MC4R and Hepatic steatosis: Given that 5-HT in the brain has been reported to suppress appetite by acting on HTR2C in the hypothalamus via the MC4R signaling pathway and that peripheral 5-HT does not cross the blood brain barrier (Lam et al., 2010), the expression of 5-HT and HTR2C in the hypothalamus, with or without autonomic nerve blockade, was analyzed to examine whether 5-HT in the brain contributes to hepatic steatosis development in the mouse models.