Department of Biology, Neurosciences Institute, University of Texas at San Antonio, Biosciences Building 1.03.26, One UTSA Circle, San Antonio, TX 78249, USA.
Cereb Cortex. 2018 Apr 1;28(4):1154-1167. doi: 10.1093/cercor/bhx025.
Anatomical studies have shown that the majority of callosal axons are glutamatergic. However, a small proportion of callosal axons are also immunoreactive for glutamic acid decarboxylase, an enzyme required for gamma-aminobutyric acid (GABA) synthesis and a specific marker for GABAergic neurons. Here, we test the hypothesis that corticocortical parvalbumin-expressing (CC-Parv) neurons connect the two hemispheres of multiple cortical areas, project through the corpus callosum, and are a functional part of the local cortical circuit. Our investigation of this hypothesis takes advantage of viral tracing and optogenetics to determine the anatomical and electrophysiological properties of CC-Parv neurons of the mouse auditory, visual, and motor cortices. We found a direct inhibitory pathway made up of parvalbumin-expressing (Parv) neurons which connects corresponding cortical areas (CC-Parv neurons → contralateral cortex). Like other Parv cortical neurons, these neurons provide local inhibition onto nearby pyramidal neurons and receive thalamocortical input. These results demonstrate a previously unknown long-range inhibitory circuit arising from a genetically defined type of GABAergic neuron that is engaged in interhemispheric communication.
解剖学研究表明，大多数胼胝体轴突是谷氨酸能的。然而，一小部分胼胝体轴突也对谷氨酸脱羧酶呈免疫反应，谷氨酸脱羧酶是 GABA 合成所必需的酶，也是 GABA 能神经元的特定标志物。在这里，我们检验了这样一个假设，即皮层间表达小清蛋白的（CC-Parv）神经元连接大脑两个半球的多个皮质区域，通过胼胝体投射，并构成局部皮质回路的一个功能部分。我们利用病毒追踪和光遗传学来研究这一假设，以确定小鼠听觉、视觉和运动皮质的 CC-Parv 神经元的解剖和电生理特性。我们发现了一个由表达小清蛋白的（Parv）神经元组成的直接抑制通路，它连接着相应的皮质区域（CC-Parv 神经元→对侧皮质）。与其他 Parv 皮质神经元一样，这些神经元对附近的锥体神经元提供局部抑制，并接收丘脑皮质输入。这些结果表明，一种以前未知的长程抑制回路来自于一种遗传定义的 GABA 能神经元类型，它参与了半球间的通讯。
