Imaging Odor-Evoked Activities in the Mouse Olfactory Bulb using Optical Reflectance and Autofluorescence Signals
Imaging Odor-Evoked Activities in the Mouse Olfactory Bulb using Optical Reflectance and Autofluorescence Signals
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DOI：
10.3791/3336
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发表时间：
2011-10-01
影响因子：
1.2
通讯作者：
Gurden, Hirac
中科院分区：
文献类型：
--
作者：
Chery, Romain;L'Heureux, Barbara;Gurden, Hirac
在大脑中，感觉刺激激活了参与刺激编码的功能模块中分布的神经元群体。功能光学成像技术有利于以高空间分辨率可视化感觉皮层中这些模块的激活。在这种情况下，由与神经能量学相关的分子机制产生的内源性光学信号是记录啮齿动物大脑宽范围内感觉刺激空间图的宝贵对比来源。在这里，我们提出了两种基于脑组织内源性光学特性变化的技术激活期间。首先，固有光信号（IOS）由红光反射率的局部改变产生，这是由于：（i）血氧水平和血液体积的变化引起的吸收（ii）光子散射。使用体内IOS记录空间图始于20世纪80年代中期，当时观察到大鼠胡须桶的光学图和猫视觉皮层中的方向柱（1）。随后，Larry Katz的研究小组证实了啮齿动物主嗅球（OB）表面对气味的反应的IOS成像（2）。第二种方法依赖于黄素蛋白自发荧光信号（FAS），由于这些线粒体代谢中间产物的氧化还原状态的变化。更确切地说，该技术是基于当组织被蓝光激发时由于黄素蛋白的氧化状态而产生的绿色荧光。虽然这些信号可能是布里顿·钱斯及其同事的先驱研究中记录的第一批用于研究大脑活动的荧光分子之一（3），但直到最近，它们才被用于绘制体内大脑活动的地图。Katsuei Shibuki的研究小组首次将FAS成像应用于啮齿动物的体感皮质，以响应后爪刺激（4）。嗅觉系统对于绝大多数生物物种的生存至关重要，因为它可以有效地检测和识别化学物质环境（食物、捕食者）。嗅球是大脑中嗅觉信息处理的第一个中继。它接受来自嗅觉初级感觉神经元的传入投射，这些神经元检测挥发性气味分子。每个感觉神经元只表达一种类型的气味受体，携带同种类型受体的神经元将它们的神经突起发送到由离散的神经元组成的相同的100 μ m（3）的明确的微区域，即嗅球（图1）。在过去的十年中，IOS成像促进了OB5，6，7的功能探索，OB5，6，7已成为研究最多的感觉结构之一。OB活动与FAS成像的映射尚未进行。在这里，我们显示了一个有效的协议IOS和FAS成像映射气味诱发的活动在小鼠OB的连续步骤。
In the brain, sensory stimulation activates distributed populations of neurons among functional modules which participate to the coding of the stimulus. Functional optical imaging techniques are advantageous to visualize the activation of these modules in sensory cortices with high spatial resolution. In this context, endogenous optical signals that arise from molecular mechanisms linked to neuroenergetics are valuable sources of contrast to record spatial maps of sensory stimuli over wide fields in the rodent brain.Here, we present two techniques based on changes of endogenous optical properties of the brain tissue during activation. First the intrinsic optical signals (IOS) are produced by a local alteration in red light reflectance due to: (i) absorption by changes in blood oxygenation level and blood volume (ii) photon scattering. The use of in vivo IOS to record spatial maps started in the mid 1980's with the observation of optical maps of whisker barrels in the rat and the orientation columns in the cat visual cortex(1). IOS imaging of the surface of the rodent main olfactory bulb (OB) in response to odorants was later demonstrated by Larry Katz's group(2). The second approach relies on flavoprotein autofluorescence signals (FAS) due to changes in the redox state of these mitochondrial metabolic intermediates. More precisely, the technique is based on the green fluorescence due to oxidized state of flavoproteins when the tissue is excited with blue light. Although such signals were probably among the first fluorescent molecules recorded for the study of brain activity by the pioneer studies of Britton Chances and colleagues(3), it was not until recently that they have been used for mapping of brain activation in vivo. FAS imaging was first applied to the somatosensory cortex in rodents in response to hindpaw stimulation by Katsuei Shibuki's group(4).The olfactory system is of central importance for the survival of the vast majority of living species because it allows efficient detection and identification of chemical substances in the environment (food, predators). The OB is the first relay of olfactory information processing in the brain. It receives afferent projections from the olfactory primary sensory neurons that detect volatile odorant molecules. Each sensory neuron expresses only one type of odorant receptor and neurons carrying the same type of receptor send their nerve processes to the same well-defined microregions of (similar to)100 mu m(3) constituted of discrete neuropil, the olfactory glomerulus (Fig. 1). In the last decade, IOS imaging has fostered the functional exploration of the OB5,6,7 which has become one of the most studied sensory structures. The mapping of OB activity with FAS imaging has not been performed yet.Here, we show the successive steps of an efficient protocol for IOS and FAS imaging to map odor-evoked activities in the mouse OB.