ECG recordings at neonate and adult time points. A) Tracing of representative ECG recordings from PND2 neonate FVB/N mice. All graphs show some tremor of the isoelectric line due to the mouse being conscious and unrestrained. B) Tracing of representative adult mouse ECG readings. Note the development of a slower adult heart rate in female (bottom) as compared to male (top) mice. P, Q, R, S, and T waveforms are denoted by their individual letters. Scale Bar = 100 ms.