Rossi Simone, della Volpe Raimondo, Ginanneschi Federica, Ulivelli Monica, Bartalini Sabina, Spidalieri Raffaele, Rossi Alessandro
Dipartimento di Neuroscienze, Sezione Neurologia, U.O. Neurofisiopatologia, Università di Siena, Policlinico Le Scotte, Viale Bracci, I-53100 Siena, Italy.
Clin Neurophysiol. 2003 Jul;114(7):1351-8. doi: 10.1016/s1388-2457(03)00073-7.
It is known that tonic muscle pain induced by a Levo-Ascorbic (L-AS) solution injected in a foot muscle can transiently modify both regional proprioception and stimulus perception. These findings are paralleled by changes of middle-latency lower-limb somatosensory evoked potentials (SEPs). However, little is known on the behaviourally relevant aspect whether eventual SEP pain-induced changes could be partly due to a sort of 'motor strategy' of subjects in the frame of a self-protective reaction towards the noxious stimulus. Movement and imagery of movements are in fact known to reduce mainly pre-central SEP amplitude (i.e. gating effect).
Low-threshold afferents ulnar SEPs, psychophysical pain ratings and fingers' position sense were monitored in the time-course during L-AS injection in the right first dorsal interosseous muscle. Control experiments included SEPs (either following prevalent ulnar nerve low-threshold afferent stimulation or more conventional mixed nerve stimulation) during actual movements execution and imagery of movements of the right hand.
Tonic pain induced a significant reduction of the post-central N(20)-P(25)-N(33) complex and a significant increase of the N(18) wave. These changes, that were paralleled by distortion of the finger position sense, were delayed 2-5 min with respect to the maximal subjective pain sensation. Conversely, movement imagery tasks lead to a significant, selective, reduction of the pre-central N(30) complex. This wave was even more reduced during actual movements, in combination with a reduction of those post-central components peaking after the first activation of the primary sensory cortex.
Early sensory processing at cortical level is changed during tonic muscle pain, mainly for those components which may be theoretically involved in proprioceptive afferent elaboration. These changes are likely not due to subconscious or voluntary motor strategies of the subjects in the frame of a self-protective aversive reaction towards the noxious stimulus.
已知向足部肌肉注射左旋抗坏血酸（L-AS）溶液所诱发的强直性肌肉疼痛可短暂改变局部本体感觉和刺激感知。这些发现与中潜伏期下肢体感诱发电位（SEP）的变化相似。然而，关于行为相关方面，即最终SEP疼痛诱发的变化是否可能部分归因于受试者在对有害刺激的自我保护反应框架内的某种“运动策略”，我们知之甚少。事实上，已知运动和运动想象主要会降低中央前SEP波幅（即门控效应）。
在向右侧第一背侧骨间肌注射L-AS的过程中，监测尺神经低阈值传入SEP、心理物理学疼痛评分和手指位置觉的时间进程。对照实验包括在实际运动执行和右手运动想象过程中的SEP（要么是在主要尺神经低阈值传入刺激后，要么是更传统的混合神经刺激后）。
强直性疼痛导致中央后N（20）-P（25）-N（33）复合波显著降低，N（18）波显著增加。这些变化与手指位置觉的扭曲同时出现，相对于最大主观疼痛感觉延迟了2 - 5分钟。相反，运动想象任务导致中央前N（30）复合波显著、选择性地降低。在实际运动过程中，该波幅降低得更多，同时中央后那些在初级感觉皮层首次激活后达到峰值的成分也降低。
在强直性肌肉疼痛期间，皮质水平的早期感觉处理发生改变，主要是对于那些理论上可能参与本体感觉传入加工的成分。这些变化可能不是由于受试者在对有害刺激的自我保护厌恶反应框架内的潜意识或自主运动策略所致。
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