LaBuda C J, Fuchs P N
The University of Texas at Arlington, Psychology Department, TX 76019, USA.
Neuroscience. 2005;136(1):311-22. doi: 10.1016/j.neuroscience.2005.07.010.
The affective and the sensory dimensions of pain processing can be differentiated in humans through the use of questionnaires and verbal communication. It is difficult to dissociate these two components of pain processing in rodents, and an understanding of the underlying mechanisms for each component is unclear. The quantification of a novel behavioral response to a repeated noxious cutaneous stimulus together with a measurement of tactile allodynia in nerve-injured rats might be used to differentially explore the sensory and affective components of pain processing in the rat. The present study utilized electrical stimulation of the anterior cingulate cortex, a structure implicated in affective pain processing but not sensory processing, in nerve-injured rats (L5 spinal nerve ligation) and found that the aversive quality of noxious cutaneous hindpaw stimulation was attenuated. There were no effects on sensory processing, because anterior cingulate cortex stimulation did not produce an anti-allodynic effect in L5 spinal nerve ligation animals. Furthermore, anterior cingulate cortex stimulation in animals with bilateral ventrolateral periaqueductal gray area lesions did not affect tactile sensitivity in L5 spinal nerve ligation rats, indicating that an endogenous pain suppression system was not likely activated by anterior cingulate cortex stimulation. However, bilateral ventrolateral periaqueductal gray area lesions in L5 spinal nerve ligation rats blocked the effect produced by anterior cingulate cortex stimulation in the place escape/avoidance paradigm. Specifically, these animals avoided noxious stimulation of the allodynic paw significantly more than anterior cingulate cortex-stimulated, sham or incomplete ventrolateral periaqueductal gray area-lesioned, L5 spinal nerve ligation animals. These findings provide the first quantified report that the activation of the anterior cingulate cortex reduced the aversive quality of repeated noxious tactile stimulation in nerve-injured animals without interfering with normal sensory processing. This effect might require the presence of an intact ventrolateral periaqueductal gray area. It is concluded that the selective manipulation of the anterior cingulate cortex has different effects on pain affect and sensory processing in a rodent model of neuropathic pain.
通过使用问卷和言语交流，人类疼痛处理的情感维度和感觉维度可以区分开来。在啮齿动物中，很难区分疼痛处理的这两个组成部分，而且对于每个组成部分的潜在机制尚不清楚。对神经损伤大鼠重复有害皮肤刺激的一种新行为反应进行量化，并测量触觉异常性疼痛，可能用于分别探索大鼠疼痛处理的感觉和情感成分。本研究对神经损伤大鼠（L5 脊髓神经结扎）进行前扣带回皮质电刺激，前扣带回皮质是一个与情感性疼痛处理有关但与感觉处理无关的结构，结果发现有害的后爪皮肤刺激的厌恶性质减弱。对感觉处理没有影响，因为前扣带回皮质刺激在 L5 脊髓神经结扎动物中未产生抗异常性疼痛作用。此外，双侧腹外侧导水管周围灰质区损伤动物的前扣带回皮质刺激对 L5 脊髓神经结扎大鼠的触觉敏感性没有影响，这表明前扣带回皮质刺激不太可能激活内源性疼痛抑制系统。然而，L5 脊髓神经结扎大鼠的双侧腹外侧导水管周围灰质区损伤在位置逃避/回避范式中阻断了前扣带回皮质刺激产生的效应。具体而言，这些动物比接受前扣带回皮质刺激、假手术或腹外侧导水管周围灰质区不完全损伤的 L5 脊髓神经结扎动物更显著地避免对异常性疼痛爪子的有害刺激。这些发现提供了第一份量化报告，即前扣带回皮质的激活降低了神经损伤动物重复有害触觉刺激的厌恶性质，而不干扰正常的感觉处理。这种效应可能需要完整的腹外侧导水管周围灰质区存在。得出的结论是，在前神经病理性疼痛啮齿动物模型中，前扣带回皮质的选择性操纵对疼痛情感和感觉处理有不同影响。
