Getty Images An ancient lineage of jawless fish similar to eel called lamprey was the key to successful experiment published in Neuron. Researchers looking to help people suffering from addiction, depression, and pain are studying how certain brain neurons operate to see if they can be controlled. In a paper published May 11 in Neuron, researchers at the University of Washington School of Medicine and Washington University in St. Louis, along with several other universities, successfully used a protein called parapinopsin to turn off brain circuits. This protein is found in lamprey – an ancient lineage of jawless fish similar to eel.