Contents

20 September 2013
Vol 341, Issue 6152

About The Cover

Cover image expansion

COVER Immunostained fluorescence microscopy image of a biomarker of endogenous withdrawal (phosphorylated extracellular regulated kinase, red) that increases in mouse spinal cord neurons (green) during opioid receptor blockade (image width: 250 micrometers). Inflammation or injury to the skin causes μ-opioid receptors to become constitutively active, which leads to long-term relief from chronic pain, but at the expense of endogenous opioid dependence. See page 1394. Image: Suzanne Doolen, Greg Corder, and Brad Taylor/University of Kentucky