However, experiments performed in mice revealed that mice lacking Lepr on POMC neurons (e.g., Pomc-Cre, Leprlox/lox mice) (Balthasar et al., 2004), on AgRP neurons (e.g., Agrp-Cre, Leprlox/lox mice) (Tong et al., 2008) and on both POMC and AgRP neurons (e.g., Pomc-Cre, Agrp-Cre, Leprlox/lox mice) (van de Wall et al., 2008) develop mild obesity, which suggests that the POMC/CART and NPY/AgRP/GABA could not be the only neurons interfacing the catabolic action of leptin. This evidence concerns the gene NPY and obesity due to melanocortin 4 receptor deficiency.