The abnormality of the descending inhibitory system in the brain stem by the peripheral axotomy and neuropathic pain

已知外周组织、内脏器官、皮肤等的伤害性信息由具有A δ和C纤维的初级感觉神经元通过脊髓背角传递到中枢。 这些信息也被认为是由脑干中的肾上腺素能和去甲肾上腺素能神经元根据情况负调节的。 在我们的研究中，背角深层的许多神经元被伤害性感受器中的神经调节剂P物质兴奋。 这一结果意味着这些神经元参与痛觉的传递或调制。 此外，令人惊讶的是，其中一些被认为是兴奋性的，但不是抑制性的，由肾上腺素能和去甲肾上腺素能神经元调节。 虽然从我们目前的研究结果推断的神经机制的生理作用是未知的，以前的下行抑制系统将不得不重新考虑。

It is known that the noxious information in the peripheral tissues, the visceral organs, the skin and others, is carried by the primary sensory neurons with A delta and C fibers to the central nervous system via spinal dorsal horn. The information is thought to be also negatively regulated by the serotonergic and the noradrenergic neurons in the brain stem according to the situation. In our study, many neurons in the deep lamina of dorsal horn were excited by substance P, which is the neuromodulator in the nociceptors. This result mean the these neurons are involved in the transmission or modulation of pain sensation. Moreover, surprisingly, some of these are suggested to be excitatory, but not inhibitory, regulated by serotonergic and noradrenergic neurons. Although the physiological roles for the neural mechanism inferred from our present findings is unknown, the previous descending inhibitory system will have to be be reconsidered.