Functional properties of dopaminergic neurones in the mouse olfactory bulb
Functional properties of dopaminergic neurones in the mouse olfactory bulb
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DOI：
10.1113/jphysiol.2005.084632
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发表时间：
2005-04
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影响因子：
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通讯作者：
A. Pignatelli;Kazuto Kobayashi;H. Okano;O. Belluzzi
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作者：
A. Pignatelli;Kazuto Kobayashi;H. Okano;O. Belluzzi
哺乳动物的嗅球在肾小球层内含有大量的多巴胺能神经元。多巴胺在体内和体外都被证明可以调节嗅觉信息处理的几个方面，但由于无法识别活的制剂中的这些细胞，多巴胺能神经元的功能特性从未被描述过。为了克服这一困难，我们使用了一个转基因小鼠品系，该品系在酪氨酸羟基酶的启动子下构建了一个EGFP(增强型绿色荧光蛋白)报告结构，酪氨酸羟基酶是合成氨基可拉明的限速酶。结果，我们能够在活的制剂中识别出多巴胺能神经元(TH-GFP细胞)，并且，我们第一次能够研究这种神经元在嗅球中的功能特性，在切片和分离的细胞中。这些细胞最显著的特征是自律性。在这些细胞中，我们确定了五种主要的电压依赖电导：其中幅度最大的两种是快速瞬变Na+电流和延迟整流K+电流。此外，我们观察到三个较小的内向电流，由Na+离子(持续型)和由钙离子(LVA和HVA)维持。利用药理学工具和离子替代方法，我们证明了起搏过程是由持续的Na+电流和T型钙电流的相互作用支持的。我们对这些细胞中存在的五种电导进行了完整的运动学分析，并开发了TH-GFP细胞的Hodgkin-Huxley模型，该模型能够准确地再现活细胞的属性，包括自律性，并允许精确地理解这一过程。
The olfactory bulb of mammals contains a large population of dopaminergic interneurones within the glomerular layer. Dopamine has been shown both in vivo and in vitro to modulate several aspects of olfactory information processing, but the functional properties of dopaminergic neurones have never been described due to the inability to recognize these cells in living preparations. To overcome this difficulty, we used a transgenic mouse strain harbouring an eGFP (enhanced green fluorescent protein) reporter construct under the promoter of tyrosine hydroxylase, the rate‐limiting enzyme for cathecolamine synthesis. As a result, we were able to identify dopaminergic neurones (TH‐GFP cells) in living preparations and, for the first time, we could study the functional properties of such neurones in the olfactory bulb, in both slices and dissociated cells. The most prominent feature of these cells was the autorhythmicity. In these cells we identified five main voltage‐dependent conductances: the two having largest amplitude were a fast transient Na+ current and a delayed rectifier K+ current. In addition, we observed three smaller inward currents, sustained by Na+ ions (persistent type) and by Ca2+ ions (LVA and HVA). Using pharmacological tools and ion substitution methods we showed that the pacemaking process is supported by the interplay of the persistent Na+ current and of a T‐type Ca2+ current. We carried out a complete kinetical analysis of the five conductances present in these cells, and developed a Hodgkin‐Huxley model of TH‐GFP cells, capable of reproducing accurately the properties of living cells, including autorhytmicity, and allowing a precise understanding of the process.