Studies in rats show that chronic hyperprolactinemia induced by regular injections of dopamine antagonists or exogenous prolactin, or ectopic pituitary transplants, is associated with increased food intake and body weight (5–7), whereas pharmacological suppression of prolactin secretion with the dopamine-agonist bromocriptine evokes the opposite outcome, being most effective in lactating rats and least in males (8). The gene discussed is PRL; the disease is hyperprolactinemia.