer to these afferents as mechanically insensitive afferents (MIAs). Ten A delta-fiber MIAs had a short latency response to stepped heat stimuli and could be responsible for first pain sensation. Five A delta-fiber MIAs and one C-fiber MIA did not respond to mechanical or heat stimuli but did respond to injection into the electrical RF of an artificial inflammatory soup containing histamine, bradykinin, prostaglandin E1, and serotonin. These chemoreceptors might be responsible for the pain and itch sensations that result from chemical stimuli. Some MIAs became more responsive to mechanical stimuli after injection into the RF of the inflammatory soup and, thus, may contribute to the hyperalgesia to mechanical stimuli associated with cutaneous injury. A large proportion of the A delta-fiber (48%) and C-fiber (30%) afferents in this study were insensitive to mechanical stimuli. The role of these MIAs in sensation needs to be studied further. The electrical search technique enables a systematic study of these afferents to be performed. This technique may also be of use to identify and characterize dorsal horn neurons that have inputs from MIAs.
伤害感受器研究中的一个问题是，人们使用强烈刺激来定位感受野（RF），这样一来，感受器可能在记录到最初反应之前就已受损。此外，一些伤害感受器对常用于寻找感受野的机械刺激没有反应。为了克服这些问题，人们开发了一种电搜索技术来定位皮肤伤害感受器的感受野。在麻醉猴的有毛皮肤上，我们使用这种技术定位了63条Aδ纤维和22条C纤维的感受野，这些纤维具有极高的阈值或对机械刺激无反应。我们将这些传入纤维称为机械不敏感传入纤维（MIA）。10条Aδ纤维MIA对阶梯式热刺激有短潜伏期反应，可能负责第一痛觉。5条Aδ纤维MIA和1条C纤维MIA对机械或热刺激无反应，但对注射到包含组胺、缓激肽、前列腺素E1和5-羟色胺的人工炎性介质溶液的电感受野中有反应。这些化学感受器可能是化学刺激引起的疼痛和瘙痒感觉的原因。一些MIA在注射炎性介质溶液到感受野后对机械刺激的反应增强，因此可能促成与皮肤损伤相关的对机械刺激的痛觉过敏。本研究中很大一部分Aδ纤维（48%）和C纤维（30%）传入纤维对机械刺激不敏感。这些MIA在感觉中的作用需要进一步研究。电搜索技术使得能够对这些传入纤维进行系统研究。该技术也可能有助于识别和表征从MIA接收输入的背角神经元。
