The Opioid Receptor Colorimetric Cell-Based ELISA Kit provides a lysate-free, convenient, and high-throughput approach for sensitive detection of OpioidReceptor protein expression profile in cells. The kit can be used for measuring the relative amounts of OpioidReceptor in cultured cells as well as screening for the effects that various treatments, inhibitors (ie siRNA or chemicals), or activators have on OpioidReceptor.