Abstract
In the past 50 years, scientists have made considerable strides toward understanding how opioids act. This special issue of Molecular Pharmacology celebrates these 50 years of opioid research and the role that the International Narcotics Research Conference has played in driving this research, by bringing together review and original research articles that present historical highlights, the current state of the art, and perspectives on the future of opioid research. SIGNIFICANCE STATEMENT: Opioids have been used for thousands of years to manage pain and cause euphoria, but their use has been highly limited due to serious side effects. Deciphering the mechanisms of how opioids mediate beneficial and adverse physiological outcomes is essential for developing better treatments for pain and for opioid addiction.