LEP and obesity due to melanocortin 4 receptor deficiency: These data suggest that leptin decreases mesolimbic dopamine signaling in (chow-fed) wild-type animals and increases mesolimbic dopamine signaling in leptin-impaired (obesity) models (such as the peripherally leptin resistant fcHFHS rats, leptin-deficient ob/ob mice and leptin receptor-deficient obese Zucker rats), pointing to a unique interaction between leptin-function and dopamine signaling, which is intriguing and requires further investigation.