大鼠中缝大核向脊髓投射神经元与神经降压素能终末的突触联系

Synaptic connections between neurotensinergic terminals and neurons in the nucleus raphe magnus projected to the spinal dorsal horn in the rat

神经降压素(NT)是中枢下行抑制系统的重要神经活性物质。本研究运用免疫组织化学与逆行追踪法相结合的双标技术,在电镜下观察NT能终末与中缝大核(NRM)向脊髓投射神经元的突触联系。在光镜下可见NT阳性纤维和终末散在分布于NRM,但未见NT阳性神经元;将HRP注入腰髓背角后,在NRM内可见比较密集的HRP逆标神经元。在电镜下可见NT阳性终末与HRP逆标神经元的胞体和树突形成以非对称性为主的轴-体突触和轴-树突触。上述结果说明NT可能调控NRM向脊髓背角投射神经元的活动,借此对伤害性信息向中枢的传递发挥抑制效应。

Neumtensin （NT） is an important neuroactive substance for the central descending pain control system. In the present study, employing immunohistochemical staining combined with retrograde tracing, we investigated the synaptic connections between neurotensinergic terminals and neurons in the nucleus raphe magnus （NRM） which projected to the spinal dorsal horn in the rat. Under the light microscope, after immunohistochemical staining for NT and injecting horseradish perexidase （HRP） into the lumbar spinal dorsal horn, scattered NT immunoreactive fibers and terminals and HRP retrogradcly labeled neurons were observed in the NRM, respectively. But NT immunoreactive neuronal cell bodies were not encountered. Under the electron microscope, both symmetric and asymmetric axon-sematic and axon-dendritic synapses made by NT-immunoreactive terminals and HRP retrogradely labeled neuronal cell bodies and dendritic processes were observed, but the majority of them were asymmetric axon-dendritic synapses. The present results suggest that NT might exert its inhibitory effects for transmission of the noxious information from peripheral to the central nervous system through activating the activities of the neurons in the NRM which send projection fibers to the spinal dorsal hom.