Caffeine The most commonly used pharmacologic substance. Caffeine increases heart rate during sleep (Bonnet, et. al. 2005) Caffeine increases blood pressure, stroke volume, and cardiac output (Hartley, et. al. 2004).
Why Does Caffeine Do This? Caffeine blocks adenosine on the surface of the heart causing higher HR. Adenosine is an antiarrythmic agent. Caffeine also inhibits enzymes that play a role in “turning off” stimulatory signals.
Purpose To determine the effects of various concentrations of exogenously added caffeine on the 4-day in vitro chicken embryo heart.
Hypothesis The effects of exogenously added caffeine at various concentrations to the in vitro 4-day chicken embryo heart will greatly increase the heart rate (bpm). Figure 4- Chicken Embryo
Methods Prepared a stock 2% caffeine solution. Then serial diluted the solution with chick saline to yield concentrations of 0.02, 0.002, 0.0002.
Methods Windowed a 4-day chick embryo according to the methods of Cruz, et. al., 1993. Determined the in vivo heart rate. Explanted the 4-day chick embryo according to the methods of Cruz, et. al., 1993. http://www.lv.psu.edu/jxm57/biol240.htm l#labsyl Figure 5- Windowed Egg
Methods Application of Caffeine Administered 3 mL of each dilution to the in vitro chick embryo using the least concentration first. Determined the in vitro heart rate of the chick embryo. Repeated these steps in the order of increasing concentration. Repeated these methods on at least six embryos.
Control The in vivo and in vitro heart rates of a 4-day chick embryos before caffeine is exogenously applied. Figure 6- In Vitro Chicken Embryo
Data Interpretation In vivo heart rate is higher than the in vitro heart rate. 5 out of 7 embryos had an increase in heart rate between in vitro w/o solution to in vitro with 0.0002. 3 out of 7 embryos had an increase in heart rate between in vitro with 0.0002 and in vitro with 0.002. Arrhythmias were noted, mostly tachycardia and atrial flutter.
Conclusion Data did not support the hypothesis. Although the initial concentration caused an increase in heart rate, higher concentrations of caffeine did not always result in a higher heart rate. Overall trend showed a decrease in heart rate.
Future Experiments After applying caffeine, incubate embryo, until it has fully developed to see if there were any adverse effects on the overall development of the chicken.
Questions Thank you for listening to my presentation. Are there any questions? Figure 8- Caffeine Molecule
References “Adenosine”. 2006. Wikipedia Foundation Inc. 22 March 2006. Bonnet, Michael, Ph.D., Manuel Tancer, M.D., Thomas Uhde, M.D., Vikram K. Yeragani, M.D. “Effects of caffeine on heart rate and QT variability during sleep.” Depression and Anxiety. 2005. Vol. 22, Issue 3. pgs 150-155. Cruz, Y.P. 1993. Laboratory exercises in developmental biology. Academic Press, San Diego, California, 241 pages. [ISBN 0-12-198390-0] [book] Hartley, Terry, Lovallo, Wiliam, Whitsett, Thomas. “Cardiovascular Effects of Caffeine in Men and Women.” The American Journal of Cardiology. 2004. Vol. 93. pgs. 1022-1026. Hebert, Terry. “Re: How, and why does caffeine affect the rate of a daphnia’s heart rate?”. 1999. MadSci Network. 22 March 2006. McLaughlin, Jacqueline and McCain, Elizabeth. Development and Physiological Aspects of the Chicken Embryonic Heart. 1996. 12 Feb. 2005.