Melatonin Receptors (image) University of Southern California Share Print E-Mail Caption The sleep-promoting hormone melatonin (shown as a constellation in the night sky) is synthesized from serotonin (shown as a kite) during night time, and both of these archaic molecules predate animal evolution. High melatonin levels at night permit it to establish its sleep-promoting properties by acting through high affinity receptors, depicted in the right side of the image composition. Credit Illustration by Yekaterina Kadyshevskaya, Bridge Institute at USC Michelson Center for Convergent Bioscience. Usage Restrictions Credit Yekaterina Kadyshevskaya, Bridge Institute at USC Michelson Center for Convergent Bioscience. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.