Table_4_Octopamine Shifts the Behavioral Response From Indecision to Approach or Aversion in Drosophila melanogaster.XLSX

Animals must make constant decisions whether to respond to external sensory stimuli or not to respond. The activation of positive and/or negative reinforcers might bias the behavioral response towards approach or aversion. To analyze whether the activation of the octopaminergic neurotransmitter system can shift the decision between two identical odor sources, we active in Drosophila melanogaster different sets of octopaminergic neurons using optogenetics and analyze the choice of the flies using a binary odor trap assay. We show that the release of octopamine from a set of neurons and not acetylcholine acts as positive reinforcer for one food odor source resulting in attraction. The activation of a subset of these neurons causes the opposite behavior and results in aversion. This aversion is due to octopamine release and not tyramine, since in Tyramine-β-hydroxylase mutants (Tβh) lacking octopamine, the aversion is suppressed. We show that when given the choice between two different attractive food odor sources the activation of the octopaminergic neurotransmitter system switches the attraction for ethanol-containing food odor to a less attractive food odor. Consistent with the requirement for octopamine in biasing the behavioral outcome, Tβh mutants fail to switch their attraction. The execution of attraction does not require octopamine but rather initiation of the behavior or a switch of the behavioral response. The attraction to ethanol also depends on octopamine. Pharmacological increases in octopamine signaling in Tβh mutants increase ethanol attraction and blocking octopamine receptor function reduces ethanol attraction. Taken together, octopamine in the central brain orchestrates behavioral outcomes by biasing the decision of the animal towards food odors. This finding might uncover a basic principle of how octopamine gates behavioral outcomes in the brain.

动物必须不断作出是否对外部感官刺激作出反应的决定。正强化剂和/或负强化剂的激活可能会使行为反应偏向趋近或回避。为了分析多巴胺胺能神经递质系统的激活是否能够改变动物在两种相同气味来源之间的决策，我们利用光遗传学在黑腹果蝇中激活不同组的多巴胺胺能神经元，并通过二元气味陷阱试验分析果蝇的选择。我们发现，一组神经元中多巴胺胺的释放而非乙酰胆碱作为某一食物气味来源的正强化剂，导致吸引行为。这些神经元子集的激活则引起相反的行为，导致回避。这种回避是由于多巴胺胺的释放而非酪胺引起的，因为在缺乏多巴胺胺的酪胺β-羟化酶突变体（Tβh）中，这种回避被抑制。我们显示，当在两种不同的吸引性食物气味来源之间作出选择时，多巴胺胺能神经递质系统的激活将乙醇含有的食物气味吸引转变为不那么吸引人的食物气味。与多巴胺胺在影响行为结果方面的需求一致，Tβh突变体无法改变它们的吸引。吸引行为的执行不需要多巴胺胺，而是行为的启动或行为反应的改变。对乙醇的吸引也依赖于多巴胺胺。在Tβh突变体中，多巴胺胺信号传递的药理学增加会增加乙醇的吸引力，而阻断多巴胺胺受体功能会减少乙醇的吸引力。综上所述，中枢脑中的多巴胺胺通过影响动物对食物气味的决策偏向来协调行为结果。这一发现可能揭示了一个关于多巴胺胺如何在脑中调控行为结果的基本原理。