昆虫嗅觉中枢系统对外周信号的整合编码研究进展

Research progress of integrated coding of peripheral olfactory signals in the central nervous system of insects

灵敏、复杂的嗅觉对于昆虫的生存和繁殖至关重要。触角是昆虫主要的嗅觉器官,其表面覆盖着大量各种类型的嗅觉感受器,这些感受器能够感受环境中的挥发性化合物,并将感受到的化学信号转化为电信号。电信号首先经嗅觉受体神经元传递到大脑中的初级嗅觉中枢触角叶,不同来源的信号在此被初步整合加工,再经投射神经元投射到高级神经中枢蘑菇体和侧角叶,蘑菇体主要与后天的气味学习行为有关,而侧角叶主要负责先天的气味行为反应。本文以模式昆虫果蝇和鳞翅目昆虫为主,综述了昆虫嗅觉中枢系统对外周信号整合编码的研究进展。研究人员依靠黑腹果蝇Drosophila melanogaster遗传操作技术的便利在该领域取得了快速进展,系统阐释了初级嗅觉中枢对气味信息的整合与向下传递以及高级嗅觉中枢对这些信息的再次加工。由于遗传操作的限制,其他昆虫与果蝇相比研究进展较慢,目前研究主要局限于对鳞翅目昆虫中枢神经系统的结构解剖和触角叶内各类神经元的记录等。因此,我们建议展开以下研究:(1)利用模式昆虫果蝇,全面解析侧角叶对气味信息的编码,阐明其对各类气味特异行为反应的神经机制;(2)大力发展非模式昆虫的遗传操作技术,结合双光子钙离子成像等新技术,阐明重要化合物在特定害虫脑中的投射、多种信号在害虫脑中如何进行整合加工,进而产生相应的行为反应。

A sensitive and complex sense of smell is essential for the survival and reproduction of insects.Antennae are the main olfactory organs of insects and covered with a large number of different kinds of olfactory sensilla on their surface.Volatile chemicals in the environment are detected by these sensilla and subsequently transformed into electrical signals.Those signals are then transmitted through olfactory receptor neurons to the primary olfactory center of the brain,the antennal lobe,for the early processing.After processing,the signals are sent to the lateral horn which is thought to mediate innate behaviors as well as the mushroom body which is required for memory storage and retrieval.In this article,we reviewed the research progress of integrated coding of insect olfactory central system for signals from the peripheral olfactory system with focus on the Drosophila model and lepidopterans.Significant progress has been made in Drosophila melanogaster due to its advantages in genetic manipulation technology,including the propagation of information within the primary olfactory center and the subsequent processing in higher olfactory centers.Compared to Drosophila,the studies on olfactory coding of the central nervous system of other insects make tardy progress and are limited to recording and identification of the neurons in the antennal lobe of lepidopterans because of lacking genetic manipulation technology.The following aspects are suggested to be investigated in the future:(1)Olfactory coding in the lateral horn should be thoroughly investigated in the Drosophila model to further explain the neurological mechanism of olfactory behaviors;(2)Genetic tools should be developed and combined with two-photon imaging in none-model insects to elucidate the mechanism of perception,interaction,and behavioral consequence of the critical odorants.