Abstract
摘要:當生物體對週遭環境突然改變的刺激,或對天敵威脅時所產生的生理反應,是有益於該生物對抗環境變化或天敵攻擊的能力基礎。這樣的生理變化即稱作逆境生理(stress physiology),且逆境生理機制在生物進化過程中扮演極重要的角色。逆境生理在脊椎動物上的研究已經有相當的歷史,且我們已經知道當身處在危機或壓力的時候,化學物質如何影響我們人類的的大腦。然而,我們對於昆蟲這種在地球上演化相當成功的動物的逆境生理反應所知甚少。昆蟲具有(相對於脊椎動物)較小且簡單的中樞神經系統,其大腦如何受到因外在的逆境刺激而產生或釋放化學物質的影響,則是一個有趣且極具挑戰性的研究課題。另一方面,昆蟲在地球上演化的成功亦顯示了昆蟲的逆境生理機制被成功地保留下來。因此本研究計劃的實驗不僅將有助於我們更深入了解昆蟲本身的逆境生理,並且可對其他研究領域(例如神經行為或演化)提供重要的生理證據。
由於目前對於昆蟲中樞神經系統與逆境刺激間的關係所知不多,所以我們以外勤蜂作為研究對象,進行初步的試驗來證明昆蟲行為與生理上的確對逆境刺激有明顯的反應:利用低溫、CO2昏迷與垂直旋轉三組逆境刺激,於覓食行為的改變上來界定是否
Abstract: Physiological reactions to a suddenly changing environment or responses to attacking by predators would be beneficial to the animals; otherwise it could lose the battle with the critical conditions or could even be eaten by its predators. Stress physiology has been intensively investigated in vertebrates. As a result, we already have several knowledge windows to see how chemicals affect the human brain. However, we almost know nothing about the stress physiology of insects, the most successfully evolved group of animal on earth. How is their tiny brain affected by chemicals of which the synthesis or release is induced by an outside critical condition, e.g. when a predator is approaching, is a challenging field to study. Insects can serve as very good experimental animal model systems for both behavioral and physiological studies, and many basic physiological systems are very well conserved in evolution. Hence, our experiments will not only contribute to a better insight in stress physiology of insects themselves, but they are likely to provide important information for other fields, such as neuroethology and evolution.
During our previous and ongoing behavioral study on honeybee workers, we found that the worker bees postponed their return to experimental food sources by more than 30 minutes if they had been anesthetized before by chilling or CO2, as compared to their normal returning that was less than 3 minutes. Without anesthetizing the worker bees, stress induced by vertical spinning also delays the workers’ returning behavior. The stressed bees did not directly go towards their hive but they seemed to loose their way to the hive. Such stressed bees also delayed their return to the feeders. Previous studies on bee memory had shown that the established pathway between bee workers’ hive and food sources is stored as a function of long-term memory. Our behavioral results suggest that the stressed bees could not find the way to their hive and back to the feeders again because they suffered from some temporal dysfunction in their long-term memory.
Further investigations with HPLC to analyze the content of octopamine, the so-called stress hormone of insects, and other biogenic amines such as dopamine and serotonin, which are considered to be stress-related neurohormones in the vertebrate brain, did reveal significant changes in the stressed bee brains. However, some as yet unknown biogenic amines and peptides (or proteins) were induced dramatically in the brains by the stress treatments. What are the stress-induced compounds, and what do they do in a stressed bee brain? Do these novel compounds play similar roles as some peptides found in a stressed human brain do? Is temporally losing memory induced by stress causally related to the appearance and action of stress-induced compounds in the brain? These are the questions for which we would like to provide answers in this proposed project.
Keyword(s)
逆境生理
蜜蜂
生物胺
多巴胺
章魚胺
血清素
stress physiology
brain
honeybee
dopamine
octopamine
serotonin