Barnes K L, McQueeney A J, Barrett W R, Knowles W D
Department of Neurosciences, Cleveland Clinic Foundation, OH 44195-5286.
Brain Res Bull. 1994;34(4):339-48. doi: 10.1016/0361-9230(94)90027-2.
The suitability of the anterograde tracer neurobiotin to provide information about the morphology and projections of extracellularly or intracellularly recorded medial nucleus tractus solitarii (nTS) neurons was evaluated in horizontally oriented rat dorsal medulla in vitro slices. After responsiveness to angiotensin (Ang) II, substance P (SP), and L-glutamate was evaluated, neurons were labeled by electrophoresis of neurobiotin at the recording site. Extracellular application (2 microA for 2 min) produced discrete injection sites (40-70 microns) with a small group of labeled neurons. Ejections into the solitary tract documented that the tracer was not taken up by axons traversing the injection site. Neuronal perikarya, primary and secondary dendrites, and axons exhibited a dense Golgi-like appearance, with well-defined dendritic spines and axonal varicosities. Dendritic or axonal processes could be followed for more than 1 mm from the cell soma in a 50 microns thick section, documenting the horizontal architecture of the medial nTS. Intracellular electrophoresis filled the soma, primary and secondary dendrites, and axons of neurons characterized for responsiveness to peptides, L-glutamate and solitary tract stimulation. The location within the nTS and axonal projections of neurons responsive to Ang II and SP appeared to differ from those of cells responsive to Ang II and L-glutamate. Thus, either extracellular or intracellular application of neurobiotin in the in vitro slice can reveal differences in axonal or dendritic targets of neuronal subgroups responsive to different neurotransmitters or peptides and provide evidence for the likely autonomic significance of the neurons.
在体外水平取向的大鼠延髓背侧切片中，评估了顺行示踪剂神经生物素用于提供有关细胞外或细胞内记录的孤束核内侧核（nTS）神经元形态和投射信息的适用性。在评估对血管紧张素（Ang）II、P物质（SP）和L-谷氨酸的反应性之后，通过在记录部位对神经生物素进行电泳来标记神经元。细胞外施加（2微安，持续2分钟）产生离散的注射部位（40 - 70微米），有一小群标记神经元。向孤束内注射证明示踪剂不会被穿过注射部位的轴突摄取。神经元胞体、一级和二级树突以及轴突呈现出密集的高尔基样外观，具有明确的树突棘和轴突膨体。在50微米厚的切片中，树突或轴突过程可从细胞体追踪超过1毫米，记录了内侧nTS的水平结构。细胞内电泳填充了对肽、L-谷氨酸和孤束刺激有反应的神经元的胞体、一级和二级树突以及轴突。对Ang II和SP有反应的神经元在nTS内的位置和轴突投射似乎与对Ang II和L-谷氨酸有反应的细胞不同。因此，在体外切片中细胞外或细胞内应用神经生物素可以揭示对不同神经递质或肽有反应的神经元亚群在轴突或树突靶点上的差异，并为这些神经元可能的自主神经意义提供证据。
