Molecular neurobiological studies on the taste reception in Drosophila.

在果蝇中，味觉感受器神经元(GRN)位于毛状结构中，称为感受器，位于前胸腿和唇部。大多数味觉感受器有四个GRN，根据它们对基本刺激的首选敏感性而命名：水(W细胞)、糖(S细胞)、低浓度盐(L1细胞)和高浓度盐(L2细胞)。我们首次证明，前胸腿上的几个味觉感受器既通过激活特定的味觉神经元，也通过抑制糖和水激活的味觉神经元来检测苦味化合物。使用一种基于尖峰间期分析的新的统计方法，我们发现苦味化合物激活L2细胞。不同感受器对苦味化合物的敏感性不同，提示L2细胞对苦味化合物的特异性受体表达存在差异。唇形味觉按长度和位置分为L型、S型和I型三种类型。我们记录了这三种感受器对糖、盐和苦味化合物的神经反应。我们发现S和I型感受器对苦味化合物有反应。L感受器和S感受器有四个细胞，而大多数I型感受器只有两个突触。在I型感受器中，我们证明了第一个GRN对糖和低浓度的盐有反应。第二个GRN检测到一系列苦味化合物，其中士的宁是最有效的；在高浓度时也能检测到盐。两种类型的GRN都不对水产生反应

In Drosophila, gustatory receptor neurons (GRNs) occur within hair-like structures called sensilla located on prothoracic legs and labellum. Most taste sensilla house four GRNs, which have been named according to their preferred sensitivity to basic stimuli : water (W cell), sugars (S cell), salt at low concentration (L1 cell), and salt at high concentration (L2 cell). We showed for the first time that several taste sensilla on the prothoracic legs detect bitter compounds both through the activation of specific taste neurons but also through inhibition of taste neurons activated by sugars and water. Using a new statistical approach based on the analysis of interspike intervals, we showed that bitter compounds activate the L2 cell. Their sensitivity to bitter compounds was different between sensilla, suggesting that specific receptors to bitter compounds are differentially expressed among L2 cells. Labellar taste sensilla are classified into three types, l-,s-, and i-type, according to their length and location. We recorded the nerve responses from all the three types of sensilla to sugars, salts and bitter compound. We found that s- and i-type sensilla respond to bitter compounds. l- and s-type labellar sensilla possess four cells, while most i-type sensilla house only two GRNs. In i-type sensilla, we demonstratd that the first GRN responds to sugar and to low concentrations of salt. The second GRN detects a range of bitter compounds, among which strychnine is the most potent ; and also to salt at high concentrations. Neither type of GRN responds to water