Purpose: Nicotine and caffeine are among the most frequently self-administered licit psychoactive drugs in Taiwan. This study investigated whether Daphnia pulex could be used to investigate the effects of nicotine and caffeine on the heart and to establish Daphnia as a model for investigating the role of toxins.
Methods: The toxic effects of pure nicotine and caffeine were measured and compared with the EC50 value of the mixed drugs using D. pulex acute toxicity test, chronic toxicity test, measurement of heart rate, and mixed toxicity test.
Results: The heart rate fluctuated within the first 14 days, and then it dropped dramatically on the 15(superscript th) day and hit the lowest point at experiment termination. It can be concluded that heart of water fleas may respond to low concentrations of chemicals until the 15(superscript th) day. With a Mixture Toxicity Index of 2.6, we found that combined caffeine and nicotine had a synergistic effect.
Conclusion: The impact of chemicals on D. pulex can be displayed with better clarity by incorporating heart rate analysis. The water fl ea can be studied as an indicator of the presence off environmental toxicants.
目的：尼古丁和咖啡因在台灣是屬於可以自行管理的神經興奮劑。本研究的主要目的是以圓水蚤的的心跳變化來探討尼古丁和咖啡因的毒性影響，並闡述以水蚤的模式研究環境的有毒物質。
方法：以圓水蚤微生物試驗體材，及採用純尼古丁和咖啡因藥劑進行毒性試驗，比較急毒性、慢毒性、混合毒性等試驗的半數致死數值，及測量其心跳數率的改變。
結果：本研究發現在低濃度的情況下圓水蚤的心跳有明顯的反應；在第14天以前心跳呈現不規律，到第15天其心跳則呈現急速下降直到試驗結束，因此推斷圓水蚤對低濃度的尼古丁和咖啡因的耐受閾值在第15天。有毒物質對環境的影響並非單一毒物；應該是複雜的混合毒物，以混合毒物指標2.6的尼古丁和咖啡因加成作用發現對圓水蚤的影響最大，證實圓水蚤心跳速率的分析可以做為環境有毒物質的參考。
結論：本研究結果支持先前的研究報告；圓水蚤的心跳速率可以作為藥理學探討的指標。以水蚤作為廣泛的慢毒性暴露追蹤，可比傳統的慢毒性試驗節省70%的時間。
