FUNCTION OF DESCENDING CONTROL AND NEUROACTIVE SUBSTANCE RECEPTORS IN OROFACIAL PAIN

NK-1受体拮抗剂可抑制C纤维传入脊髓伤害性神经元引起的迟发性放电，提示P物质在急性疼痛中的作用。然而，该拮抗剂未能在大多数脊髓丘脑神经元中抑制它们。本实验旨在探讨NK-1受体在经中缝大核(NRM)下行抑制脊髓中间神经元中的作用。在戊巴比妥钠麻醉(50 mg/kg)和潘可溴铵固定的条件下，对Wistar大鼠腰背角I层伤害性特异性神经元和宽动态范围神经元进行单位记录。测试投射到C_3或更高水平的大脑，以及电刺激感受场和NRM电刺激(20个脉冲，0.2ms，40 Hz)所诱发的迟发放电(100-400ms)。生理鉴定后，将18-37nmoR-67580(大鼠NK-1受体拮抗剂)涂于脊髓表面，10-20min后冲洗干净。每隔10~15min计数一次C-放电，持续60~90min，记录63个神经元，分析43个中间神经元。拮抗剂的最大抑制幅度与刺激NRM之间存在显著的相关性(相关系数为0.73)。

NK-1 receptor antagonist inhibited the late discharges evoked by C-fiber input in the spinal nociceptive neurons, suggesting the role of substance P in acute pain. The antagonist, however, failed to inhibit them in the majority of spinothalamic neurons. This experiment was aimed to investigate the role of NK-1 receptor in the spinal interneurons during the descending inhibition via the nucleus raphe magnus (NRM).Under pentobarbital sodium anesthesia (50 mg/kg) and immobilization with pancronium bromide, single unit recordings were made from the nociceptive specific or wide dynamic range neurons in the lamina I of lumber dorsal horn of Wistar rats. They were tested for projections to C_3 or higher levels of brain and the late discharges (100-400 ms) evoked by electrical stimulations of the receptive fields and the effects of NRM electrical stimulations (a train of 20 pulses, 0.2 ms duration, 40 Hz). After physiological characterization, a dose of 18-37 nmol of RP-67580 (rat NK-1 receptor antagonist) was applied onto the cord surface and washed out after 10-20 min. The C-discharges were counted every 10-15 min for 60-90 min.Sixty three neurons were recorded and 43 interneurons were analyzed. A significant relationship was found between the magnitudes of maximum inhibitions by the antagonist and NRM stimulation (correlation 0.73).