Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Cereb Cortex. 2011 Nov;21(11):2639-49. doi: 10.1093/cercor/bhr051. Epub 2011 Apr 5.
To characterize connexin36 (Cx36)-expressing neurons of the adult rat somatosensory cortex, we examined fluorescence signals for Cx36 messenger RNA (mRNA) in 3 nonoverlapping subpopulations of γ-aminobutyric acid (GABA)ergic interneurons, which showed immunoreactivity for 1) parvalbumin (PV); 2) somatostatin (SOM); and 3) either calretinin (CR), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), or choline acetyltransferase (ChAT). About 80% of PV-, 52% of SOM-, 37% of CR/VIP/CCK/ChAT-immunoreactive cells displayed Cx36 signals across all cortical layers, and inversely 64%, 25%, and 9% of Cx36-expressing neurons were positive for PV, SOM, or CR/VIP/CCK/ChAT, respectively. Notably, although almost all Cx36-expressing neurons in layer (L) 4, L5, and L6 were positive for one of these markers, a substantial proportion of those in L1 (91%) and L2/3 (10%) were negative for the markers tested, suggesting that other types of neurons might express Cx36. We further investigated the colocalization of Cx36 mRNA and α-actinin2 immunoreactivity, as a marker for late-spiking GABAergic neurons, by using mirror-image sections. Surprisingly, more than 77% of α-actinin2-positive cells displayed Cx36 signals in L1-L3, and about 49% and 13% of Cx36-expressing neurons were positive for α-actinin2 in L1 and L2/3, respectively. These findings suggest that all the subtypes of GABAergic interneurons might form gap junctions in the neocortex.
为了描述成年大鼠体感皮层中连接蛋白 36(Cx36)表达神经元的特征,我们在 3 种非重叠的γ-氨基丁酸(GABA)能中间神经元亚群中检测了 Cx36 信使 RNA(mRNA)的荧光信号,这些中间神经元对 1)parvalbumin(PV);2)somatostatin(SOM);和 3)calretinin(CR)、vasoactive intestinal polypeptide(VIP)、cholecystokinin(CCK)或choline acetyltransferase(ChAT)中的一种有免疫反应性。大约 80%的 PV-、52%的 SOM-、37%的 CR/VIP/CCK/ChAT-免疫反应性细胞在所有皮层层中都显示出 Cx36 信号,相反,64%、25%和 9%的 Cx36 表达神经元分别对 PV、SOM 或 CR/VIP/CCK/ChAT 呈阳性。值得注意的是,尽管 L4、L5 和 L6 层中的几乎所有 Cx36 表达神经元都对这些标志物中的一种呈阳性,但 L1(91%)和 L2/3(10%)中的相当一部分神经元对测试的标志物呈阴性,这表明可能有其他类型的神经元表达 Cx36。我们进一步通过镜像切片研究了 Cx36 mRNA 和 α-actinin2 免疫反应性的共定位,α-actinin2 作为迟发性 GABA 能神经元的标志物。令人惊讶的是,超过 77%的α-actinin2 阳性细胞在 L1-L3 中显示 Cx36 信号,大约 49%和 13%的 Cx36 表达神经元在 L1 和 L2/3 中对α-actinin2 呈阳性。这些发现表明,所有 GABA 能中间神经元亚型都可能在新皮层中形成缝隙连接。