Functional role of Gastrin Releasing Peptide (GRP) and GRP expressing neurons in the gustatory cortex

项目摘要 众所周知，啮齿动物味觉皮层（GC）中的神经活动编码味觉，味觉预测 线索和口味引导的决定。这些神经信号在指导与以下相关的行为方面发挥着重要作用： 品味和消费。最近的电生理和成像研究表明，GC也可以处理 与进食和饮水的稳态控制有关的内感受性信息，饥饿/饱腹感， 口渴/解渴影响正在进行的活动的慢时间尺度和快时间尺度上的神经活动 味觉和线索诱发的活动。参与内感受性加工的GC回路和神经化学物质 信号以及它们在驱动特定行为反应中的作用尚未完全理解。 我们建议通过关注一种神经肽，胃泌素释放肽（GRP）和一种神经肽来解决这一差距。 产生GRP的神经元的GC群体。由于GRP是一种摄食抑制肽，因此表达GRP的神经元 (GRP+）是感测体内平衡状态和介导GC对消耗的影响的理想候选者。我们 初步数据显示，GC GRP+神经元投射到杏仁核基底外侧核（BLA）- a 以其在调解厌恶和食欲行为中的作用而闻名的核-证实了这一观点， 细胞群确实可以控制行为并导致进食终止。 在这个提议中，我们将测试GC GRP+神经元处理的总体假设， 内感受性稳态信号在慢和快的时间尺度的持续和味道/线索， 诱发活动，并能够抑制消费。解剖学和免疫组织学方法， 体外膜片钳电生理学，行为小鼠中的2-光子（2 P）钙成像， 光遗传学/药理学操作将用于解决以下具体目标： 解剖学方法，膜片钳和光遗传学，以建立神经化学身份，电生理 GC GRP+神经元的性质、层状分布和连接性。这些研究将检验以下假设： GC GRP+神经元是向BLA发出投射的兴奋性神经元， 调节BLA回路的活动。目标#2将使用2 P钙成像研究GRP+的活动模式 和GRP-神经元参与行为任务探测味道和预期线索处理下的小鼠 独特的自我平衡条件这些实验将检验GC GRP+神经元的活性， 特别是那些投射到BLA的，整合与营养物质（味道和线索）相关的感觉信号， 与进餐终止相关的稳态信号。最后，目标#3将依赖于在不同时间点的光遗传学激活。 建立GC GRP+神经元的行为贡献并研究神经化学 这种效果的基础。实验将检验GC GRP+神经元提供进餐终止的假设。 信号，并且它们向BLA的投射至少部分地介导进食行为的控制。 总之，本实验为GC和GC双BLA电路的研究开辟了一条新的途径 参与表达内感受信号和指导自我平衡行为。如果成功，这些研究将 i）增强我们对味觉皮层功能的理解; ii）揭示皮层GRP在味觉皮层中的新作用。 GRP β BLA轴; iii）建立用于研究皮质-杏仁回路中的肽能传递的模型。的 这些结果将对我们理解GC在摄食行为中的作用产生重要影响。

PROJECT SUMMARY It is well-established that neural activity in the rodent gustatory cortex (GC) encodes taste, taste-predictive cues and taste-guided decisions. These neural signals play an important role in guiding behaviors related to taste and consumption. Recent electrophysiological and imaging studies demonstrated that GC can also process interoceptive information pertaining to the homeostatic control of feeding and drinking, with hunger/satiety and thirst/quenching affecting neural activity on both the slow time scale of ongoing activity and the fast time scale of taste- and cue-evoked activity. The GC circuits and neurochemicals involved in processing interoceptive signals as well as their role in driving specific behavioral responses are not fully understood yet. We propose to address this gap by focusing on a neuropeptide, the gastrin-releasing peptide, (GRP), and a GC population of neurons producing GRP. As GRP is a feeding-suppressing peptide, neurons expressing GRP (GRP+) are ideal candidates to sense homeostatic states and mediate the effects of GC on consumption. Our preliminary data show that GC GRP+ neurons project to the basolateral nucleus of the amygdala (BLA) – a nucleus known for its role in mediating aversive and appetitive behaviors – corroborating the idea that this population of cells may indeed control behavior and lead to meal termination. The experiments in this proposal we will test the overarching hypothesis that GC GRP+ neurons process interoceptive homeostatic signals at both the slow and fast temporal scales of ongoing and taste/cue- evoked activity, and are capable of inhibiting consumption. Anatomical and immunohistological methods, in vitro patch clamp electrophysiology, 2-photon (2P) calcium imaging in behaving mice, and optogenetic/pharmacological manipulations will be used to address the following specific aims: Aim #1 will rely on anatomical methods, patch clamp and optogenetics to establish neurochemical identity, electrophysiological properties, laminar distribution and connectivity of GC GRP+ neurons. The studies will test the hypothesis that GC GRP+ neurons are excitatory neurons sending projections to BLA and that GRP released by these neurons modulates the activity of BLA circuits. Aim #2 will use 2P calcium imaging to study the activity patterns of GRP+ and GRP- neurons in mice engaged in behavioral tasks probing taste and anticipatory-cues processing under distinct homeostatic conditions. These experiments will test the hypothesis that activity of GC GRP+ neurons, and specifically those projecting to BLA, integrate sensory signals related to nutrients (taste and cues) with homeostatic signals related to meal termination. Finally, Aim #3 will rely on optogenetic activation at different time scales to establish the behavioral contribution of GC GRP+ neurons and investigate the neurochemical bases of this effect. The experiments will test the hypothesis that GC GRP+ neurons provide a meal termination signal, and that their projection to BLA mediates, at least in part, the control of feeding behavior. Altogether, the proposed experiments will establish a new research avenue on the GC and GCBLA circuits involved in representing interoceptive signals and guiding homeostatic behaviors. If successful, these study will i) enhance our understanding of the function of the gustatory cortex; ii) unveil a new role for cortical GRP within the GRPBLA axis; iii) establish a model for studying peptidergic transmission in cortico-amygalar circuits. The results will have important consequences for our understanding of the role of GC in ingestive behaviors.