Melatonin Receptor 1-Positive (image) Neural Regeneration Research Share Print E-Mail Caption Melatonin receptor 1-positive neurons of varying sizes (arrows) were observed in orofacial pain rats. The medium and small neurons, which are related to pain, were more numerous than large neurons. Credit Neural Regeneration Research Usage Restrictions None 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.