McDonald A J, Mascagni F
Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, 6439 Garner's Ferry Road, VA Building 1, C-43, Columbia, SC 29208, USA.
Neuroscience. 2006;138(2):537-47. doi: 10.1016/j.neuroscience.2005.11.047. Epub 2006 Jan 18.
The expression of Kv3.1 and Kv3.2 voltage-gated potassium channel subunits appears to be critical for high-frequency firing of many neuronal populations. In the cortex these subunits are mainly associated with fast-firing GABAergic interneurons containing parvalbumin or somatostatin. Since the basolateral nuclear complex of the amygdala contains similar interneurons, it is of interest to determine if these potassium channel subunits are expressed in these same interneuronal subpopulations. To investigate this issue, peroxidase and dual-labeling fluorescence immunohistochemistry combined with confocal laser scanning microscopy was used to determine which interneuronal subpopulations in the basolateral nuclear complex of the rat amygdala express Kv3.1b and Kv3.2 subunits. Antibodies to parvalbumin, somatostatin, calretinin, and cholecystokinin were used to label separate subsets of basolateral amygdalar interneurons. Examination of immunoperoxidase preparations suggested that the expression of both channels was restricted to nonpyramidal interneurons in the basolateral amygdala. Somata and proximal dendrites were intensely-stained, and axon terminals arising from presumptive basket cells and chandelier cells were lightly stained. Immunofluorescence observations revealed that parvalbumin+ neurons were the main interneuronal subpopulation expressing the Kv3.1b potassium channel subunit in the basolateral amygdala. More than 92-96% of parvalbumin+ neurons were Kv3.1b+, depending on the nucleus. These parvalbumin+/Kv3.1b+ double-labeled cells constituted 90-99% of all Kv3.1b+ neurons. Parvalbumin+ neurons were also the main interneuronal subpopulation expressing the Kv3.2 potassium channel subunit. More than 67-78% of parvalbumin+ neurons were Kv3.2+, depending on the nucleus. However, these parvalbumin+/Kv3.2+ double-labeled cells constituted only 71-81% of all Kv3.2+ neurons. Most of the remaining neurons with significant levels of the Kv3.2 subunit were somatostatin+ interneurons. These Kv3.2-containing somatostatin+ interneurons constituted 27-50% of the somatostatin+ population, depending on the nucleus in question. These data suggest that both fast-firing and burst-firing parvalbumin+ interneurons in the basolateral amygdala express the Kv3.1b subunit. The significance of Kv3.2 expression in some parvalbumin+ and somatostatin+ interneurons remains to be determined.
Kv3.1和Kv3.2电压门控钾通道亚基的表达似乎对许多神经元群体的高频放电至关重要。在皮质中，这些亚基主要与含有小清蛋白或生长抑素的快速放电GABA能中间神经元相关。由于杏仁核基底外侧核复合体包含类似的中间神经元，因此确定这些钾通道亚基是否在这些相同的中间神经元亚群中表达很有意义。为了研究这个问题，采用过氧化物酶和双标记荧光免疫组织化学结合共聚焦激光扫描显微镜来确定大鼠杏仁核基底外侧核复合体中哪些中间神经元亚群表达Kv3.1b和Kv3.2亚基。使用针对小清蛋白、生长抑素、钙视网膜蛋白和胆囊收缩素的抗体来标记基底外侧杏仁核中间神经元的不同亚群。免疫过氧化物酶制剂检查表明，两种通道的表达都局限于基底外侧杏仁核中的非锥体中间神经元。胞体和近端树突被强烈染色，推测的篮状细胞和吊灯细胞产生的轴突终末被轻度染色。免疫荧光观察显示，小清蛋白阳性神经元是基底外侧杏仁核中表达Kv3.1b钾通道亚基的主要中间神经元亚群。根据核的不同，超过92% - 96%的小清蛋白阳性神经元是Kv3.1b阳性。这些小清蛋白阳性/Kv3.1b阳性双标记细胞占所有Kv3.1b阳性神经元的90% - 99%。小清蛋白阳性神经元也是表达Kv3.2钾通道亚基的主要中间神经元亚群。根据核的不同，超过67% - 78%的小清蛋白阳性神经元是Kv3.2阳性。然而，这些小清蛋白阳性/Kv3.2阳性双标记细胞仅占所有Kv3.2阳性神经元的71% - 81%。其余大部分具有显著水平Kv3.2亚基的神经元是生长抑素阳性中间神经元。这些含有Kv3.2的生长抑素阳性中间神经元占生长抑素阳性群体的27% - 50%，具体取决于所讨论的核。这些数据表明，基底外侧杏仁核中快速放电和爆发放电的小清蛋白阳性中间神经元都表达Kv3.1b亚基。Kv3.2在一些小清蛋白阳性和生长抑素阳性中间神经元中的表达意义仍有待确定。
