Wang Gexin, Tang Bin, Traub Richard J
Department of Biomedical Sciences, Dental School, University of Maryland, Baltimore, 21201, USA.
J Neurophysiol. 2005 Dec;94(6):3788-94. doi: 10.1152/jn.00230.2005. Epub 2005 Aug 10.
Previous studies suggest the lumbosacral (LS) spinal cord processes acute colorectal stimuli whereas the thoracolumbar (TL) and LS spinal segments process inflammatory stimuli. In this study, the effects of colorectal distention (CRD) on TL and LS dorsal horn neuronal activity were recorded in Nembutal-anesthetized male rats both with and without colonic inflammation. Both single cells (before and after inflammation) and populations (multiple cells from noninflamed or inflamed rats) were studied. CRD-responsive neurons had excitatory Abrupt (on-off with stimulus) or Sustained (prolonged after discharge) responses or were Inhibited by CRD. In noninflamed rats, a significantly greater percentage of LS neurons (63% Abrupt, 27% Sustained) were excited by CRD than TL neurons (61% Abrupt, 3% Sustained). The remaining cells were Inhibited (10% LS, 36% TL). LS Abrupt neurons had lower thresholds and greater response magnitudes to CRD compared with TL Abrupt neurons. After colonic inflammation, TL neurons became more excitable: the percentage of Inhibited neurons decreased, the response magnitude of Abrupt neurons increased, and the threshold decreased. In contrast, in single-cell recordings, the response of LS Sustained neurons increased, whereas LS Abrupt neurons decreased. These data suggest that in noninflamed rats, the net response to CRD of TL visceroceptive spinal sensory neurons is less than that of LS neurons. Colonic inflammation increases the net response of TL neurons and differentially modulates the response of LS neurons. These differences may contribute to the functional dichotomy between the TL and LS spinal segments in processing acute and inflammatory colorectal pain.
先前的研究表明，腰骶部（LS）脊髓处理急性结直肠刺激，而胸腰段（TL）和腰骶段脊髓节段处理炎症刺激。在本研究中，在戊巴比妥麻醉的雄性大鼠中，记录了有无结肠炎症时结直肠扩张（CRD）对胸腰段和腰骶段背角神经元活动的影响。研究了单细胞（炎症前后）和细胞群（来自未发炎或发炎大鼠的多个细胞）。对CRD有反应的神经元具有兴奋性突发（刺激时开启-关闭）或持续（放电后延长）反应，或被CRD抑制。在未发炎的大鼠中，被CRD兴奋的腰骶段神经元百分比（63%突发，27%持续）显著高于胸腰段神经元（61%突发，3%持续）。其余细胞被抑制（10%腰骶段，36%胸腰段）。与胸腰段突发神经元相比，腰骶段突发神经元对CRD的阈值更低，反应幅度更大。结肠炎症后，胸腰段神经元变得更易兴奋：被抑制神经元的百分比降低，突发神经元的反应幅度增加，阈值降低。相比之下，在单细胞记录中，腰骶段持续神经元的反应增加，而腰骶段突发神经元的反应减少。这些数据表明，在未发炎的大鼠中，胸腰段内脏感觉脊髓感觉神经元对CRD的净反应小于腰骶段神经元。结肠炎症增加了胸腰段神经元的净反应，并差异性地调节了腰骶段神经元的反应。这些差异可能有助于胸腰段和腰骶段脊髓节段在处理急性和炎症性结直肠疼痛时的功能二分法。
