Function of Receptors of neuroactive Substances in the ascending neurons conveying oro-facial, visceral and derma pain

在戊巴比妥钠麻醉下，观察脊髓局部应用新型啮齿动物特异性NK-1受体拮抗剂RP-67580对大鼠脊髓背角浅层脊髓丘脑和非投射神经元电诱发迟发性放电的影响。他们被测试丘脑和颈髓(C3)的投射，以及电刺激感受野所引起的迟发放电。将0.4-37nmol的RP-67580直接涂抹在记录部位附近的脊髓表面。每隔10~30min检查一次药效，持续30~180min。应用RP-67580抑制大多数非投射神经元的放电率。另一方面，大多数脊髓丘脑神经元的反应不受影响，甚至增强。该拮抗剂的最大抑制幅度与刺激中缝大核之间存在显著的相关性(相关系数为0.73)。本研究表明，RP-67580选择性地抑制非投射神经元的C-诱发放电。结果提示，SP在脊髓丘脑和非投射神经元中的作用不同，在正常急性疼痛的初级传入C纤维介导的伤害性传递或调制中起重要作用。本研究还表明，刺激NRM可抑制NK-1受体介导的伤害性反应。

The effects of local spinal application of new, specific NK-1 receptor antagonist for rodents, RP-67580 on the electrically-evoked late discharges of spinothalamic and non-projection neurons in the rat superficial spinal dorsal horn were examined.Under pentobarbital sodium anesthesia, single-unit recordings were made from the nociceptive neurons in lamina I of the lumber spinal cord. They were tested for the projections to thalamus and cervical cord (C3) and for the late discharges evoked by electrical stimulation of the receptive fields. Doses of 0.4-37 nmol of RP-67580 were applied directly onto the cord surface close to the recording site. Drug effects were examined every 10-30 min for 30-180 min. they also were tested for the effects of NRM electrical stimulations (a train of 20 pulses, 0.2 ms duration, 40Hz).The rate discharges of majority of non-projection neurons were inhibited by the application of RP-67580. On the other hand, the responses of the majority of spinothalamic neurons were not affected or rather increased. A significant relationship was found between the magnitudes of maximum inhibitions by the antagonist and NRM stimulation (correlation 0.73).This study demonstrated that RP-67580 inhibited the C-evoked discharges of the nonprojection neurons selectively. The results suggest that the role of SP was different between the spinothalamic and non-projection neurons, and that SP plays an important role in nociceptive transmission or modulation mediated by primary afferent C-fibers mainly in the interneurons in normal acute pain. This study also demonstrated that the nociceptive responses mediated by NK-1 receptor are inhibited by NRM stimulation.