Khan A M, Stanley B G, Bozzetti L, Chin C, Stivers C, Currás-Collazo M C
Department of Cell Biology and Neuroscience, University of California, Riverside, California 92521, USA.
J Comp Neurol. 2000 Dec 18;428(3):428-49.
Glutamate (Glu), a major excitatory neurotransmitter within the hypothalamus and thalamus, acts upon many receptors, including the N-methyl-D-aspartate (NMDA) subtype. Abundant evidence suggests that variations in the subunit composition of NMDA receptors (NMDA-Rs) contribute to differences in Glu's immediate electrophysiological effects as well as to the patterns of signal transduction cascades it triggers to mediate long-term changes in neuronal function. We have previously shown that hypothalamic NMDA-Rs containing the NR2B subunit may be involved in the control of eating as well as in the mediation of physiological responses to osmotic stimuli. To broaden our understanding of diencephalic NMDA-R participation in other functions, we localized the NR2B subunit in the diencephalon of the adult male rat using immunoperoxidase, immunogold, and immunofluorescence techniques and an affinity-purified polyclonal antibody specific for the NR2B subunit of the NMDA-R. In addition, we used a monoclonal NR2B antibody with immunoperoxidase detection to confirm the NR2B distribution seen with the polyclonal antibody. In the hypothalamus, the highest levels of NR2B immunoreactivity (-ir) were found in the magnocellular neurosecretory system, including the paraventricular and supraoptic nuclei. A new finding was that intense NR2B-ir was present within perivascular "accessory" magnocellular groups of this system, including the nucleus circularis, anterior fornical nucleus, and scattered clusters of lateral hypothalamic cells apposed to blood vessels. Robust NR2B-ir was also present within the arcuate nucleus, the median eminence, and the tuberal nucleus, and light immunostaining was found in all other hypothalamic nuclei examined. In the thalamus, the highest NR2B-ir was observed in the medial habenula and the anterodorsal, paraventricular, rhomboid, reticular, and dorsal lateral geniculate nuclei. As in the hypothalamus, all thalamic nuclei examined displayed at least light immunostaining for this subunit. Control sections, including those incubated with the polyclonal NR2B antibody preadsorbed with its fusion protein, were virtually devoid of immunostaining. This demonstration that the NR2B subunit of the NMDA-R is widely distributed in the diencephalon, implicates it in a wide variety of functions, and provides a useful anatomical framework for establishing a comprehensive map of Glu receptor populations within this major subdivision of the brain.
谷氨酸（Glu）是下丘脑和丘脑内主要的兴奋性神经递质，作用于许多受体，包括N-甲基-D-天冬氨酸（NMDA）亚型。大量证据表明，NMDA受体（NMDA-Rs）亚基组成的变化导致了Glu直接电生理效应的差异，以及它触发的信号转导级联反应模式，从而介导神经元功能的长期变化。我们之前已经表明，含有NR2B亚基的下丘脑NMDA-Rs可能参与进食控制以及对渗透刺激的生理反应调节。为了更深入了解间脑NMDA-R在其他功能中的作用，我们使用免疫过氧化物酶、免疫金和免疫荧光技术以及针对NMDA-R的NR2B亚基的亲和纯化多克隆抗体，在成年雄性大鼠的间脑中定位NR2B亚基。此外，我们使用带有免疫过氧化物酶检测的单克隆NR2B抗体来确认多克隆抗体所显示的NR2B分布。在下丘脑中，NR2B免疫反应性（-ir）水平最高的区域是大细胞神经分泌系统，包括室旁核和视上核。一个新发现是在该系统的血管周围“附属”大细胞群中存在强烈的NR2B-ir，包括环状核、穹窿前核以及与血管相邻的下丘脑外侧细胞散在簇。在弓状核、正中隆起和结节核中也存在较强的NR2B-ir，在所有其他检查的下丘脑核团中发现轻度免疫染色。在丘脑中，在内侧缰核以及前背核、室旁核、菱形核、网状核和背外侧膝状核中观察到最高的NR2B-ir。与下丘脑一样，所有检查的丘脑核团对该亚基至少显示轻度免疫染色。对照切片，包括用与其融合蛋白预吸附的多克隆NR2B抗体孵育的切片，几乎没有免疫染色。NMDA-R的NR2B亚基在间脑中广泛分布的这一证明，表明它参与多种功能，并为在大脑的这一主要分区内建立Glu受体群体的综合图谱提供了有用的解剖学框架。
