Proopiomelanocortin Neurons Are Direct Targets for Leptin in the Hypothalamus

Leptin is a protein product of the obese (ob) gene, which is secreted by adipocytes and functions as a satiety factor to regulate food intake. The expression of the leptin receptor in several hypothalamic nuclei suggests that multiple neuronal subtypes are targets for leptin's action. Products of the proopiomelanocortin (POMC) gene are known to affect feeding behavior, and POMC neurons share a similar distribution with leptin receptor mRNA in the arcuate nucleus. We used double label in situ hybridization and computerized image analysis to test the hypothesis that POMC neurons coexpress the leptin receptor. Quantitative analysis confirmed that POMC neurons in the hypothalamus express leptin receptor mRNA. Based on this observation, we infer that POMC neurons and the products of the POMC gene may be part of the signaling pathway mediating leptin's action on feeding and perhaps other physiological functions.