Scratching Mouse (VIDEO) Washington University School of Medicine This video is under embargo. Please login to access this video. Caption A mouse temporarily scratches when injected with a substance to cause itching. But mice that can't make serotonin don't scratch as much as their littermates that do make it. Credit Washington University Center for the Study of Itch Usage Restrictions None License Licensed content 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.