IVP-EMG relationships. A: IVP is plotted against mean rectified EUS-EMG activity across the 8 SCI rats that exhibited npVCs following vehicle. The plot rises to a peak around 40 mmHg, then falls. Knowing that EUS-EMG amplitude varies from rat to rat, at least in part due to variations in the separation between the electrodes and the EUS, we replotted the data in B. Here, the peak value of rectified EUS-EMG within each rat is used to normalize the rectified EUS-EMG values. This results in a plot that is fairly linear but which, except at pressures over 40 mmHg, seems to level off after 25 mmHg or so. Because all 8 rats participate in the generation of the mean up to 25 mmHg but only 2 participated at the higher pressures, we separately plotted the mean values from the rats with the 3 lowest and 2 highest peak IVPs. The result, shown C, is 2 fairly linear plots with similar slopes but different intercepts and ranges.