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Results
As each heart beat at a different rate in Dulbecco's Eagle Medium, the number of beats produced in the DMEM control after one minute was used as the base rate (BR) for each heart. The base rates were consistently higher than those obtained in Howard Ringers (HR) Solution (Table 1). All hearts in both groups beat faster than their base rates when transferred to the 0.1 mg/ml caffeine solution (Tables 1, Table 2). The 0.2 mg/ml caffeine solution further increased beats per minute in group B (Table 1). The 0.3 mg/ml caffeine solution caused the hearts to beat above the base rate, but it clearly did not have as great an effect on the hearts as the solutions with lower concentrations of caffeine.

Table 1. The heart beats per minute of each heart tested in DMEM, HR solution and the caffeine solutions of concentrations 0.1mg/ml, 0.2 mg/ml and 0.3 mg/ml. The reaction of each heart to the various solutions is also shown as the percentage of the base rate (DMEM).
 Group B DMEM HR 0.1 mg/ml % of BR 0.2 mg/ml % of BR 0.3 mg/ml % of BR Heart 1 72 36 78 108.3 84 116.7 66 91.7 Heart 2 65 41 78 120.0 70 107.7 68 104.6 Heart 3 38 36 37 97.4 45 118.4 46 121.1

Group A tested the effects of the higher caffeine concentrations, 0.5mg/ml and 1.0 mg/ml (Table 2). Dosages of 0.5 mg/ml caffeine decreased the heart rates below that of the base rate. When the hearts were placed in an even higher concentration of caffeine, the 1.0 mg/ml caffeine solution, beating ceased.

Table 2. The results of Group A, the average number of beats per minute when the four hearts were placed in DMEM control, and three caffeine solutions of concentrations 0.1mg/ml, 0.5 mg/ml and 1.0 mg/ml.
 Group A Average Number of bpm Percentage of BR DMEM (base rate) 32 100 0.1 mg/ml Caffiene 43 134.4 0.5 mg/ml Caffeine 19 59.4 1.0 mg/ml Caffeine 0 0.0

Results Movies:

Figures 2-6 (group A)

Figure 7-11 (group B)

© Cebra-Thomas, 2001
Last Modified: 7 May 2004

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