Duchamp-Viret P, Duchamp A, Chaput M A
Laboratoire de Neurosciences et Systèmes Sensoriels, Unité Mixte de Recherche, Centre National de la Recherche Scientifique-Université Claude Bernard Lyon 1, 69622 Villeurbanne cedex, France.
J Neurosci. 2000 Mar 15;20(6):2383-90. doi: 10.1523/JNEUROSCI.20-06-02383.2000.
In mammals, two recent studies have shown recently that one odor molecule can be recognized by several molecular olfactory receptors (ORs), and a single OR can recognize multiple odor molecules. In addition, one olfactory receptor neuron (ORN) may respond to different stimuli chosen as representative of distinct odor qualities. The aim of the present study was to analyze quality and intensity coding abilities of rat single ORNs, comparing them with previous extensive data gathered in the frog to get insight into the generality of olfactory coding mechanisms over vertebrates. Response properties of 90 rat ORNs to different odors or to one odor at different concentrations were analyzed. In the rat and the frog, odor quality appears to be specified through the identity of activated ORNs. However, rat ORNs have higher response thresholds. This lower sensitivity may be interpreted as an increase in selectivity of rat ORNs for low or medium odor intensities. In these conditions, the lower proportion of activated ORNs could be counterbalanced by their number, as well as by their higher glomerular convergence ratio in the olfactory bulb. From amphibians to mammals, the olfactory system appears to use universal mechanisms based on a combinatorial-coding mode that may allow quasi-infinite possibilities of adaptation to various olfactory environments.
在哺乳动物中，最近的两项研究表明，一种气味分子可被多种分子嗅觉受体（OR）识别，且单个OR能识别多种气味分子。此外，一个嗅觉受体神经元（ORN）可能对被选为不同气味特征代表的不同刺激产生反应。本研究的目的是分析大鼠单个ORN的特征和强度编码能力，并将其与先前在青蛙中收集的大量数据进行比较，以深入了解脊椎动物嗅觉编码机制的普遍性。分析了90个大鼠ORN对不同气味或对一种气味在不同浓度下的反应特性。在大鼠和青蛙中，气味特征似乎是通过被激活的ORN的特性来确定的。然而，大鼠ORN具有更高的反应阈值。这种较低的敏感性可被解释为大鼠ORN对低或中等气味强度的选择性增加。在这些情况下，被激活的ORN比例较低可通过其数量以及它们在嗅球中较高的肾小球会聚率来平衡。从两栖动物到哺乳动物，嗅觉系统似乎使用基于组合编码模式的通用机制，这可能允许对各种嗅觉环境进行几乎无限的适应可能性。
