探討Kryptolebias marmoratus獲得輸贏經驗後體內雄性激素、雌性激素、皮質醇與血清素受器基因表現量逐時變化情形

Temporal Changes in Androgen, Estrogen, Cortisol and 5-HT1A Receptor Gene Expression after Wins and Losses in Kryptolebias marmoratus

李誠裕(Cheng-Yu Li)

指導教授 ： 許鈺鸚

國立臺灣師範大學/理學院/生命科學研究所/碩士(2011年)

摘要

許多動物的打鬥呈現出一個共同的現象，亦即前次打鬥之勝、負經驗會提升或降低個體在後續打鬥中的攻擊性與獲勝機率，稱之為勝者、敗者效應。由於動物的攻擊性被發現與神經內分泌系統有密切的關係，因而勝者、敗者效應也被認為應受到神經內分泌系統之調控。先前的研究顯示Kryptolebias marmoratus之打鬥行為呈現出明顯的勝敗者效應，而且其打鬥行為與睪固酮(testosterone)和皮質醇(cortisol)分泌量有顯著的關聯；然而，此魚之勝敗者效應卻非經由這些荷爾蒙或雌性激素(estrogen)、睪丸硬甾酮(11-ketotestosterone)等之分泌量所調控形成。由於荷爾蒙除了分泌量的變化外，其受器蛋白的表現量多寡亦會影響個體之攻擊性與打鬥行為，因此我於本研究中探討個體在獲得勝、敗或者控制經驗後，其腦部與生殖腺體之雄性激素受器(androgen receptor)、雌性激素α/β 受器(estrogen α/β receptor)、血清素1A 受器(5-HT1A receptor)與葡萄糖皮質素受器(glucocorticoid receptor)等受器基因表現量是否有所差異。實驗結果顯示，擁有三次落敗經驗的個體，其腦部之雄性激素受器基因與生殖腺之雌性激素α受器基因表現量顯著低於擁有一次控制經驗的個體；而在其他受器基因表現量上，各經驗處理組間並無顯著差異。由於贏的經驗與一次落敗經驗並未顯著的影響任何受器基因表現量，本研究結果顯示這些受器基因表現量應非此魚之勝、敗者效應之主要調控機制。然而本研究之其他分析顯示，接受落敗經驗處理的個體，其基礎睪固酮分泌量與個體在接受第一次落敗經驗訓練時的攻擊性行為(先開鰓蓋展示機率與打鬥持續時間)呈現顯著的正相關；而腦部受器基因表現量(雄性激素受器除外)也與個體在接受第一次經驗訓練時之攻擊性行為(先展示機率、先開鰓蓋展示機率、打鬥持續時間)呈現顯著正相關。這些結果顯示此魚之攻擊性仍與荷爾蒙以及荷爾蒙/血清素受器有密切的關係。因此，整體而言，本研究顯示荷爾蒙以及荷爾蒙/血清素受器雖然與此魚之攻擊性有密切的關係，卻非此魚展現勝、敗者效之主要生理機制。

關鍵字

勝者效應 ； 敗者效應 ； 荷爾蒙受器 ； 血清素受器 ； 打鬥行為 ； 紅樹林鱂魚

並列摘要

Recent winning/losing experiences can increase/decrease an individual's aggressiveness and its probability of winning subsequent contests, phenomena referred to as winner/loser effects. Winner and loser effects are probably mediated by the neuroendocrine system because animals’ aggression is closely associated with this system. Kryptolebias marmoratus displays winner and loser effects and its contest behaviors are associated with testosterone and cortisol levels. It appears, however, that neither winner nor loser effects are mediated by changes in the levels of testosterone or cortisol in this fish. Because hormone receptors could also modulate the effect of hormones on behavior, in this study I investigated associations in this fish between androgen receptor, estrogen α/β receptor, 5-HT1A receptor and glucocorticoid receptor gene expression levels and winning and losing experiences. The results showed significantly reduced expression levels of androgen receptor genes in the brains and estrogen α receptor genes in the gonads of individuals with three losing experiences. None of the experience treatments led to differences in brain or gonad estrogen β receptor, 5-HT1A receptor or glucocorticoid receptor gene expression levels. These results did not establish hormone/serotonin receptors to be the primary physical mechanism underlying winner and loser effects. Nonetheless, in those individuals assigned losing experience(s), the baseline hormone (testosterone) levels and the receptor gene expressions levels (except androgen receptor) were positively correlated with aggressive behavior (initiating displays, initiating gill displays and contest duration) in the 1st experience training. These results did demonstrate a relationship between fighting experience and hormones and hormone/serotonin receptor gene expressions. I concluded from these findings that although hormones and hormone/serotonin receptors have important associations with the fish's aggressiveness, they are not the major physiological mechanisms underlying winner or loser effects in this fish.

並列關鍵字

winner effect ； loser effect ； hormone receptor ； 5-HT1A receptor ； contest behavior ； Kryptolebias marmoratus

參考文獻

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