The dorsal column pathway consists of direct projections from primary afferents and of ascending fibers of the post-synaptic dorsal column (PSDC) cells. This pathway mediates touch but may also mediate allodynia after nerve injury. The role of PSDC neurons in nerve injury-induced mechanical allodynia is unknown. Repetitive gentle, tactile stimulus or noxious pinch was applied to the ipsilateral hindpaw of rats with spinal nerve ligation (SNL) or sham surgery that had previously received tetramethylrhodamine dextran in the ipsilateral n. gracilis. Both touch and noxious stimuli produced marked increases in FOS expression in other cells throughout all laminae of the ipsilateral dorsal horn after nerve injury. However, virtually none of the identified PSDC cells expressed FOS immunofluorescence in response to repetitive touch or pinch in either the nerve-injured or sham groups. In contrast, labeled PSDC cells expressed FOS in response to ureter ligation and labeled spinothalamic tract (STT) cells expressed FOS in response to noxious pinch. Identified PSDC neurons from either sham-operated or SNL rats did not express immunoreactivity to substance P, CGRP, NPY, PKCY, MOR, the NK1 and the NPY-Y1 receptor. Retrogradely labeled DRG cells of nerve injured rats were large diameter neurons, which expressed NPY, but no detectable CGRP or substance P. Spinal nerve injury sensitizes neurons in the spinal dorsal horn to repetitive light touch but PSDC neurons apparently do not participate in touch-evoked allodynia. Sensitization of these non-PSDC neurons may result in activation of projections integral to the spinal/supraspinal processing of enhanced pain states and of descending facilitation, thus priming the central nervous system to interpret tactile stimuli as being aversive.

译文

背柱途径由初级传入的直接投射和突触后背柱 (PSDC) 细胞的上升纤维组成。该途径介导触摸,但也可能介导神经损伤后的异常性疼痛。PSDC神经元在神经损伤引起的机械性异常性疼痛中的作用尚不清楚。重复的轻柔,触觉刺激或有害的捏合作用被应用于患有脊神经结扎 (SNL) 或假手术的大鼠的同侧后爪,这些大鼠先前在同侧gracilis中接受了四甲基罗丹明葡聚糖。神经损伤后,在同侧背角的所有层中,触摸和有害刺激均使其他细胞中的FOS表达显着增加。然而,在神经损伤或假手术组中,几乎没有鉴定出的PSDC细胞响应于重复触摸或捏合而表达FOS免疫荧光。相反,标记的PSDC细胞响应输尿管结扎表达FOS,而标记的脊髓丘脑束 (STT) 细胞响应有害的挤压表达FOS。鉴定出的来自假手术或SNL大鼠的PSDC神经元对p物质,CGRP,NPY,PKCY,MOR,NK1和NPY-Y1受体不表达免疫反应性。神经损伤大鼠逆行标记的DRG细胞为大直径神经元,表达NPY,但未检测到CGRP或p物质。脊神经损伤使脊髓背角的神经元对重复的轻触敏感,但PSDC神经元显然不参与触摸诱发的异常性疼痛。这些非PSDC神经元的敏化可能导致增强的疼痛状态和下降的促进作用的脊髓/脊髓上处理的投影的激活,从而引发中枢神经系统将触觉刺激解释为令人厌恶的。

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