POMC and obesity due to melanocortin 4 receptor deficiency: Global knockout of the 5-HT2C receptor (5-HT2CR) induced pronounced hyperphagia, hyperactivity, and obesity in mice, but selective re-expression of 5-HT2CRs in POMC neurons resulted in the normalization of body composition, feeding behavior, and peripheral insulin sensitivity (Xu et al., 2008, 2010a).