Pain Relief in PAP Injections (image) University of North Carolina Health Care Caption PAP (red) is found in neurons that sense pain-producing stimuli. Credit Zylka lab, University of North Carolina at Chapel Hill. Usage Restrictions None 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.