The influence of leptin on the dopamine system and implications for ingestive behavior.

Food intake is regulated by many factors, including sensory information, metabolic hormones and the state of hunger. In modern humans, the drive to eat has proven to be incompatible with the excess food supply present in industrialized societies. A result of this imbalance is the dramatically increased rates of obesity during the last 20 years. The rise in obesity rates poses one of the most significant public health issues facing the United States and yet we do not understand the neural basis of ingestive behavior, and specifically, our motivation to eat. Understanding how the brain controls eating will lay the foundation for systematic dissection, understanding and treatment of obesity and related disorders. The lack of control over food intake bears resemblance to drug addiction, where loss of control over behavior leads to compulsive drug use. Work in laboratory animals has long suggested that there exist common neural substrates underlying both food and drug intake behaviors. Recent studies have shown direct leptin effects on dopamine neuron function and behavior. This provides a new mechanism by which peripheral hormones influence behavior and contribute to a more comprehensive model of neural control over food intake.