Role of Inhibitory Cortical Interneurons in the Neural Circuit between the Prefrontal Cortex and the Mediodorsal Nucleus of the Thalamus

前额叶皮层和丘脑背内侧核之间的神经回路已被充分研究，并以地形学的方式相互连接。然而，还没有详细研究抑制性皮层中间神经元如何参与神经回路。为了解决这个问题，我们对大鼠大脑进行了三项联合神经解剖学研究。首先，它已被确定的频率和空间分布的突触重建树突的非锥体神经元确定浸渍与高尔基体的方法和丘脑皮质终端确定退化。退化终端从MD被发现，使直接的突触接触，无论是小尺寸的树突轴或棘高尔基浸渍非锥体细胞非常稀疏的树突棘。第二，用GABA免疫细胞化学方法研究了菜豆白细胞凝集素（PHA-L）的顺行转运 ...更多信息 实验结果表明，来自MD的PHA-L标记的终末与用免疫金颗粒标记的树突轴和棘形成突触连接，指示GABA免疫反应性。有趣的是，未标记的树突棘被发现接受来自具有PHA-L标记的MD和具有免疫金颗粒的GABA能细胞的轴突输入。此外，在树突轴和轴突终末之间发现了突触，两者均被免疫金颗粒标记。第三，用麦胚凝集素结合辣根过氧化物酶（WGA-HRP）和埋藏后GABA免疫细胞化学方法研究了皮质丘脑向MD投射的神经元与GABA能终末之间的突触联系。边缘前皮质GABA能终末与逆行标记的皮质丘脑神经元形成突触联系。这些结果首次证实了边缘前皮层不仅存在MD的丘脑皮质终末与GABA能中间神经元之间的突触联系，而且存在MD的GABA能终末与皮质丘脑神经元之间的突触联系。结果表明，GABA能中间神经元对MD和前额叶皮层之间的兴奋性回响具有调节作用。少

The neural circuit between the prefrontal cortex and the mediodorsal nucleus of the thalamus (MD) is well investigated and known to be reciprocally interconnected in a topographical manner. However, it has not been investigated in detail how inhibitory cortical interneurons are involved in the neural circuit. To address this issue, we conducted three combined neuroanatomical studies on the rat brain. First, it has been determined that the frequency and the spatial distribution of synapses made by reconstructed dendrites of nonpyramidal neurons identified by impregnation with the Golgi method and thalamocortical terminals identified by degeneration. Degenerating terminals from MD were found to make direct synaptic contacts with either small-sized dendritic shafts or spines of Golgi-impregnated nonpyramidal cells with very sparse dendritic spines. Secondly, a combined study of the anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L) and postembedding GABA immunocytochemist … More ry resulted I that PHA-L-labeled terminals from MD made synaptic junctions with dendritic shafts and spines labeled with immunogold particles indicative of GABA immunoreactivity. Interestingly, non-labeled dendritic spines were found to receive both axonal inputs from MD with PHA-L labelings and from GABAergic cells with immunogold particles. In addition, there found synapses between dendritic shafts and axon terminals, both of which were labeled with immunogold particles. Thirdly, synaptic connections between corticothalamic neurons projecting to MD and GABAergic terminals were investigated using wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) and postembedding GABA immunocytochemistry. GABAergic terminals in the prelimbic cortex made synaptic contacts with retrogradely labeled corticothalamic neurons to MD. All of the synapses were found on cell somata and thick dendritic trunks.These results provide the first demonstration of synaptic contacts in the prelimbic cortex not only between thalammocortical terminals from MD and GABAergic interneurons but also between GABAergic terminals and corticothalamic neurons to MD. The anatomical findings suggest that GABAergic interneurons have a modulatory influence on the excitatory reverberation between MD and the prefrontal cortex. Less