這套機制極可能仰賴一氧化氮(nitric oxide, NO)可直接穿過細胞膜並向四周輻射擴散的神經傳導特性，利用NO 來調控視神經系統，以快速地適應各種不同的光環境。然而目前此一推論仍缺乏直接的生理證據。近年的研究結果發現，昆蟲周邊視覺系統具有生成NO 的能力，因此推測昆蟲的周邊視覺系統可藉由NO 進行水平與逆向的神經傳導，達到調控神經訊息處理機制的功能。為進一步了解NO 在視覺系統中的生理功能及其與光適應的關係，本研究計畫擬承襲過去對昆蟲視神經系統的研究成果，以蜜蜂的周邊視覺系統為研究模型，深入探討不同光適應狀態下視神經調控機制與NO 的關係。研究程序主要可分為三個階段：(1)使用 NO 感測電極及電生理技術，確定NO
Abstract: Accommodation to the fast changing of light environment is a fundamental but delicate
mechanism for most visual systems. Because of its transferability to cell membrane and fast spread-out in 3-D space, previous studies speculated that the neural transmitter, nitric oxide(NO), probably plays an important role to modulate the visual neural system for adapting different light conditions in the environment. However, directly physiological evidence to prove this mechanism is still needed. Recent studies on insect visual system showed that the peripheral visual system of insect should produce NO, and thus the peripheral visual system may mediate both the retrograde and horizontal signal transmission with NO as a neurotransmitter (or, a neuromodulator) to control the system. In this project, we succeed our previous physiological studies on the visual system of honeybee to further explore the neural mechanism of light adaptation and the physiological function of NO. Three approaching stages of this project are: (1) Using NO-sensitive electrode and electrophysiological techniques to determine the sources and expression timing of the NO releasing in the peripheral visual system of honeybee, and to study the function of NO to each single visual neuron. (2) Applying optical recording technique to study the NO releasing pattern the eyes are light-adapted with various light intensities and wavelengths, and to reveal the spatial and temporal interaction of NO diffusion. (3) With optical recording technique, intracellular calcium activity and NO producing and effecting changes will be visualized for our understanding the control mechanisms and their physiological relationship. These proposed studies will promise to explore the physiological function of NO within adaptation mechanisms in the insect peripheral visual system and its effects to the insect color vision.