Non-descending inputs to the sympathetic preganglionic neuron and their synaptic structures.

1)为了确定中间外侧核（IML）中的非下行神经末梢，在T6水平切断大鼠脊髓。术后7天，脊髓下段内侧髓内5-羟色胺（5-HT）阳性终末完全消失。然而，P物质，脑啡肽，酪氨酸羟化酶（TH）的免疫反应阳性神经末梢仍然存在于IML。电子显微镜观察显示，这些免疫反应阳性终末和IML神经元之间的突触接触的存在。这一结果表明，存在神经元的输入，从内在或脊髓下结构的神经元交感节前神经元。2）为了检查的TH免疫反应的非下行终末在IML的可能来源，逆行神经元示踪实验。将霍乱毒素B（CT B）注入T2-13节段脊髓后，位于胸交感神经节（T2-11）的节后细胞被CT B优先标记。提示胸交感神经节节后神经元向胸脊髓投射。

1) In order to determine non-descending nerve terminals in the intermediolateral nucleus (IML), rat spinal cord was transected at T6 level. Seven days after the operation, serotonin (5-HT)-immunoreactive terminals disappeared completely from the IML of lower spinal cord. However, substance P-, enkephalin-, and tyrosine hydroxylase (TH)-immunoreactive nerve terminals remained in the IML.Electron microscopic observations revealed presence of synaptic contacts between these immunoreactive terminals and IML neurons. This result indicates presence of neuronal inputs from neurons in intrinsic or sub-spinal structures to the sympathetic preganglionic neurons.2) To examine a possible origin of TH-immunoreactive non-descending terminals in the IML,retrograde neuronal tracing experiments were made. After injection of cholera toxin B (CTB) into the spinal cord of levels T2-13, postganglionic cells located in thoracic sympathetic ganglia (T2-11) were labeled preferentially with CTB.Injections into more rostral (C6) or caudal (L1, L5) spinal cord segments resulted in few labeled ganglion cells. This result suggest that postganglionic neurons in the thoracic sympathetic ganglion project to thoracic spinal cord.