On Dec. 21, 1979, Stanford Medicine pharmacologist Avram Goldstein announced the discovery of dynorphin – a chemical in the human brain 200 times more powerful than morphine that could lead to the development of powerful painkillers with fewer undesirable side effects. The study was published in PNAS.

Dynorphin is a neuropeptide involved in pain, addiction and mood regulation. It exerts its activity by binding to the kappa opioid receptor (KOP) which belongs to the large family of G protein-coupled receptors. The dynorphin peptide was discovered in 1975, while its receptor was cloned in 1993.