Sun N, Yi H, Cassell M D
Department of Anatomy, University of Iowa, Iowa City 52242.
J Comp Neurol. 1994 Feb 1;340(1):43-64. doi: 10.1002/cne.903400105.
The synaptic circuitry of the intrinsic GABAergic system of the central extended amygdala (CEA) in relation to efferent neurons and cortical afferents was examined in the present study. Neurons in the CEA projecting to the dorsal vagal complex and the parabrachial complex were identified by the retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). Postembedding GABA-immunocytochemistry revealed that GABA-immunoreactive (GABA-IR) terminals formed largely symmetrical synaptic contacts with the perikarya and proximal dendritic processes of almost all WGA-HRP-labeled neurons in the CEA. To determine the relationship between cortical afferents and CEA GABAergic neurons, WGA-HRP was used to anterogradely label afferents from the insular cortex in combination with postembedding immunogold detection of GABA. Cortical afferents formed asymmetrical synaptic contacts predominantly on small dendrites and dendritic spines. Many of the dendrites postsynaptic to cortical terminals in the central nucleus were immunoreactive for GABA although only relatively few spines were GABA-IR. Combining pre-embedding GAD-immunocytochemistry with cortical lesions resulted in approximately 40% of degenerating terminals of insular cortical origin in the central nucleus in contact with small, GAD-IR dendrites and spines. The present results demonstrate that the neurons providing the major CEA outputs to the brainstem receive an extensive GABAergic innervation, strongly supporting our proposal that CEA efferent neurons are under strong tonic inhibition by intrinsic GABAergic neurons. Further, our finding that the major cortical input to the central nucleus preferentially innervates intrinsic GABAergic neurons suggests that these neurons in the CEA may serve as an interface between the principal inputs and outputs of this forebrain region.
在本研究中，我们检查了中央扩展杏仁核（CEA）内在GABA能系统与传出神经元和皮质传入神经相关的突触回路。通过小麦胚芽凝集素 - 辣根过氧化物酶（WGA - HRP）的逆行运输来识别CEA中投射到迷走神经背侧复合体和臂旁复合体的神经元。包埋后GABA免疫细胞化学显示，GABA免疫反应性（GABA - IR）终末与CEA中几乎所有WGA - HRP标记神经元的胞体和近端树突过程形成大量对称的突触联系。为了确定皮质传入神经与CEA GABA能神经元之间的关系，将WGA - HRP用于顺行标记来自岛叶皮质的传入神经，并结合包埋后GABA的免疫金检测。皮质传入神经主要在小的树突和树突棘上形成不对称的突触联系。中央核中皮质终末的许多突触后树突对GABA有免疫反应，尽管只有相对较少的树突棘是GABA - IR。将包埋前GAD免疫细胞化学与皮质损伤相结合，导致中央核中约40%的岛叶皮质起源的退化终末与小的、GAD - IR树突和树突棘接触。目前的结果表明，向脑干提供主要CEA输出的神经元接受广泛的GABA能神经支配，有力地支持了我们的提议，即CEA传出神经元受到内在GABA能神经元的强烈紧张性抑制。此外，我们发现中央核的主要皮质输入优先支配内在GABA能神经元，这表明CEA中的这些神经元可能作为该前脑区域主要输入和输出之间的界面。
