PROCESSING OF TASTE MIXTURES BY BRAINSTEM NEURONS

尽管食物的味觉成分几乎总是以复杂的形式出现 混合，大多数关于味道的研究，特别是神经生理学工作， 采用了简单的刺激，代表了四种基本的口味品质 甜、咸、酸、苦。不同物质的混合物 味觉或相似味觉刺激的相互作用 电生理学家的关注相对较少。这些研究描述了 在这项建议中旨在研究神经生理学的 同质(同质)和异质(异质)混合物 味觉刺激。臂旁核单个神经元的反应 仓鼠的核(PBN)将被细胞外记录。刺激物会 蔗糖氯化钠、柠檬酸和奎宁的铍浓度系列 盐酸盐(QHCl)及其混合物(非均相)和蔗糖， 果糖、木糖醇和Na-糖精及其混合物(均质)。 将研究三种非均相混合物：蔗糖-氯化钠，蔗糖-氯化钠，蔗糖- QHCl和氯化钠-柠檬酸。均匀混合实验将包括 蔗糖-果糖、蔗糖钠-糖精和蔗糖-木糖醇混合物。 这些刺激对是基于已知的混合物来选择的 人类心理物理研究或电生理学研究中的相互作用 鼓索神经的研究。对于给定的细胞，浓度 将介绍一对刺激中每一个的系列，然后是几个 混合物系列，其中一种成分的不同浓度 将被添加到另一个的浓度序列中。因此，有几个 一对刺激的浓度将进行阶乘组合，以便 单个PBN神经元的反应可以相对于 根据刺激-受体相互作用的几种模型做出的预测， 在电生理和心理物理方面都得到了应用 对混合口味的研究。混合物的数量性质 每对刺激的交互作用将在不同类型的神经元之间进行比较 在PBN中，由它们对代表 四种口味品质。与这些模型的偏差或 对给定的神经元类型混合对的反应将暗示一个角色 用于混合物中的神经相互作用。两个国家之间的相互压制 非均相混合物，这在人类心理物理学中已经被注意到 研究将与抑制性反应的发生相关， 在这些三级味觉神经元中更常见的是 在更多的外周细胞中。混合刺激之间的相互作用 PBN中的抑制或协同作用将在单个纤维中进行研究 进一步评估鼓索神经对突触的贡献 对混合现象的处理。

Although the gustatory components of food almost always occur as complex mixtures, most research in taste, particularly the neurophysiological work, has employed simple stimuli, representing the four basic taste qualities of sweet, salty, sour and bitter. Mixtures of substances with different tastes or the interaction of similar-tasting stimuli has received relatively little attention by electrophysiologists. The studies described in this proposal are designed to investigate the neurophysiology of homogeneous (same quality) and heterogeneous (different quality) mixtures of taste stimuli. The responses of single neurons in the parabrachial nuclei (PbN) of the hamster will be recorded extracellularly. Stimuli will be concentration series of sucrose NaCl, citric acid, and quinine hydrochloride (QHCl) and their mixtures (heterogeneous) and sucrose, fructose, xylitol, and Na-saccharin and their mixtures (homogeneous). Three heterogeneous mixtures will be studied: sucrose - NaCl, sucrose - QHCl, and NaCl - citric acid. Homogeneous mixture experiments will include sucrose - fructose, sucrose - Na-saccharin, and sucrose - xylitol mixtures. These stimulus pairs were selected on the basis of known mixture interactions in human psychophysical studies or in electrophysiological studies on the chorda tympani nerve. For a given cell, concentration series for each of a pair of stimuli will be presented, followed by several mixture series, in which different concentrations of one of the components will be added to the concentration series of the other. Thus, several concentrations of a pair of stimuli will be combined factorially so that the responses of individual PbN neurons can be assessed relative to predictions made from several models of stimulus-receptor interactions, which have been used in both electrophysiological and psychophysical studies of taste mixtures. The quantitative nature of the mixture interaction for each pair of stimuli will be compared across neuron types in the PbN, defined by their response profiles to stimuli representing the four taste qualities. Deviations from these models or differences in the response to a given mixture pair between neuron types will suggest a role for neural interactions in the mixtures. The mutual suppression between heterogeneous mixtures, which has been noted in human psychophysical studies, will be correlated with the occurrence of inhibitory responses, which are more frequently seen in these third-order gustatory neurons than in more peripheral cells. Interactions among stimuli showing mixture suppression or synergism in the PbN will be studied in single fibers of the chorda tympani nerve to further assess the contribution of synaptic processing to mixture phenomena.