Following Drs. Zagon and Mclaughlin’s discovery of the growth-slowing effects of Low Dose Naltrexone and the growth-accelerating effects of high dose Naltrexone, they set about to discover the price molecular interaction which led to this behavior. This led to the discovery that a natively-produced endorphin, met-enkephalin, was responsible for the regulation of cellular growth.

In order to symbolize and emphasize its action in relation to control of growth of cells, Dr. Zagon and his team renamed this as Opioid Growth Factor or OGF.They further discovered that the effect of OGF is mediated by a receptor. Originally named the zeta receptor because it was thought to be a new member of the opioid receptor family, recent cloning and sequencing of this receptor has demonstrated that it is not like classical opioid receptors. The receptor for OGF was renamed the Opioid Growth Factor receptor (OGFr).

Since then numerous studies have been carried out by Dr. Zagon and his team to determine the biological effects of production of OGF and its interaction with OGFr.