Palecek J, Willis D W
Department of Anatomy and Neurosciences, Marine Biomedical Institute, The University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1069, USA Institute of Physiology ASCR, Praha 142 20, Czech Republic.
Pain. 2003 Aug;104(3):501-507. doi: 10.1016/S0304-3959(03)00075-7.
Recent clinical studies have demonstrated that a midline lesion of the dorsal columns (DC, limited midline myelotomy) reduces pain of visceral origin in patients with pelvic cancer. Animal experiments showed that a DC lesion leads to decreased activation of thalamic neurons by visceral stimuli, lowers the impact of noxious colon stimulation in behavioral tests and suggested that the effect is mediated mainly by postsynaptic DC neurons. In the present experiments we examined the effect of bilateral DC or ventrolateral (VL) spinal cord lesions on visceromotor reflex EMG activity evoked by graded colorectal distention (30, 60, 80 mmHg) under control conditions and after colon inflammation with mustard oil. The colon inflammation increased significantly the visceromotor responses so that the response to a 30 mmHg distention was larger than that produced by 80 mmHg before inflammation. The DC lesion did not affect the visceromotor reflex response under control conditions but reduced the increased responses after colon inflammation back to control levels and prevented the potentiation of the reflex responses by colon inflammation when performed before the inflammation. Our results suggest that the role of the DC pathway in transmission of visceral pain is augmented under inflammatory conditions when symptoms of visceral allodynia and hyperalgesia may be present. The VL lesions eliminated the visceromotor reflex, presumably by interrupting a facilitatory pathway that involves the brain stem.
近期的临床研究表明，背柱中线损伤（背柱，有限的中线脊髓切开术）可减轻盆腔癌患者内脏源性疼痛。动物实验显示，背柱损伤会导致丘脑神经元对内脏刺激的激活减少，降低有害结肠刺激在行为测试中的影响，并表明该效应主要由突触后背柱神经元介导。在本实验中，我们研究了双侧背柱或脊髓腹外侧（VL）损伤对在对照条件下以及用芥子油诱发结肠炎症后，由不同程度结肠扩张（30、60、80 mmHg）诱发的内脏运动反射肌电图活动的影响。结肠炎症显著增加了内脏运动反应，以至于对30 mmHg扩张的反应大于炎症前80 mmHg扩张所产生的反应。背柱损伤在对照条件下不影响内脏运动反射反应，但将结肠炎症后增加的反应降低至对照水平，并在炎症前进行时阻止了结肠炎症对反射反应的增强作用。我们的结果表明，在可能出现内脏痛觉过敏和痛觉超敏症状的炎症条件下，背柱通路在内脏痛传递中的作用会增强。腹外侧损伤消除了内脏运动反射，推测是通过中断一条涉及脑干的易化通路实现的。
