Role of PBN Subnuclei in Oromotor Behaviors

味觉信息通过神经从口腔传递到大脑，这些神经终止于延髓的一部分，称为孤束核(NST)。NST与脑干的另一部分相互连接，称为臂旁核(PBN)。PBN和NST都是味觉信息的处理和分发中心。它们将一些味觉信息发送到更高级的大脑中心，这样就可以感觉到味道的质量。PBN和NST还将输出发送到脑干中的运动中枢，该中枢对味觉输入产生运动反应。在PBN内，有两个不同的区域对味觉输入做出反应。其中一个区域(CM/VL)对舌前部的盐味反应最好，而另一个区域(EM/EL)对舌后部的苦味反应最好。由于对味觉输入的反应不同，推测这两个PBN区域控制着不同的运动反应。具体地说，假设CM/VL控制进食行为(如嘴巴运动和舌头伸出)，而EM/EL控制厌恶行为(如张口)。生物学和心理学本科生和他们的教师导师将通过刺激PBN的离散区域来解决这些假设，同时观察运动反应。该程序将允许构建PBN的功能图。具体地说，CM/VL和EM/EL将通过植入电极-套管系统在不同的清醒大鼠组中受到刺激。首先，这些区域将受到电刺激，同时口腔运动行为将被录像。电刺激后，通过插管将谷氨酸(一种兴奋性神经递质)注入PBN内的同一位置。电刺激和化学刺激的结合将使人们能够准确评估导致行为影响的特定神经元素。运动反应将与刺激部位的组织学定位相关。如前所述，基于前人的研究结果，我们假设刺激CM/VL会产生进食行为，而刺激EM/EL会引起厌恶反应。本研究采用一个简单的策略来定义味觉反应PBN区域对口腔运动行为的影响。该项目对理解味觉输入的中央处理和PBN的功能的潜在影响是巨大的。具体地说，阐明PBN内的功能地形图(MAP)将显著提高对味觉输入产生口腔运动反应的中枢机制的理解。

Taste information travels from the mouth to the brain within nerves that terminate in a part of the medulla oblongata called the nucleus of the solitary tract (NST). The NST is interconnected with another part of the brainstem called the parabrachial nucleus (PBN). Both the PBN and NST act as processing and distribution centers for taste information. They send some taste information to higher brain centers so that the taste quality can be perceived. The PBN and NST also send outputs to motor centers in the brainstem that produce motor responses to the taste input. Within the PBN, there are two distinct regions that respond to taste input. One of these regions (CM/VL) responds best to salt on the anterior tongue while the other (EM/EL) responds best to bitter taste on the posterior tongue. Due to this difference in responses to taste input, it is hypothesized that the two PBN areas control different motor responses. Specifically, it is hypothesized that CM/VL controls ingestive behaviors (like mouth movements and tongue protrusions) while EM/EL controls aversive behaviors (like gapes). Undergraduate Biology and Psychology students and their faculty mentors, will address these hypotheses by stimulating discrete areas of the PBN while observing motor responses. This procedure will allow the construction of a functional map of the PBN. Specifically, CM/VL and EM/EL will be stimulated in separate groups of conscious rats using implanted electrode-cannula systems. First, these areas will be electrically stimulated while oral motor behaviors are videotaped. Following electrical stimulation, injection of glutamate (an excitatory neurotransmitter) through the cannula into the same location within the PBN will occur. The combination of electrical and chemical stimulation will allow accurate assessment of the specific neural elements responsible for the behavioral effects. The motor responses will be correlated with the histological localization of the stimulation sites. As mentioned, based on previous findings, it is hypothesized that stimulation of CM/VL will generate ingestive behaviors, while stimulation of EM/EL will evoke aversive responses.This study employs a straightforward strategy to define the effects of taste-responsive PBN regions on oral motor behaviors. The potential impact of the project on the understanding of central processing of taste input and the function of the PBN is substantial. Specifically, elucidation of a functional topography (map) within the PBN would significantly improve the understanding of the central mechanisms producing oral motor responses to taste input.