Milner T A, Pickel V M
J Comp Neurol. 1986 May 15;247(3):326-43. doi: 10.1002/cne.902470304.
We sought to determine (1) the ultrastructural localization and (2) the extrinsic sources of neurotensin-like immunoreactivity (NTLI) in the parabrachial region (PBR). The brains from untreated adult male rats and from others that received intraventricular injections of colchicine (100 micrograms/7.5 microliters saline) 24 hours prior to death were fixed by perfusion with acrolein or glutaraldehyde and paraformaldehyde. Coronal sections were immunocytochemically labeled with a polyclonal rabbit antiserum to neurotensin and the PAP method. Western dot-blots and immunocytochemical labeling with adsorbed antiserum revealed significant cross-reaction only against NT, NT8-13, and glutamine (Gln)4-NT. In the ultrastructural study, the most numerous labeled profiles were axons and axon terminals in both colchicine-treated and control animals. The terminals containing NTLI were characterized by a mixed population of small, clear and large, dense core vesicles; asymmetric junctions principally with unlabeled dendrites; and a few synaptic specializations with unlabeled axon terminals. Compared to axon terminals, relatively few perikarya or dendrites had detectable levels of NTLI in either untreated or colchicine-treated animals. The labeled perikarya measured 8-10 microns in longest cross-sectional diameter, contained NTLI throughout a narrow rim of cytoplasm, and received a few somatic synapses from unlabeled terminals. From the relative density of axon terminals and sparsity of perikarya and dendrites, we conclude that the NTLI in the PBR is principally derived from extrinsic neurons. However, the intrinsic neurons with NTLI may also contribute to the immunoreactivity in the axon terminals of the PBR. We sought to determine the precise location of the extrinsic neurons that contribute to the NTLI in axon terminals in the PBR. Following unilateral injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), dual labeling was most evident in a large population of neurons located in the dorsal, medial and commissural nuclei of the solitary tracts, ipsilateral to the side of the injection. However, a few perikarya containing both the retrogradely transported WGA-HRP and immunocytochemical labels for NT were also detected in the caudal ventrolateral reticular formation, the locus coeruleus, and the paraventricular and lateral hypothalamic nuclei. We conclude that (1) NT or a closely related peptide is present in intrinsic neurons and multiple afferent pathways to the PBR; and (2) the axon terminals with NTLI have synaptic interactions with dendrites of intrinsic neurons and with axon terminals that may have either extrinsic or intrinsic origins.
(1) 臂旁区（PBR）中神经降压素样免疫反应性物质（NTLI）的超微结构定位；(2) 其外源性来源。对未处理的成年雄性大鼠以及在处死前24小时接受脑室内注射秋水仙碱（100微克/7.5微升生理盐水）的大鼠的大脑，用丙烯醛或戊二醛与多聚甲醛进行灌注固定。冠状切片用抗神经降压素的兔多克隆抗血清和PAP法进行免疫细胞化学标记。蛋白质免疫印迹法和用吸附抗血清进行的免疫细胞化学标记显示，仅与神经降压素、NT8 - 13和谷氨酰胺（Gln）4 - NT有显著交叉反应。在超微结构研究中，在秋水仙碱处理组和对照组动物中，标记最多的结构是轴突和轴突终末。含有NTLI的终末的特征是有小而清亮的囊泡和大而致密核心囊泡的混合群体；主要与未标记的树突形成不对称突触；以及少数与未标记轴突终末形成的突触特化结构。与轴突终末相比，在未处理或秋水仙碱处理的动物中，相对较少的胞体或树突有可检测到的NTLI水平。标记的胞体最长横径为8 - 10微米，在狭窄的细胞质边缘含有NTLI，并从未标记的终末接受少数体突触。根据轴突终末的相对密度以及胞体和树突的稀疏程度，我们得出结论，PBR中的NTLI主要来源于外源性神经元。然而，具有NTLI的内在神经元也可能对PBR轴突终末的免疫反应性有贡献。我们试图确定对PBR轴突终末中NTLI有贡献的外源性神经元的精确位置。在单侧注射小麦胚凝集素结合辣根过氧化物酶（WGA - HRP）后，双重标记在注射侧同侧位于孤束核的背侧、内侧和连合核的大量神经元中最为明显。然而，在尾侧腹外侧网状结构、蓝斑以及室旁核和下丘脑外侧核中也检测到少数同时含有逆行转运的WGA - HRP和NT免疫细胞化学标记的胞体。我们得出结论：(1) 神经降压素或一种密切相关的肽存在于内在神经元以及至PBR的多条传入通路中；(2) 含有NTLI的轴突终末与内在神经元的树突以及可能具有外源性或内源性起源的轴突终末有突触相互作用。
