SLC6A2 and obesity due to melanocortin 4 receptor deficiency: Our decades-long research using a norepinephrine transporter (NET)-selective radiotracer ((S,S)-[11C]O-methyl reboxetine; [11C]MRB) [51,52] has demonstrated the significant vulnerability of the LC-NE system to numerous conditions, including addiction [53], ADHD [54,55,56], obesity [57,58,59,60,61,62,63], brown fat [64,65], diabetes [66], cardiovascular dysfunction [67], and sleep disorders (review [51,52] and references cited within).