Figure 6. (A) Original³¹Phosphorus nuclear magnetic resonance (NMR) spectroscopic spectra from a saline (S)-treated animal. Note the increase in inorganic phosphate (Pi) and the decrease in phosphocreatine (PCr) peak area during pacing. ATP = adenosine triphosphate. (B) Similar original spectra from an animal treated with aminophylline 40 mg/kg (A40). Note minimal change in Pi and PCr peaks during pacing compared with the resting state. ATP presents as 3 individual peaks (gamma, alpha, and beta). Because quantitative changes are the same for the individual peaks, only beta-ATP peak area is analyzed. Amn = aminophylline.