Translation of odor information into innate olfactory ethanol preference

这项提议的目的是解开动物大脑中潜在的接近行为的机制。在自然界中，像树懒和果蝇这样的动物更喜欢发酵的食物来源。从食物来源散发出的乙醇气味会在很长一段时间内吸引动物。此前，我们已经表明，实验室中的成年黑腹果蝇更喜欢含有类似于自然界中发现的浓度的低乙醇食物气味(Ogueta等人，2010年)。一般来说，气味信息必须在不同的水平上进行处理，然后才能将该信息转换为行为反应。最初，气味必须被感知，动物必须在其内部环境的背景下评估这一信息。在这一步之后，动物必须决定是否对这种刺激做出反应，以及它是否会以接近行为做出反应。最后，必须执行运动程序，这样苍蝇才能真正到达食物来源。我们之前已经证明，至少有两种机制参与了动物向气味来源移动的决定。一种机制需要在感受器神经元水平上进行嗅觉信息处理，并涉及嗅觉共同受体或正式名称为Or83b(Schneider等人，2012年)。Orco是否在乙醇特定气味识别中发挥作用，或者Orco是否通常需要区分类似的复杂气味混合物尚不清楚，将在本提案中使用神经遗传学操作结合行为实验进行研究。缺乏神经递质章鱼胺的酪胺-b-羟基酶突变体的表型分析揭示了第二种机制。利用光遗传学激活八胺/酪胺能神经元增加了选择一个特定部位的可能性，这表明八胺/酪胺能神经递质系统是加强嗅觉乙醇偏好的机制和反应选择功能所必需的(Schneider等人，2012年)。然而，增强剂在调节嗅觉偏好中的作用以及它是否通过转移注意力而起作用尚不清楚，将在本提案中使用神经解剖学方法和光遗传操作结合行为实验来解决。综合起来，这两种方法将有助于我们理解行为反应是如何从大脑中挑选出来的。

The aim of the proposal is to unravel mechanisms in the animal brain underlying approach behavior. In nature animals like treeshrews and the fruit flies prefer fermenting food sources. The ethanol odor emanating from the food source attracts animals over a long range. Previously, we have shown that adult Drosophila melanogaster flies in the lab prefer low ethanol containing food odors similar at concentrations that are also found in nature (Ogueta et al., 2010). In general, odor information has to be processed at different levels before this information is converted into a behavioral response. Initially, the odor has to be perceived and the animal has to evaluate this information in the context of its internal environment. After this step the animal has to decide whether to react to this stimulus or not and whether it will respond with approach behavior. Finally motor programs have to be executed so that the fly indeed reaches the food source. We have previously shown that at least two mechanisms are involved in the decision of an animal to move towards odor source. One mechanism requires olfactory information processing at the level of the receptor neurons and involved the olfactory co-receptor Orco - formally known as Or83b (Schneider et al., 2012). Whether Orco functions in ethanol specific odor recognition or whether Orco is in general required to distinguish similar complex odor mixtures is not know yet and will be investigated in this proposal using neuro-genetic manipulations combined with behavioral experiments. The phenotypic analysis of Tyramine-b-hydroxylase mutants lacking the neurotransmitter octopamine uncovered a second mechanism. Activation of octopaminergic/tyraminergic neurons using opto-genetics increased the likelihood to choose one specific site over another suggesting that the octopaminergic/tyraminergic neurotransmitter system is required for reinforcing mechanisms underlying olfactory ethanol preference and functions in response selection (Schneider et al., 2012). However, where the reinforcer acts in mediating olfactory preference and whether it acts through shifting of attention is not known and will be addressed in this proposal using neuro-anatomical methods and opto-genetic manipulations combined with behavioral experiments. Taken together both approaches will foster our understanding of how behavioral responses are selected from the brain.