Ogawa K, Caprio J
Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
J Neurophysiol. 1999 Aug;82(2):564-9. doi: 10.1152/jn.1999.82.2.564.
We investigated the neural processing of binary gustatory mixtures of amino acids by the facial taste system of the channel catfish, Ictalurus punctatus. In vivo electrophysiological recordings indicated that the magnitude of both integrated and single-unit facial taste responses to binary mixtures of amino acids was greatest if the components bound to independent receptor sites. Facial taste responses were obtained from 32 multiunit and 55 single taste fiber preparations to binary mixtures of amino acids whose components bind to independent taste receptor sites (group I) or to the same or highly cross-reactive taste receptor sites (group II). All component stimuli were adjusted in concentration to provide approximately equal response magnitude as determined by either the height of the integrated multiunit taste response or by the number of action potentials generated/3 s of response time/single taste fiber. The mixture discrimination index (MDI), defined as the response to the mixture divided by the average of the responses to the component stimuli, was calculated for each test of a binary mixture. MDIs of group I binary mixtures for both the integrated multiunit and single fiber data were significantly greater than those for either the control or group II binary mixtures. In a subset of multiunit recordings, the MDIs of a group I binary mixture across three log units of stimulus concentration were similar and significantly greater than those of a group II binary mixture. Analysis of the single fiber data also indicated that the MDIs of group I binary mixtures were significantly larger than those of group II binary mixtures for both alanine-best and arginine-best taste fibers; however, the MDIs of group I binary mixtures calculated from recordings from arginine-best taste fibers were significantly greater than those recorded from alanine-best taste fibers.
我们研究了斑点叉尾鮰（Ictalurus punctatus）面部味觉系统对氨基酸二元味觉混合物的神经处理过程。体内电生理记录表明，如果氨基酸混合物的成分与独立的受体位点结合，那么面部味觉对氨基酸二元混合物的整合反应和单单位反应的幅度最大。从32个多单位和55个单味觉纤维制剂中获得了对面部味觉的反应，这些制剂针对的是氨基酸二元混合物，其成分与独立的味觉受体位点（I组）或相同或高度交叉反应的味觉受体位点（II组）结合。所有成分刺激的浓度都进行了调整，以通过整合的多单位味觉反应的高度或通过每个单味觉纤维在3秒反应时间内产生的动作电位数量来确定提供大致相等的反应幅度。对于二元混合物的每次测试，计算混合物辨别指数（MDI），其定义为对混合物的反应除以对成分刺激反应的平均值。I组二元混合物的多单位整合数据和单纤维数据的MDI均显著高于对照组或II组二元混合物的MDI。在多单位记录的一个子集中，I组二元混合物在三个对数单位刺激浓度下的MDI相似，且显著高于II组二元混合物的MDI。对单纤维数据的分析还表明，对于丙氨酸最佳和精氨酸最佳的味觉纤维，I组二元混合物的MDI均显著大于II组二元混合物的MDI；然而，从精氨酸最佳味觉纤维记录中计算出的I组二元混合物的MDI显著大于从丙氨酸最佳味觉纤维记录中计算出的MDI。
