Effects of fear learning on early olfactory processing

描述(申请人提供)：感觉系统生理学在两个更高的顺序(Li et al.2008年；Edeline&Weinberger 1991；Gdalyahu等人。(2012)和早期(Fletcher 2012)处理中心可以通过情绪学习进行修改。事实上，感觉病理是许多情感障碍的共同因素，从创伤后应激障碍的彻底幻觉(Mueser&Butler 1987；Freeman&Fowler 2009)到注意力处理的更微妙的变化(Desseilles等人)。2009年；Adenauer等人。这可能会使焦虑症中传入的感觉信息偏向于威胁预测刺激(Beck&Clark 1997；Buckley 2000)。焦虑障碍通常在动物模型中使用关联恐惧条件反射范式进行研究，在该范式中，动物了解到中性感觉刺激，如气味(CS+)，预测了厌恶刺激的发生，如足部电击。这些模型为研究感觉加工在情绪学习中的作用提供了一个独特的机会，在初步研究中，我们发现辨别性嗅觉恐惧条件作用导致嗅觉感觉神经元(OSNs)CS+诱发的神经递质释放惊人地增加，OSNs是大脑的主要(第一)感觉输入。这种增强可能有助于以后发现CS+或将注意力集中在类似的感觉刺激上，或者可能是适应不良并导致焦虑。为了进一步研究早期感觉处理和类焦虑状态之间的联系，这项研究将在接受辨别性嗅觉恐惧条件反射的小鼠身上进行纵向的体内生理和形态光学成像程序。气味诱发的OSN突触输出到嗅球肾小球将通过在基线时植入背侧嗅球上方的双侧颅窗，在恐惧学习后，并在消退学习后再次在单个小鼠中表达突触Hluorin(SPH)胞吐指示器，在所有成熟的OSN轴突终末(Bozza等人)。2004年)。在其OSN轴突终末加载了钙敏感染料的小鼠中，突触前嗅觉锁定的钙信号将在恐惧条件作用前后被可视化，以评估CS+反应的OSN的气味诱发反应动力学如何被情绪学习所改变。在体内，将对生理成像实验中识别的肾小球进行基于双光子的形态计量分析，以评估OSN肾小球神经支配的潜在结构可塑性(Jones等人。2008年)。我们的初步数据表明，CS+的增强表征是通过嗅球回路的变化来调节的，嗅球回路负责控制传入的感觉信息(即，情绪学习可能会导致大门打开)。为了在经历恐惧条件反射的小鼠身上测试这一点，我们将药理学地操纵突触前调节OSN活动的肾小球内回路，电刺激嗅神经，并直接在GABA能间神经元中可视化气味诱发活性，这些神经元在突触前抑制OSN轴突终末的神经递质释放(在GAD65能神经元中表达基因编码的钙指示物GCamP3的小鼠)。

DESCRIPTION (provided by applicant): Sensory system physiology in both higher order (Li et al. 2008; Edeline & Weinberger 1991; Gdalyahu et al. 2012) and early (Fletcher 2012) processing centers can be modified by emotional learning. Sensory pathologies are in fact a common element of many affective disorders, ranging from outright hallucinations in post traumatic stress disorder (Mueser & Butler 1987; Freeman & Fowler 2009) to more subtle changes in attentional processing (Desseilles et al. 2009; Adenauer et al. 2010) which may bias incoming sensory information to threat-predictive stimuli in anxiety disorders (Beck & Clark 1997; Buckley 2000). Anxiety disorders are routinely studied in animal models using associative fear conditioning paradigms, in which an animal learns that a neutral sensory stimulus, such as an odor (the CS+), predicts the occurrence of an aversive stimulus, such as a footshock. Such models provide a unique opportunity to investigate the role of sensory processing in emotional learning, and in preliminary studies we found that discriminative olfactory fear conditioning causes a surprising enhancement of CS+-evoked neurotransmitter release from olfactory sensory neurons (OSNs), the primary (first) sensory inputs to the brain. This enhancement may be beneficial in facilitating later detection of the CS+ or focusing attention towards similar sensory stimuli, or alternatively, may be maladaptive and contribute to anxiety. To further investigate the associations between early sensory processing and anxiety-like states, this study will perform longitudinal in vivo physiological and morphometric optical imaging procedures in mice that undergo discriminative olfactory fear conditioning. Odorant-evoked OSN synaptic output to olfactory bulb glomeruli will be visualized through a bilateral cranial window implanted above the dorsal olfactory bulbs at baseline, after fear learning, and again after extinction learning in individual mice expressing the synaptopHluorin (spH) exocytosis indicator in all mature OSN axon terminals (Bozza et al. 2004). Presynaptic sniff-locked Ca2+ signals in mice whose OSN axon terminals have been loaded with calcium-sensitive dye will be visualized before and after fear conditioning to assess how odorant-evoked response dynamics of CS+-responsive OSNs are modified by emotional learning. In vivo two-photon-based morphometric analyses will be performed on glomeruli identified during physiological imaging experiments to assess potential structural plasticity in OSN glomerular innervation (Jones et al. 2008). Our preliminary data suggest that the enhanced representation of the CS+ is mediated by changes in the olfactory bulb circuitry that gates incoming sensory information (i.e., emotional learning may cause the gate to open). To test this in vivo in mice that undergo fear conditioning, we will pharmacologically manipulate the intraglomerular circuit that presynaptically modulates OSN activity, electrically stimulate the olfactory nerve, and directly visualize odor- evoked activity n GABAergic interneurons that presynaptically inhibit neurotransmitter release from OSN axon terminals (in mice expressing the genetically-encoded Ca2+ indicator GCamP3 in GAD65-ergic interneurons).