Kappa Opioid Receptor Structures (IMAGE) University of Maryland School of Medicine Caption Structures of the kappa opioid receptor bound to four types of G-protein and one of two drugs. Credit University of Maryland School of Medicine Usage Restrictions No restrictions. License Public Domain 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.