This confocal image of normal brain tissue from the thalamus is stained with antibodies to receptors for orexin (red). Orexins are peptide hormones that help keep us awake and alert, and may also stimulate the appetite. They are produced in the hypothalamus and act through their receptors located in the nuclei of cells in many different parts of the brain. The green stain highlights the neurofilaments and the blue stain, the nuclei. A drug called orexin-RA-1 that blocks the action of these receptors is currently under development as a sleeping pill. It may also have the effect of reducing the appetite.