An Insect Model for Physiology of Taste Plasticity

这项研究旨在研究味觉发育和抑制过程中发生的生理过程。由于缺乏合适的动物模型和缺乏已知的化合物，以前关于味觉发展和改变的研究受到了严重的阻碍。我们最近在毛毛虫身上发现了依赖饮食的味觉敏感性和发育，这表明这种昆虫可能是一个理想的模型。新孵化的菜粉蝶幼虫对不能接受的植物中存在的苦味威慑物不敏感，但当它们以合适的食物植物(如卷心菜)为食时，它们会产生味觉敏感性。与此同时，以卷心菜为食的幼虫开始依赖或沉迷于特定的化学物质以继续取食。然而，当幼虫以小麦胚芽人工饲料喂养时，对威慑药物的敏感性和对刺激剂的依赖永远不会发生。在充分利用这一模式之前，需要回答两个主要问题。(1)味觉感受器在多大程度上参与了动物味觉的修饰能力？(2)小麦胚芽中哪些化合物负责味觉抑制？我们建议在选择性地从敏感幼虫身上移除已知的味觉感受器后，使用行为测试来回答这些问题。随着个体昆虫对刺激剂和威慑剂的敏感性的发展，这些受体的参与将通过来自个体昆虫味觉毛发的电生理记录来证实。行为分析也将用于监测小麦胚芽中活性化合物的分离和鉴定。这项工作有望为更详细地研究特定食物成分的分子识别以及食欲和成瘾的发展所涉及的生化过程铺平道路。如果这些味觉毛发确实参与了敏感度的变化，那么这一结果有望有助于解释人类味觉的发育和丧失。昆虫模型的可获得性可能有助于消除或减少使用高等动物进行临床试验，而有关影响昆虫选择食物的饮食经验的信息在设计新的害虫管理策略时可能具有重要的农业意义。

This research is designed to examine the physiological processes that occur during development and suppression of the sense of taste. Previous studies of taste development and modification have been severely handicapped by a lack of suitable animal models and a lack of known chemical compounds. Our recent discovery of diet-dependent taste sensitivity and development in a caterpillar suggests that this insect may serve as an ideal model. Newly hatched larvae of the cabbage butterfly are insensitive to bitter feeding deterrents present in unacceptable plants, but taste sensitivity develops as they feed on a suitable food plant such as cabbage. At the same time, larvae feeding on cabbage become dependent on, or addicted to specific chemicals for continued feeding. However, when the larvae are reared on a wheat germ artificial diet, development of sensitivity to deterrents and dependence on stimulants never occurs. Two major questions need to be answered before this model can be fully utilized. (1) To what extent are taste receptors involved in the modified ability of animals to taste? (2) What are the compounds in wheat germ that are responsible for taste suppression? We propose to answer these questions using behavioral tests after selective removal of known taste receptors from sensitive larvae. The involvement of these receptors will be confirmed by electrophysiological recordings from taste hairs of individual insects as their sensitivity to stimulants and deterrents develops. Behavioral assays also will be used to monitor isolation and identification of the active compounds from wheat germ. This work is expected to pave the way for more detailed studies of the biochemical processes involved in molecular recognition of specific food constituents as well as the development of cravings and addiction. If these taste hairs are in fact involved in sensitivity changes, the results are expected to help in explaining development and loss of taste in humans. The availability of an insect model may serve to eliminate or reduce the use of higher animals for clinical testing, and information about dietary experience that can influence food choice by insects could have significant agricultural importance in the design of new pest management strategies.