Laboratoire de Neurobiologie, CNRS UMR 7637, ESPCI ParisTech Paris, France.
Front Neural Circuits. 2012 Jun 29;6:36. doi: 10.3389/fncir.2012.00036. eCollection 2012.
IN THE NEOCORTEX, NEURONAL NITRIC OXIDE (NO) SYNTHASE (NNOS) IS ESSENTIALLY EXPRESSED IN TWO CLASSES OF GABAERGIC NEURONS: type I neurons displaying high levels of expression and type II neurons displaying weaker expression. Using immunocytochemistry in mice expressing GFP under the control of the glutamic acid decarboxylase 67k (GAD67) promoter, we studied the distribution of type I and type II neurons in the barrel cortex and their expression of parvalbumin (PV), somatostatin (SOM), and vasoactive intestinal peptide (VIP). We found that type I neurons were predominantly located in deeper layers and expressed SOM (91.5%) while type II neurons were concentrated in layer II/III and VI and expressed PV (17.7%), SOM (18.7%), and VIP (10.2%). We then characterized neurons expressing nNOS mRNA (n = 42 cells) ex vivo, using whole-cell recordings coupled to single-cell reverse transcription-PCR and biocytin labeling. Unsupervised cluster analysis of this sample disclosed four classes. One cluster (n = 7) corresponded to large, deep layer neurons, displaying a high expression of SOM (85.7%) and was thus very likely to correspond to type I neurons. The three other clusters were identified as putative type II cells and corresponded to neurogliaform-like interneurons (n = 19), deep layer neurons expressing PV or SOM (n = 9), and neurons expressing VIP (n = 7). Finally, we performed nNOS immunohistochemistry on mouse lines in which GFP labeling revealed the expression of two specific developmental genes (Lhx6 and 5-HT(3A)). We found that type I neurons expressed Lhx6 but never 5-HT(3A), indicating that they originate in the medial ganglionic eminence (MGE). Type II neurons expressed Lhx6 (63%) and 5-HT(3A) (34.4%) supporting their derivation either from the MGE or from the caudal ganglionic eminence (CGE) and the entopeduncular and dorsal preoptic areas. Together, our results in the barrel cortex of mouse support the view that type I neurons form a specific class of SOM-expressing neurons while type II neurons comprise at least three classes.
在新皮层中，神经元型一氧化氮合酶（nNOS）主要在两类 GABA 能神经元中表达：一类是表达水平较高的 I 型神经元，另一类是表达水平较弱的 II 型神经元。我们利用在谷氨酸脱羧酶 67k（GAD67）启动子控制下表达 GFP 的小鼠进行免疫细胞化学研究，研究了桶状皮层中 I 型和 II 型神经元的分布及其对 parvalbumin（PV）、somatostatin（SOM）和 vasoactive intestinal peptide（VIP）的表达。我们发现，I 型神经元主要位于较深的皮层，表达 SOM（91.5%），而 II 型神经元则集中在 II/III 层和 VI 层，并表达 PV（17.7%）、SOM（18.7%）和 VIP（10.2%）。然后，我们通过全细胞膜片钳记录结合单细胞逆转录 PCR 和生物素标记，对体外表达 nNOS mRNA 的神经元（n=42 个细胞）进行了特征描述。对该样本的无监督聚类分析揭示了四个细胞群。一个细胞群（n=7）对应于大的深层神经元，高表达 SOM（85.7%），因此很可能对应于 I 型神经元。另外三个细胞群被鉴定为假定的 II 型细胞，对应于神经胶质样中间神经元（n=19）、表达 PV 或 SOM 的深层神经元（n=9）和表达 VIP 的神经元（n=7）。最后，我们在 GFP 标记显示两种特定发育基因（Lhx6 和 5-HT3A）表达的小鼠品系上进行了 nNOS 免疫组织化学研究。我们发现，I 型神经元表达 Lhx6，但从不表达 5-HT3A，这表明它们起源于内侧神经节隆起（MGE）。II 型神经元表达 Lhx6（63%）和 5-HT3A（34.4%），支持它们来源于 MGE 或尾状神经节隆起（CGE）和脚间核和背侧视前区。总之，我们在小鼠桶状皮层中的研究结果支持以下观点：I 型神经元形成了一类特定的 SOM 表达神经元，而 II 型神经元至少包括三类。
