A) Percent change in ROI mean voxel intensities of Mn2+ 24 hours after injection of 66 mg/kg MnCl2, using T1 weighted MRI scanning. The x-axis represents caudal to rostral axis of the ventrolateral medulla relative to the caudal pole of the facial nucleus (designated as FN0 and 0 μm). A pattern of increasing Mn2+ uptake was seen from the caudal to rostral levels of the RVLM (*, p<0.05, main effect). B) Pattern of increased dendritic branching from caudal to rostral areas of the ventrolateral medulla observed in bulbospinal catecholaminergic RVLM neurons from our previous study (*, p<0.05, compared to 600 μm; modified from Mischel et al., 2014). Grey boxes represent the functionally and anatomically defined region of the RVLM.