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

项目总结 众所周知，啮齿动物味觉皮质(GC)中的神经活动编码味觉，味觉预测 线索和品味指导的决定。这些神经信号在引导相关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 与进食和饮水的动态平衡控制有关的相互感觉信息，以及饥饿/饱腹感和 口渴/解渴对正在进行的活动的慢时间尺度和快时间尺度的神经活动的影响 味觉和暗示所引起的活动。参与内感加工的GC回路和神经化学物质 信号及其在驱动特定行为反应中的作用尚不完全清楚。 我们建议通过专注于神经肽、胃泌素释放肽(GRP)和一种 产生GRP的神经元的GC群体。由于GRP是一种摄食抑制肽，所以表达GRP的神经元 (GRP+)是感知体内平衡状态和调节GC对消费影响的理想候选者。我们的 初步数据显示，GC GRP+神经元投射到杏仁基底外侧核(BLA-a) 核团因其在调节厌恶和食欲行为中的作用而闻名--证实了这一观点 细胞的数量确实可能控制行为，并导致用餐终止。 在本提案中的实验中，我们将检验GC GRP+神经元处理的主要假设 在持续和味觉/线索的慢和快时间尺度上的感觉内稳态信号- 诱发的活动，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，行为小鼠的双光子(2P)钙成像，以及 光遗传/药理学操作将用于解决以下具体目标：目标1将依赖于 建立神经化学同一性、电生理的解剖学方法、膜片钳和光遗传学 GC-GRP+神经元的性质、板层分布和连接。这些研究将检验这一假设 GC GRP+神经元是向BLA发送投射的兴奋性神经元，这些神经元释放GRP 调节BLA电路的活动。目标2将使用2P钙成像来研究GRP+的活动模式 小鼠参与味觉探测和预期线索加工的行为任务的GRP神经元 独特的动态平衡条件。这些实验将检验这样一种假设，即GC GRP+神经元的活动， 特别是那些投射到血乳酸的信号，将与营养(味道和线索)相关的感觉信号与 与终止进餐有关的动态平衡信号。最后，Aim#3将在不同的时间依赖于光遗传激活 建立GC-GRP+神经元行为贡献和神经化学研究的时间尺度 这种效果的基础。这些实验将验证GC GRP+神经元提供进食终止的假设 它们向BLA的投射至少在一定程度上调节了取食行为的控制。 总之，拟议的实验将为GC和GCBLA电路建立一条新的研究途径 参与代表感觉间信号和引导内环境平衡行为。如果成功，这些研究将 I)加强我们对味觉皮质功能的理解；ii)揭示皮质GRP在 -Bla轴；iii)建立研究皮质-杏仁核回路中肽能传递的模型。这个 结果将对我们理解GC在进食行为中的作用产生重要的影响。

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.