Rolen S H, Caprio J
Department of Biological Sciences, Louisiana State University, Life Sciences Building Room 107 Baton Rouge, LA 70803, USA.
J Exp Biol. 2008 Sep;211(Pt 17):2786-91. doi: 10.1242/jeb.018648.
Bile salts are known olfactory stimuli for teleosts, but only a single report has indicated that the taste system of a fish was sensitive to this class of stimuli. Here, gustatory responses of the channel catfish, Ictalurus punctatus, to four bile salts that included taurine-, glycine- and non-conjugated compounds along with three stimulatory amino acids as a comparison were investigated using extracellular electrophysiological techniques. Integrated multiunit responses were obtained from the branch of the facial nerve innervating taste buds on the maxillary barbel. Bile salts were shown to be highly effective facial taste stimuli, with estimated electrophysiological thresholds for three of the four tested bile salts of approximately 10(-11) mol l(-1) to 10(-10) mol l(-1), slightly lower by 1-2 log units than those to amino acids in the same species. Although the sensitivity of the facial taste system of the channel catfish to bile salts is high, the relative magnitude of the response to suprathreshold concentrations of bile salts was significantly less than that to amino acids. Multiunit cross-adaptation experiments indicate that bile salts and amino acids bind to relatively independent receptor sites; however, nerve-twig data and single-fiber recordings suggest that both independent and shared neural pathways exist for the transmission of bile salt and amino acid information to the primary gustatory nucleus of the medulla.
胆汁盐是硬骨鱼已知的嗅觉刺激物，但仅有一份报告指出鱼类的味觉系统对这类刺激敏感。在此，利用细胞外电生理技术研究了斑点叉尾鮰对上颌须上支配味蕾的面神经分支对四种胆汁盐（包括牛磺酸、甘氨酸和非共轭化合物）以及三种刺激性氨基酸作为对照的味觉反应。从支配上颌须味蕾的面神经分支获得整合多单位反应。胆汁盐被证明是高效的面部味觉刺激物，四种测试胆汁盐中的三种估计电生理阈值约为10（-11）mol l（-1）至10（-10）mol l（-1），比同一物种对氨基酸的阈值略低1-2个对数单位。尽管斑点叉尾鮰的面部味觉系统对胆汁盐的敏感性较高，但对超阈值浓度胆汁盐的反应相对强度明显低于对氨基酸的反应。多单位交叉适应实验表明，胆汁盐和氨基酸结合到相对独立的受体位点；然而，神经小枝数据和单纤维记录表明，胆汁盐和氨基酸信息向延髓初级味觉核传递存在独立和共享的神经通路。
