内脏痛与体表相关性的实验研究

Interactions between visceral nociception and tactile inputs

目的:研究大鼠丘脑腹后外侧核(VPL)单细胞中皮肤触觉与内脏伤害性传入的相互作用与规律性。方法:用球囊扩张直-结肠(CRD)的方法产生内脏痛刺激,10H_z气流喷射皮肤感受野产生触觉刺激。两种刺激先后给予以观察先行条件刺激对其后的检验刺激反应的影响。结果:在记录的70个对CRD和皮肤刺激都有确定反应的VPL神经元中,44％(31/70)的细胞对CRD反应在触觉条件刺激之后有所抑制,而54％(38/70)在CRD伤害性条件刺激之后触觉反应表现为增强。对CRD有反应的细胞的皮肤敏感点多数分布在下肢外侧,主要沿相当于中医经络理论中的胃经及胆经下段分布。结论:在丘脑单细胞水平,条件性皮肤触觉刺激可在一定程度上抑制内脏痛觉反应。相反,内脏伤害性刺激后可引起VPL神经元对皮肤触觉的过度反应,可能与内脏病变时临床常见的体表敏感点有关。

AIM: To study the interactions between skin tactile and visceral nociceptive inputs in the ventroposterior lateral (VPL) nucleus of the rat thalamus. METHODS: Visceral nociceptive inputs were generated by colorectal distension (CRD). Skin tactile inputs were generated by 10 Hz skin puff. They were delivered in sequence to investigate the changes in reaction to the test stimulus after the conditioning stimulation. RESULTS: Among the isolated 78 single VPL neurons that had response to both CRD and skin tactile stimuli, 44% (31/70) had their response to CRD reduced by the preceding conditioning tactile stimulation, and 54% (38/70) had their tactile response enhanced by the preceding CRD. The skin receptive fields of the majority of the cells were located along the caudal part of the Meridians of Stomach and Gallbladder of Chinese medicine. CONCLUSIONS: (1) Conditioning tactile inputs may inhibit noxious colorectal inputs, but this effect was short-lasting and limited at single neuron level. (2) On the other hand, pre-existing visceral nociception may cause abnormally high discharge of thalamic neurons, a phenomenon that may be related to the clinically seen allodynia on the body surface in visceral lesions.