PROCESSING OF TASTE MIXTURES BY BRAINSTEM NEURONS

虽然食物的味觉成分几乎总是复杂的， 混合物，大多数味觉研究，特别是神经生理学研究， 采用简单的刺激，代表了四种基本的味觉品质， 甜的、咸的、酸的和苦的。 具有不同性质的物质的混合物 味道或类似味道刺激的相互作用已经收到 电生理学家相对较少关注。 描述的研究 在这项建议中，旨在研究神经生理学， 均匀（相同质量）和非均匀（不同质量）混合物 味觉刺激。 臂旁核单个神经元的反应 将在细胞外记录仓鼠的细胞核（PbN）。 刺激会 以蔗糖、氯化钠、柠檬酸、奎宁为浓度系列 盐酸盐（QHCl）及其混合物（非均相）和蔗糖， 果糖、木糖醇和糖精钠及其混合物（均相）。 将研究三种非均质混合物：蔗糖- NaCl，蔗糖- QHCl和NaCl -柠檬酸。 均匀混合物实验将包括 蔗糖-果糖、蔗糖-糖精钠和蔗糖-木糖醇混合物。 这些刺激对是在已知混合物的基础上选择的 人类心理物理学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 一系列的每一对刺激将被提出，其次是几个 混合物系列，其中一种组分的不同浓度 将被添加到另一个的浓度系列中。 因此， 一对刺激物的浓度将被因子地组合， 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， 已经被用于电生理学和心理物理学 混合口味的研究 混合物的定量性质 每对刺激的相互作用将在神经元类型之间进行比较 在PbN中，由它们对代表 四种味觉品质。 与这些模型的偏差或 对神经元类型之间的给定混合对的响应将表明 混合物中的神经相互作用。 之间的相互压制 异质混合物，这已被注意到，在人类心理物理 研究，将与抑制反应的发生相关， 在这些三级味觉神经元中， 更多的外周细胞。 混合刺激之间的相互作用 抑制或协同作用的PbN将研究在单纤维的 鼓索神经，以进一步评估突触的贡献 处理混合现象。

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.