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The Effects of Caffeine on Learning and Memory in Zebrafish (Danio rerio) Erica Pantelich, Department of Biology, York College INTRODUCTION: Learning and memory research uses a variety of invertebrate and vertebrate models to investigate the neural basis of cognitive function. From this research, understanding cognitive function, reasons for cognitive dysfunction, and treatments promoting cognitive improvement have been gained. Zebrafish are an emerging model for many aspects of neural function. Researchers like Levin and Chen (2001) observed the effects of nicotine on the memory of zebrafish with a delayed spatial alteration task. Carvan et al. (2004) tested the effects of ethanol on zebrafish memory through a spatial alteration task in a testing apparatus. Darland and Dowling (2001) tested wild type and mutagenzied zebrafish for learning and memory by using a T- maze. With much focus on the effects of nicotine and ethanol on zebrafish’s learning and memory, little attention has been given to the effects of caffeine. My research tested the effects of caffeine on learning and memory in zebrafish through the use of a T-maze. QUESTIONS ASKED: 1)Will caffeine enhance the learning and memory (short and/or long term) of the desirable habitat of the T-maze? 2)Will caffeine quicken a decision in a zebrafish to enter either the desirable or undesirable habitat? HYPOTHESIS : Caffeine will enhance the learning and short- term memory, but not the long-term memory of zebrafish. METHODS: Figure 1 Figure 2 Figure 3 FUTURE STUDIES: Start with many control groups to find the best methodology and sample size. Label each fish to see each individual zebrafish’s progress. Use a different testing apparatus such as a spatial alteration task to test learning and memory. ACKNOWLEDGEMENTS: I would like to thank Dr. Boehmler for her instruction with zebrafish and Dr. Rehnberg for his guidance and patience throughout my behavioral study. LITERATURE CITED: Carvan III, M.J., Loucks, E., Weber, D.N., and Williams, F.E. 2004. Ethanol effects on the developing zebrafish: neurobehavior and skeletal morphogenesis. Neurotoxicology and Teratology 26:757-768. Childs, E., and Wit, de H. 2006. Subjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine users. Psychopharmacology. 185:514-523. Darland, T., and Dowling J.E. 2001. Behavioral screening for cocaine sensitivity in mutagenized zebrafish. Proceedings of the National Academy of Science 98:11691-11696. Guo, S. 2004. Linking genes to brain, behavior and neurological diseases: what can we learn from zebrafish? Genes, Brain and Behavior 3: 63-74. Levin, E., and Chen, E. 2004. Nicotinic involvement in memory function in zebrafish. Neurotoxicology and Teratology 26:731-735. Levin, E., Limpuangthip, J., Rachakonda, T., and Peterson, M. 2006. Timing of nicotine effects on learning in zebrafish. Psychopharmacology 184: 547-552. Young zebrafish were separated equally into four tanks at random (n=13) (Figure 1). 0, 0.06mM, 0.6mM, and 6.0mM of caffeine were prepared for all 10 days of experimentation and stored in 10mL containers. The four tanks were coded to match a corresponding coded 10mL container by an assistant to ensure a blinded study. The fish were exposed to 0, 0.06, 0.6, or 6 mM of caffeine for 3 minutes every day for 10 consecutive days. Exposure took place in a 50 mL beaker. The T-maze (Figure 2) was constructed to assess learning and memory of caffeine-exposed zebrafish and included a desirable habitat and an undesirable one. After exposure, each fish was placed at the starting point of the T-maze and timed until making a decision, either the desirable or undesirable habitat. Until all fish of a tank were tested they were placed into a reserve tank and then placed back into their home tank. Data were analyzed using the binomial equation (Figure 3) and Prism software. RESULTS: P-values calculated from the binomial equation were plotted for each day for all four groups. For all four groups, the p-values did not become smaller as the days increased (Figure 4). The relationship between the number of days that had passed and the amount of time to make a decision whether left or right was plotted and analyzed through a one-way ANOVA (Figure 5). The time on Day 1 compared to the time on Day 10 is smaller, and there seems to be a decrease in time to a decision as days pass. When statistically analyzed through a one-way ANOVA, there was no significant difference in any of the groups (p>0.05). CONCLUSION: Due to the probability (p-value) to go to the desirable habitat of the four groups not becoming smaller as days increased, this showed that zebrafish did not choose to go this side more. Although the graphs display the trend that the zebrafish made a decision faster as time passed, this was not statistically supported (p>0.05). Overall, because the control group was unable to learn and remember the T-maze, the results of the caffeine groups are inconclusive. Figure 4. P-values represent the probability, calculated from the binomial equation, of choosing the desirable habitat of the T-maze at days 1-10, 13, and 17 for each group (n=13). The dashed line represents a p- value of 0.05. A=control, B=0.06mM, C=0.6mM, and D=6.0mM. Figure 5. The time it took to make a decision, whether for the desirable or undesirable side, at days 1-10, 13 and 17 of all four groups (n=13). Error bars represent the S.E.M. With the exception of the controls (A), the other groups seem to make a decision faster as time increases. However, after a one-way ANOVA of the days of each group, there was no significant difference between the days (p>0.05). A=control, B=0.06mM, C=0.6mM, and D=6.0mM.
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