弓状核内神经紧张素能神经元与神经肤Y能神经元关系的免疫电镜双标记研究

THE RELATIONSHIP BETWEEN NT- AND NPY-NEURONS IN THE ARCUATE NUCLEUS A DOUBLE LABELING IMMUNOELECTRON MICROSCOPIC STUDY

用包埋前免疫电镜PAP双标记技术,对大鼠下丘脑弓状核内的神经紧张素(NT)和神经肽Y(NPY)的分布进行了超微结构研究。先用DAB法显示NPY免疫反应。然后用钼酸铵-TMB法显示NT免疫反应,再经DAB-氯化钴稳定后作免疫电镜包埋。结果:在弓状核内,NPY免疫反应产物呈电子密度高的颗粒状或絮状沉淀,弥漫分布于核周质的细胞器和基质、树突的微管周围、轴突的小透亮囊泡周围。NT免疫反应产物则为致密的针状或块状,散在分布于核周质、树突和轴突内。两者极易分辨。NPY能和NT能神经结构在弓状核内呈交错分布,彼此关系密切。含NPY的树突和轴突与免疫反应阴性轴突形成突触连接;含NT的胞体和树突与免疫反应阴性轴突形成突触连接。此外,NPY阳性轴突末梢还与NT阳性树突形成对称性轴-树突触。本研究结果为下丘脑NT能神经元的肽能突触调节提供了又一新的超微结构依据。

The distribution of neurotensin (NT) and neuropeptide Y (NPY) in the rat hypothalamic arcuate nucleus has been studied ultrastructurally by means of double labeling preembedding immunoelectron microscopic PAP technique. First, the NPY immunoreaction was demonstrated by chromogen DAB, and second, the NT immunoreaction was demonstrated by ammonium molybdate-TMB method. After being stabilized by DAB-cobalt chloride, the vibratome sections were processed for electron microscopic study. The results showed that in the arcuate nucleus the NPY immunoreactive products appeared as high electron-dense granular or flocculent materials deposited diffusely in the organelles and matrix of perikaryon, around the dendritic microtubules and axonic small clear vesicles. Whereas the NT immunoreactive products were dense needle- or mass-like deposits distributed dispersively in the perikaryon, dendrites and axon terminals. They can easily be distinguished although being intermingled together. The NPY-containing dendrites and axons formed synaptic connections with immuno-negative axon terminals, NT-containing somata and dendrites formed also synaptic conections with negative axon terminals. In addition, NPY-positive axon terminals formed symmetrical axodendritic synapses with NT-positive dendrites. The present results provided another new ultrastructural evidence for the peptidergic synaptic regulation of NT neurons in hypothalamus.