Neurobiology Unit and Program in Basic and Applied Neurosciences, Cell Biology Department, Universitat de València, Spain.
Neuroscience. 2011 May 5;181:18-27. doi: 10.1016/j.neuroscience.2011.03.004. Epub 2011 Mar 5.
The piriform cortex layer II of young-adult rats presents a population of prenatally generated cells, which express immature neuronal markers, such as the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) or doublecortin (DCX), and display structural characteristics of immature neurons. The number of PSA-NCAM/DCX expressing cells in this region decreases markedly as age progresses, suggesting that these cells differentiate or die. Since the piriform cortex receives a major input from the olfactory bulb and participates in olfactory information processing, it is possible that the immature neurons in layer II are affected by manipulations of the olfactory bulb or olfactory learning. It is not known whether these cells can be induced to differentiate and, if so, what would be their fate. In order to address these questions, we have performed unilateral olfactory bulbectomy (OBX) and an olfactory learning paradigm (taste-potentiated odor aversion, TPOA), in young-adult rats and have studied the expression of different mature and immature neuronal markers, as well as the presence of cell death. We have found that 14 h after OBX there was a dramatic decrease in the number of both PSA-NCAM and DCX expressing cells in piriform cortex layer II, whereas that of cells expressing NeuN, a mature neuronal marker, increased. By contrast, the number of cells expressing glutamate decarboxylase, isoform 67 (GAD67), a marker for interneurons, decreased slightly. Additionally, we have not found evidence of numbers of dying cells high enough to justify the disappearance of immature neurons. Analysis of animals subjected to TPOA revealed that this paradigm does not affect PSA-NCAM expressing cells. Our results strongly suggest that OBX can induce the maturation of immature neurons in the piriform cortex layer II and that these cells do not become interneurons. By contrast, these cells do not seem to play a crucial role in olfactory memory.
成年早期大鼠的梨状皮层 II 层存在一群产前产生的细胞，这些细胞表达未成熟的神经元标志物，如神经细胞黏附分子的多涎酸化形式（PSA-NCAM）或双皮质素（DCX），并表现出未成熟神经元的结构特征。随着年龄的增长，该区域表达 PSA-NCAM/DCX 的细胞数量明显减少，这表明这些细胞分化或死亡。由于梨状皮层从嗅球接收主要输入，并参与嗅觉信息处理，因此 II 层中的未成熟神经元可能受到嗅球操作或嗅觉学习的影响。目前尚不清楚这些细胞是否可以被诱导分化，如果可以，它们的命运将如何。为了解决这些问题，我们在成年早期大鼠中进行了单侧嗅球切除术（OBX）和嗅觉学习范式（味觉增强的厌恶，TPOA），并研究了不同成熟和未成熟神经元标志物的表达，以及细胞死亡的存在。我们发现，OBX 后 14 小时，梨状皮层 II 层中表达 PSA-NCAM 和 DCX 的细胞数量急剧减少，而表达成熟神经元标志物 NeuN 的细胞数量增加。相比之下，表达谷氨酸脱羧酶、同工型 67（GAD67）的细胞数量略有减少，GAD67 是中间神经元的标志物。此外，我们没有发现足够高的死亡细胞数量来证明未成熟神经元的消失。对接受 TPOA 的动物进行分析表明，该范式不会影响表达 PSA-NCAM 的细胞。我们的研究结果强烈表明，OBX 可以诱导梨状皮层 II 层未成熟神经元的成熟，而这些细胞不会成为中间神经元。相比之下，这些细胞似乎在嗅觉记忆中不起关键作用。
