Expression of leptin receptor mRNA in the hypothalamic arcuate nucleus--relationship with NPY neurones.

The obese phentotype of ob/ob mice is linked to a mutation in the ob gene that results in expression of a truncated inactive protein. The ob gene product, leptin, is synthesized in adipose tissue and is a circulating factor that regulates body weight. Leptin receptors were recently cloned and a mutation in the leptin receptor gene in obese db/db mice was identified. Leptin receptor mRNA has been detected in brain, including hypothalamus, but the cellular localization has so far not been clarified. Here we report on the cellular localization of leptin receptor mRNA in the mouse brain using in situ hybridization. Strong hybridization was observed in the choroid plexus and hypothalamic arcuate nucleus. Weaker hybridization was detected in the hippocampal formation and in the cerebral cortex. Within the arcuate nucleus, cell bodies expressing leptin receptor mRNA were distributed in its ventromedial subdivision. Hybridization of semiadjacent sections with a probe to neuropeptide Y (NPY) showed a co-distribution of labelled cell bodies, suggesting the presence of leptin receptors on NPY-containing neurones.